Tube Lens Test Final Results

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by RobertOToole »

The final complete Tube Lens Test of 18 lenses is now online.

The best performer overall is still the Thorlabs ILT200 but there were some big surprises since my earlier post:(http://www.photomacrography.net/forum/v ... hp?t=37740)

There were some big unexpected results. Some of the lenses, to my surprise, performed much better when focused past infinity or short focused.

This is the link to the full test:https://www.closeuphotography.com/tube-lens-test

Hope you find the results useful. Comments and questions are welcome.

Setup:

Objective: Mitutoyo 5x M Plan APO

Camera: Sony A6300, model ILCE-6300, also known as the A6300

Sensor size: 23.5 × 15.6 mm. APS-C. 28.21 mm diagonal. 3.92 micron sensor pitch

Flash: two Godox TT350s wireless flash units, one Godox X1s 2.4G wireless flash transmitter

Vertical stand: Nikon MM-11 with a Nikon focus block

Final lens test list:

Thorlabs ITL200 Tube Lens

Mitutoyo MT-1 Tube lens

Nikon MXA20696 Tube Lens

Reichert Microscope Tube Lens

Canon 250D Close-up Lens

Century Precision Optics +4 Achromatic Diopter Lens

Century Precision Optics +7 Achromatic Diopter Lens

Cosina MMA Matched Macro Adapter Lens

Raynox +4.8 diopter

Raynox +5.9 diopter

Raynox +8 diopter

Sigma LSA Life Size Attachment Lens

Asahi Pentax Tele-Takumar 200mm f/5.6

Carl Zeiss Tele-Tessar T* 200mm f/3.5

Nikkor 135mm f/3.5 Ai

Nikkor 200mm f/4 Ai

Sigma 150mm F2.8 EX DG OS HSM APO Macro

Voigtlander APO-Lanthar 125mm f/2.5

Click on any image open a full size version.

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This is the full un-cropped image at 5x with the 100% crop areas outlined in blue.

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The results from the Sigma 150 OS was a pleasant surprise! Perfect CA correction and sharp edge to edge.

Image

The Voigtlander 125mm APO-Lanthar was also excellent but I have to mention that the lack of tripod mount collar is a big negative for me (The Sigma 150 does have a tripod collar).

Image

APO-like CA correction for $49. The 135mm f/3.5 Ai Nikkor is one of best lenses and is much cleaner image quality than the 200/4 Ai.

Image

Sigma Normal mount.

Image

Sigma reversed with short (beyond infinity) focus. The cropping will change with the short focus images.

Image

The Century +4 normal mount. Very good performance.

Image

The Century +4 even better with short focus and 110mm between the lens and objective.

Image

Thorlabs ITL200 normal mount.

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Thorlabs ITL200 short focus.

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Raynox 208mm Normal mount. Excellent.

Image

Raynox 208mm short focus. Excellent +.

Notes:

Some of the lenses in this test were tested with multiple samples, I test three ITL200s and four Sigma LSAs for example. I did not see any variation between samples.

Some of the lenses were tested with short focus, normal focus, minimum objective extension, 50mm extension and 110mm extension in both normal and reverse.

Over the course of this test I shot something like 1400 frames.

Short focus, or using a lens with less extension than is needed for infinity focus means that it is "focused" beyond infinity. This would create an unusable blurry image, but in many cases this happens to work well with tube lenses - as described here. Short focus results in the shorter "effective focal length" used here for magnification calculation purposes, so for example the Raynox +4.8, 208mm lens, with short focus is a 178mm effective FL lens, this would give you .859 x the Mitutoyo objectives marked magnification, for the Mitutoyo 5x M Plan lens this would be 4.29x.

In most cases compared to a down-sized normal focus image, the short focus image is sharper, clean and more detailed.

For more info, images, notes and comments see the post in my site, link at the top of the page.

Be sure to share any comments, questions below.

Thanks.

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by RobertOToole »

Forgot to thank Chris S, Chris R and Saul for making the test possible, thanks Guys!

Also this is important:

THE BEST AT 200MM

Excellent

Thorlabs ITL200 Tube Lens [infinity] - 9.3 - Overall best at 200mm

Century Precision Optics +4 Achromatic Diopter Lens [pushed down with short extension] - 9

Raynox +4.8 diopter - 8

Good

Sigma LSA Life Size Attachment Lens - 7.6

Reichert Microscope Tube Lens - 7

THE WORST AT 200MM

Average

Mitutoyo MT-1 Tube lens - 6.5

Nikkor 200mm f/4 Ai - 6

Nikon MXA20696 Tube Lens - 5.5

Asahi Pentax Tele-Takumar 200mm f/5.6 - 5

Carl Zeiss Tele-Tessar T* 200mm f/3.5 - 5

THE BEST TUBE LENSES SHORTER THAN 200MM

Excellent

Thorlabs ITL200 Tube Lens [pushed down with short extension] - 9.6 - Overall best at shorter than 200

Raynox +4.8 diopter [pushed down with short extension] - 9.6

Sigma 150mm F2.8 EX DG OS HSM APO Macro - 9.5

Voigtlander APO-Lanthar 125mm f/2.5 - 9.5

Raynox +8 diopter - 9.5

Nikkor 135mm f/3.5 Ai - 9

Century Precision Optics +7 Achromatic Diopter Lens - 8.5

Raynox +5.9 diopter - 9.5

THE BEST TUBE LENSES LONGER THAN 200MM

Excellent

Century Precision Optics +4 Achromatic Diopter Lens - 8.5 - Overall best at 200mm+

Average

Cosina MMA Matched Macro Adapter Lens - 5.3

THE WORST LENS LONGER THAN 200MM

Poor

Canon 250D Close-up Lens - 4

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mjkzz

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by mjkzz »

wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

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RobertOToole

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by RobertOToole »

mjkzz wrote:wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

Hi Peter,

Yes.

Sensor to shoulder of the Raynox: 144 mm extension

Normal mount

Extension from tube lens to objective: 50mm

Effective focal length (used to calculate magnification): 178mm

Effective magnification factor: 0.859 x

I have mounting and set-up for all the lenses on the my site but I can post any info anyone asks for here also.

Robert

Last edited by RobertOToole on Tue Aug 21, 2018 5:45 pm, edited 1 time in total.

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RobertOToole

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mjkzz wrote:wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

This might be more clear for people.

BTW I tested this lens in 9 different configurations and this was the sharpest and cleanest.

Image

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mawyatt

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by mawyatt »

Robert,

You (with the help from Saul, ChrisS, ChrisR) have done another superb job of helping us folks out with this informative lens evaluation.

Now I need some time to digest all this useful information.

Hat's off to you, and your helpers :D

Best,

Last edited by mawyatt on Wed Aug 22, 2018 7:42 pm, edited 1 time in total.

Research is like a treasure hunt, you don't know where to look or what you'll find!

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This is fantastic and very surprising!! I am especially glad to see that many of the tube lenses can be pushed way down. That's a game-changer for many of us, who always dreamed of a non-vignetting zoom tube lens. Seems we always had them right under our noses!

Lou Jost

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mawyatt

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Robert,

With the Raynox 150 & others, did you find the 144mm & 50mm spacing critical? Also wondering if this spacing configuration is unique to the Mitty 5X, or if the Mitty 10 and 20X would benefit as well?

Thanks again for all the efforts put forth.

Best,

Research is like a treasure hunt, you don't know where to look or what you'll find!

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mjkzz

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RobertOToole wrote:

mjkzz wrote:wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

Hi Peter,

Yes.

Sensor to shoulder of the Raynox: 144 mm extension

Normal mount

Extension from tube lens to objective: 50mm

Effective focal length (used to calculate magnification): 178mm

Effective magnification factor: 0.859 x

I have mounting and set-up for all the lenses on the my site but I can post any info anyone asks for here also.

Robert

So, we really do not care the requirement of focusing to infinity by infinite corrected objective? Very interesting! Thanks

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RobertOToole

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mawyatt wrote:Robert,

With the Raynox 150 & others, did you find the 144mm & 50mm spacing critical? Also wondering if this spacing configuration is unique to the Mitty 5X, or if the Mitty 10 and 20X would benefit as well?

Thanks again for all the efforts put forth.

Best,

Hi Mike,

Good question. the spacing was important, but its complicated.

For the test I ran most lenses (except for the telephotos) with minimal, or adapters only, then with a 50mm tube, a 75mm tube and finally with a 110mm tube between the TL and the Objective. Some but not all lenses seemed to respond to these changes, I noted this for each lens in the full test on my site.

The 144 or 145mm distance was convenient, this happened to be the length of a short tube, the body adapter and the camera register. I did not try extremes with spacing since I had such a large group of lenses.

Now this is where it gets complicated. The tube to objective distance is important.

When I short focus or focus past infinity (where the effective focal length drops so the magnification drops a bit) I had to run the lens to distance spacing tests again since image quality changed with some. This is why I had to test each lens so many times, some I had to run 7-9, even 10 times in different configurations.

When I ran a lens with short focus the magnification was pushed down, but if I increased lens to objective distance the magnification went back up a bit.

Also I did have a chance to run two other objectives with similar set-ups, one a Nikon S Fluor, and it did seem to respond in the same way but Nikon being Nikon the extra CAs and small image circle didn't make the best comparison images so I cut the test short but the Nikon objective did respond in the same way. The S Fluor and ITL200/Raynox with a short focus looked excellent.

I do plan to run a 10x and 20x at a later date for sure. I will probably run a Mity 10x first against a couple Nikon 10x objectives and then with the best tubes at different configurations.

Thanks for the questions.

Best,

Robert

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RobertOToole

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mjkzz wrote:

RobertOToole wrote:

mjkzz wrote:wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

Hi Peter,

Yes.

Sensor to shoulder of the Raynox: 144 mm extension

Normal mount

Extension from tube lens to objective: 50mm

Effective focal length (used to calculate magnification): 178mm

Effective magnification factor: 0.859 x

I have mounting and set-up for all the lenses on the my site but I can post any info anyone asks for here also.

Robert

So, we really do not care the requirement of focusing to infinity by infinite corrected objective? Very interesting! Thanks

Hi Peter,

You do want infinity focus if you want to keep the marked magnification. For image quality, no.:D

The short focus images look cleaner so I checked to see what the difference is, if any, if I re-size the the infinity focus to match the short focus image. So I converted two RAW files and re-sized the infinity image down and the short focus image had better fine detail.

Robert

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mjkzz

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RobertOToole wrote:

mjkzz wrote:

RobertOToole wrote:

mjkzz wrote:wow, thanks Robert.

However, I'd like to learn how to push down a Raynox +4.8 tube lens in the following statement? Thanks.

Raynox +4.8 diopter [pushed down with short extension] - 9.6

Hi Peter,

Yes.

Sensor to shoulder of the Raynox: 144 mm extension

Normal mount

Extension from tube lens to objective: 50mm

Effective focal length (used to calculate magnification): 178mm

Effective magnification factor: 0.859 x

I have mounting and set-up for all the lenses on the my site but I can post any info anyone asks for here also.

Robert

So, we really do not care the requirement of focusing to infinity by infinite corrected objective? Very interesting! Thanks

Hi Peter,

You do want infinity focus if you want to keep the marked magnification. For image quality, no.:D

The short focus images look cleaner so I checked to see what the difference is, if any, if I re-size the the infinity focus to match the short focus image. So I converted two RAW files and re-sized the infinity image down and the short focus image had better fine detail.

Robert

I can still focus to infinity using Raynox 250 with Mitutoyo 5X by setting Raynox 250 at the right position from the sensor, and this configuration has less than marked 5X, 3.125 to be exact (5*125/200= 3.125)

Robert wrote:When I ran a lens with short focus the magnification was pushed down, but if I increased lens to objective distance the magnification went back up a bit.

The other interesting thing is when you change distance between objective and tube lens, magnification changes, too. That runs contrary to design of infinity obj, but of course, if the tube lens is not focused to infinity, anything can happen.

And of course, your experiments show otherwise. Great work, thanks for results.

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Adalbert

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by Adalbert »

Hello Robert,

Thank you for this excellent test!

May I assume that your results (based on Mitutoyo 5x M Plan APO) are valid for NIKON LU PLANs too?

BR, ADi

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mjkzz wrote:

I can still focus to infinity using Raynox 250 with Mitutoyo 5X by setting Raynox 250 at the right position from the sensor, and this configuration has less than marked 5X, 3.125 to be exact (5*125/200= 3.125)

The Raynox 250 was one of the best in the test! If I remember correctly the 250 was pushing the corners, there was a drop-off on APS-C so I did not try to short focus the 250.

The voigtlander 125 SL had perfect corners but I don't think many people are going to pay $1800 for a tube lens or happen to have one lying around :)

BTW I finished a 3x test with three 4x objectives pushed down vs 4 lenses, that one is coming soon.

Robert

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Adalbert wrote:Hello Robert,

Thank you for this excellent test!

May I assume that your results (based on Mitutoyo 5x M Plan APO) are valid for NIKON LU PLANs too?

BR, ADi

Hi ADi,

I tried a Nikon 4x S Fluor and the results were similar and the Raynox and ITL200 short focus worked great. So I would expect the LU to behave the same way.

As soon as I can make some time I plan to run a 10X LU Plan Nikon vs Mity 10X M Plan with different tubes configurations.

Thanks for the interest.

Best,

Robert

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Oh my...

Thank You Robert!!!

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Hi Robert;

You are awesome as always!

Regards.

Omer

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Great piece of work. It's a relief to all that some of the best results come from some of the cheaper options :D. Discovering that using "wrong" orientation and "wrong" distances was remarkable.

Chris R

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kaleun96

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Really appreciate all the testing you do Robert. Coming across your website a few months ago first got me on this addictive train ride that is >2x macro photography!

I'm having a little trouble understanding how you calculate effective focal length in these tests. I tried searching the forum and google but without much success.

Most of what was on Google related to the difference between front/back focal lengths as calculated from the front/back of the lens element, whereas effective focal length was calculated from the middle...or something along those lines. Though it doesn't seem to me that this definition relates to what we're talking about here, where we're reducing the tube length from the ~160mm (+flange depth) to the 144mm in the tests.

For example I can't work out how the focal length of the DCR-150 then changes from 208mm to 178mm (effective). Any pointers would be greatly appreciated!

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My take on that - Robert's may well be different:

The FL of a lens is the same, either way round.

What seems to get called back/rear focal length and front focal length are clearances really, nothing to do with focal length!

Some of these lenses are a little bit telephoto, so the measured distances change when you reverse them.

If you use a 208mm FL lens only 178 or whatever from a sensor, it can't focus, right? Well it does if you stick another lens in front of it. The rays between the "tube" lens and the objective aren't parallel, so performance should be all messed up, but somewhat bafflingly, Robert discovered that's the way some of them work best. :smt017:-k:smt102:smt119

The objective gives its marked mag on a 200mm tube lens, focused at infinity. It's a bit of an approximation, but if you use the tube lens at say 150mm from the sensor, you get magnification 0.75x what you would have got. Even if the maths is precise, the measurement isn't, unless you know exactly which point to use.

Chris R

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kaleun96 wrote:Really appreciate all the testing you do Robert. Coming across your website a few months ago first got me on this addictive train ride that is >2x macro photography!

I'm having a little trouble understanding how you calculate effective focal length in these tests. I tried searching the forum and google but without much success.

If I pick up a lens that is not labeled and I would like to know the focal length of the lens, I use a simple formula.

I take the lens, add extension so I can close focus, measure the magnification, than add some extension, lets say 28mm, and measure again.

FL = Added Extension / ( New Magnification - Old Magnification )

FL = +28 / ( 1.62 - 1.21 )

FL = 68mm

Most of what was on Google related to the difference between front/back focal lengths as calculated from the front/back of the lens element, whereas effective focal length was calculated from the middle...or something along those lines. Though it doesn't seem to me that this definition relates to what we're talking about here, where we're reducing the tube length from the ~160mm (+flange depth) to the 144mm in the tests.

For example I can't work out how the focal length of the DCR-150 then changes from 208mm to 178mm (effective). Any pointers would be greatly appreciated!

In the tube lens test I was only interested in the effective FL, that is how it effects the magnification. This was done by measuring the magnification twice. First with the system tube lens FL, and again with the shorter FL tube lens, this could be the same lens with short focus.

With this info you can use this formula.

New effective TL focal length = system tube lens focal length * ( New Magnification / Old Magnification )

Give it a try.

Robert

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Thanks for the info. So there's no way to determine effective focal length before knowing the magnification? I think that's where I was getting confused.

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Hello Robert,

Have I interpreted correctly, that the Raynox DCR-150 performs better at 144mm then 208mm (for the crop-cameras as A6300)?

If yes, have you already detected the optimal position of the Raynox for the best quality (CA, etc)?

So, I have already started to collect the values for the DCR 150/250 and Mittys :-)

https://www.photomacrography.net/forum/ ... highlight=

BR, ADi

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kaleun96 wrote:Thanks for the info. So there's no way to determine effective focal length before knowing the magnification? I think that's where I was getting confused.

Not that I know of.

For what I am doing the results are always more important than the specifications.

Robert

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Adalbert wrote:Hello Robert,

Have I interpreted correctly, that the Raynox DCR-150 performs better at 144mm then 208mm (for the crop-cameras as A6300)?

Hi ADi,

Well I like to think so but when I downsize the infinity focus image or upsize the short focus image to match the other and compare the difference the advantage seems to be less but they do seem to look better to my eyes.

If yes, have you already detected the optimal position of the Raynox for the best quality (CA, etc)?

For the 10X?

No I have not tried the Raynox yet on the 10x yet. The performance of ITL200 in reverse seems like it will be very hard to beat.

Best,

Robert

Last edited by RobertOToole on Wed Oct 24, 2018 11:59 am, edited 1 time in total.

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Hi Robert,

Your test: https://www.closeuphotography.com/tube-lens-test under: “Tube Lenses shorter than 200mm”

Thorlabs ITL200

https://www.closeuphotography.com/thorlabs-itl200/

Set-up:

• Short focus, 144 mm extension from sensor to lens

• Reverse mount

• 75mm from tube lens to objective

Image Quality:

• Overall: 9.6 out of 10

• Center: 8.5

• Corner: 8.5

• Chromatic Aberration Control: 10

.

.

.

RAYNOX 208MM (43mm x 0.50 mount)

Also know as: DCR-150, Macroscopic Lens Model M-150, Model CM-2000 1.5X, +4.8 diopter

Closeuphotography.com/raynox-tube-lens

Set-up:

• Short focus, 144 mm extension from sensor to lens

• Normal mount

• 50mm extenstion from tube lens to objective

Image Quality:

• Overall: 9.6 out of 10

• Center: 9.5

• Corner: 10

• Chromatic Aberration Control: 9.5

So, at 144mm is the quality in the corner for Raynox = 10 and for ITL200 = 8.5.

Independent of the typo at ITL, Raynox has achieved the full 10 points in any case.

The image quality in the corner is very important for me, therefore I’m asking for that :-)

BR, ADi

Last edited by Adalbert on Wed Oct 24, 2018 8:38 am, edited 1 time in total.

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Lou Jost

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Don't forget that you can sometimes get higher corner quality also by increasing the focal length of the the tube lens so that the image circle of good quality gets spread out to the corners. There is a limit to this, as too much expansion gets into empty magnification, as others have pointed out.

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Adalbert

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by Adalbert »

Hello Lou,

Thank you for the hint but I only try to analyse the results of the test of the given configuration.

As far as I can see the DCR-150 performs better at 144mm than 200mm (infinity focus).

Set-up:

• Infinity focus

• Normal mount

• 50mm from tube lens to objective

Image Quality:

• Overall: 8 out of 10

• Center: 8

• Corner: 8

• Chromatic Aberration Control: 9

.

.

Set-up:

• Short focus, 144 mm extension from sensor to lens

• Normal mount

• 50mm extenstion from tube lens to objective

Image Quality:

• Overall: 9.6 out of 10

• Center: 9.5

• Corner: 10

• Chromatic Aberration Control: 9.5

With the A6300 and Mitty 5x, of course.

BTW, normal mount or reverse?

BR, ADi

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Let me add a cautionary note about generalizing Robert's results.

When the rear lens is focused at infinity, the situation is relatively simple. The objective is being used at its design point. Changing the spacing between objective and tube lens will not affect the magnification, and it will not affect aberrations that originate in the objective. Slight misalignment between the objective and tube lens will have no significant effect on the image. Really the only effect of changing the spacing or alignment of the objective and tube lens is to change aberrations that originate in the tube lens, due to changing the distance from axis where pencils of light enter the tube lens.

When the rear lens is not focused at infinity, the world gets much more complicated. In this case, light rays between the two lenses are not parallel, but instead are converging or diverging. In that configuration, changing the spacing between objective and tube lens will also change magnification. It will also change aberrations that originate in the objective, because the objective is no longer being used at its design point. Misalignment between objective and tube lens becomes a much more potent source of new aberrations that originate in the decentering, not really from either lens alone. All of these effects can vary significantly from one objective to another, and some of them become much more important with larger NA objectives. A non-infinity configuration that works great at 5X NA 0.14 can fail miserably at 50X NA 0.55.

--Rik

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Hello Rik,

A non-infinity configuration that works great at 5X NA 0.14 can fail miserably at 50X NA 0.55

Yes, and therefore I would like to collect the optimal values determined empirically a tube-lens, microscope-lens and size of the sensor.

BR, ADi

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Adalbert, yes, it is good to focus on one magnification at a time, but it is also important to realize that there is nothing special about 200mm except that this is the tube focal length that gives the rated magnification. Since you are also already considering other magnifications, I just want to remind you that there are other (possibly better) ways to get sharper corners. Note that using a longer focal length does not take the objective away from its designed optimum, whereas as Rik says, changing the infinity design point can cause problems. Robert has shown that sometimes it works fine, but in cases that haven't been tested, nothing is certain. On the other hand, if the corners are bad and the center is sharp, using a slightly longer focal length is virtually guaranteed to sharpen the corners.

Edit: Of course this will also slightly reduce the overall sharpness; you'll need to experiment to see what balance you want to reach in your application.

Last edited by Lou Jost on Wed Oct 24, 2018 12:05 pm, edited 1 time in total.

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Adalbert wrote:Hi Robert,

Your test: https://www.closeuphotography.com/tube-lens-test under: “Tube Lenses shorter than 200mm”

Thorlabs ITL200

https://www.closeuphotography.com/thorlabs-itl200/

Set-up:

• Short focus, 144 mm extension from sensor to lens

• Reverse mount

• 75mm from tube lens to objective

Image Quality:

• Overall: 9.6 out of 10

• Center: 8.5

• Corner: 8.5

• Chromatic Aberration Control: 10

.

.

.

RAYNOX 208MM (43mm x 0.50 mount)

Also know as: DCR-150, Macroscopic Lens Model M-150, Model CM-2000 1.5X, +4.8 diopter

Closeuphotography.com/raynox-tube-lens

Set-up:

• Short focus, 144 mm extension from sensor to lens

• Normal mount

• 50mm extenstion from tube lens to objective

Image Quality:

• Overall: 9.6 out of 10

• Center: 9.5

• Corner: 10

• Chromatic Aberration Control: 9.5

So, at 144mm is the quality in the corner for Raynox = 10 and for ITL200 = 8.5.

Independent of the typo at ITL, Raynox has achieved the full 10 points in any case.

The image quality in the corner is very important for me, therefore I’m asking for that :-)

BR, ADi

Yes, you are correct.

I don't know how Raynox did those designs. As closeup filters they are ok but as a tube lens they are just about impossible to beat in IQ.

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Also in my recent post about my findings with the Mitutoyo 10x M Plan,

http://www.photomacrography.net/forum/v ... hp?t=38289

Short focus did not improve image quality with the ITL200 but thankfully with infinity and in reverse mount the ITL200 performance was excellent.

FYI, I'm finishing up the 10x test now over the next couple of days. The results are very interesting so far

:o

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Hi Robert,

I’ m looking forward to seeing the results of your test (and comparing them with my assumption)!

So, if I had to guess I would say for the TL focused to the infinity first the ITL200,

then the DCR-150 and for the shorter length of the tube the both on the same place :-)

DCR-150 is really not bad and a good and cheap alternative to the ITL200.

I’m reassembling my Harley rail.

BR, ADi

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Great test Robert, thank you for doing that

Sorry for digging up, but i just now started to think about making univerasal tube lens system (no bellows) and sticking to ~100mm tube would make it really eazy for me.

Could this phenomenon that Robert discovered be explained by this:

1) Tube lens like Raynox is heavily stopped down by microscope objective. So it's not responding to extension change as much as to be expected.

2) Shorter tube lenses are less stopped down, so they do not respond to this "short focusing" as well as longer ones.

3) Since path between objective and lens is no longer 00 , changing distance between objective and lens serves as spherical abberation compensation. And could possibly serve to introduce "cover glass" correction.

4) Perceived improvement is result of larger effective aperture?

5) This result is possible due to moderate objective aperture and will not carry to higher NA objectives, and will eventually bring worse results, unless distance between tube lens and objective will be "nailed". Eventually (with increasing NA and decreasing extension) that "nailed" spot will be inside the tube lens or past it.

Sadly, due to 3,4,5 this is not a good solution for a system with multiple objectives and single tube lens?

Offtopic:

Anyone tested Raynox 250 +1.7 TC vs Raynox 150? Robert :D ?

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Hey Robert

May I ask u which extensions u use for the raynox 150 setup? For both settings

This should also work fine with a full frame camera?

Will use a sony A7R4

Thanks for your help

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I've founmd in my tube lens tests that best full frame settings are not generally the same as best APS settings, and that was true of the Raynox. The arrangement that gave the best central sharpness also gave worse FF corners. That arrangement would look like the best arrangement on APS, but on FF it was worthwhile to sacrifice a bit of central sharpness to get decent corners.

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Lou Jost wrote:I've founmd in my tube lens tests that best full frame settings are not generally the same as best APS settings, and that was true of the Raynox. The arrangement that gave the best central sharpness also gave worse FF corners. That arrangement would look like the best arrangement on APS, but on FF it was worthwhile to sacrifice a bit of central sharpness to get decent corners.

You‘re right Lou

The more I‘m doing my research for the best system to use the mitus on FF the more I get confused ... Dozens of ways to mount and tweak every combination of tubes extensions ...

I will go for the 200mm/180mm camera lens and in front the mitu

And the bellows raynox 150/250 system - think the bellow is quite useful in stepping down the magnification and otherwise I can also revers the raynox lenses to step down...

This forum is really useful but can make u crazy in the next second :D

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Just saw a post about "short focus" with infinite objectives over Facebook, I also watched a video on Youtube about this "technique", I had reservations back then but I liked the result, now since it is being spread over to Facebook and Youtube, it is kinda important. To me, "short focus" is deviating from the very fundamental design, ie, the tube lens should be focused to infinity.

So, does this "short focus" technique have any theoretical backings at all? Or is it a hit and miss, trial and error thing? I can see people will claim something due to some particular settings and this kind of thing can get widely spread out and become a "I heard this on the internet" thing.

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Basically, what I am saying is that, if this does not have any theoretical backings, I am worried that people over Facebook or Youtube might overly GENERALIZE this idea and spent a lot of effort just to "oh, this configuration is even better".

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Regarding theoretical backings, several thoughts come to mind.

1. Any objective is just a lens that happens to be optimized for use as listed on the label. That does not mean it will not work well for other purposes also, particularly if "working well" is defined by flexible criteria.

2. Any lens will continue to work pretty well in some region around its design point. The size of that region depends on aspects that are impossible to predict precisely.

3. In general, the more specialized the lens -- think high magnification and large NA -- the less well it will tolerate deviations from design point. 4X NA 0.1 is very tolerant of being used in "off label" ways, but 50X NA 0.55 is not.

4. Using a lens very far off label is like playing the lottery or mining for gold: most of the time it's not good for much besides amusement, but sometimes you get lucky. In either case there is value, for some people more than others.

That last bit of theory is mostly psychology, not optics, but it's important anyway. If somebody wants to spend time making good pictures, the efficient approach is to stay with known good setups. But if somebody wants to spend time testing other setups to see if they can get lucky, that's OK too. My best advice is to be aware of that difference and act accordingly.

--Rik

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One factor is that microscope objectives are not really optimized for the absolute best image because there are other concerns. These objectives will be used on a nosepiece with a common tube lens, so the setup has to work well with every one of their objectives, and the tube lens has to be focused to infinity to allow room for coaxial illumination, filters and so forth. So it kind of makes sense that at times moving outside the parameters, particularly at lower NAs where spherical aberrations are less fatal, could give you a bump in performance.

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To Rik's advice, maybe I would add that there is nothing special about any particular tube length anyway (except as a way to specify a nominal magnification), so I am not sure it is fair to say that the objective is being used away from its design point.

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Addressing Lou's point, I agree that an infinite objective that is simply used with a shorter tube lens does remain at its design point.

However, my understanding of the "short focus" technique that mjkzz mentions is that the rear lens is not focused at infinity. That does drag the objective away from its design point. Even so, the objective may continue to perform well. For example Robert OToole's tests on his website note that for the Mitutoyo 5X + Raynox DCR-150, "Short focus (less extension) results in less magnification, better sharpness and less CAs".

A good case can be made that the Raynox DCR-150 as tube lens in forward orientation is always being used away from its design point, and certainly using the Raynox+Mitutoyo 5X combo with less than infinity extension also moves the Mitutoyo away from that objective's design point.

Yet in this case two "wrongs" fortuitously add up to one "right", leading to Robert's conclusion and making this particular combo a "known good" setup.

But even if the rear lens remains at infinity focus, you have to ask whether that lens is being used away from its design point. The answer to that question has to be "yes, away from the design point", except for purpose-made tube lenses like the ones from Nikon, Mitutoyo, and Thorlabs. The reason is aperture placement. Lenses that have an internal aperture are designed for that to be the limiting aperture, and when used with an objective out front, that is not the case. The effect is that, away from image center, the image formed by the rear lens is using different portions of the rear lens glass then the lens was optimized for. In particular, lenses with internal apertures are designed around the fact that light from the right side of the field will enter primarily the right side of the lens, but when used with an objective, light from the right side of the field primarily enters the left side of the lens. In mjkzz's other thread, using a 50mm f/1.4 rear lens, those degraded portions of the image near the vignette are formed by a narrow pencil of light that came through the f/1.4 edge of the lens. When used as designed, those portions of the rear lens would never be used at all except when the lens was set at f/1.4, in which case their aberrations would be heavily diluted by other light coming through better behaving parts of the glass, and even so you would not expect the final image to be particularly sharp.

Back to my numbered list, I think the Raynox as tube lens demonstrates at least three of those points very well: it's being used off-label, but works well anyway, despite that it's cheap and easily available as a new manufacture part. This is exactly the sort of situation that I am happy to promote as a "known good" setup for use with infinity focus. Modifying it to be short focus -- less than infinity -- that part I'm not so happy to recommend because it depends heavily on which objective we're talking about. What works well for NA 0.14 may work not nearly so well at NA 0.55, where the increase in spherical aberration is 238 times more important. (SA scales as the 4th power of NA.) Still, I doubt that most of the folks on Facebook will be dealing with such picky objectives, and I'd hope that the ones who do will also be knowledgeable enough to recognize when the edge of the envelope has been pushed too far.

--Rik

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rjlittlefield wrote: ↑

Sat Dec 18, 2021 12:15 pm

Regarding theoretical backings, several thoughts come to mind.

1. Any objective is just a lens that happens to be optimized for use as listed on the label. That does not mean it will not work well for other purposes also, particularly if "working well" is defined by flexible criteria.

2. Any lens will continue to work pretty well in some region around its design point. The size of that region depends on aspects that are impossible to predict precisely.

3. In general, the more specialized the lens -- think high magnification and large NA -- the less well it will tolerate deviations from design point. 4X NA 0.1 is very tolerant of being used in "off label" ways, but 50X NA 0.55 is not.

4. Using a lens very far off label is like playing the lottery or mining for gold: most of the time it's not good for much besides amusement, but sometimes you get lucky. In either case there is value, for some people more than others.

That last bit of theory is mostly psychology, not optics, but it's important anyway. If somebody wants to spend time making good pictures, the efficient approach is to stay with known good setups. But if somebody wants to spend time testing other setups to see if they can get lucky, that's OK too. My best advice is to be aware of that difference and act accordingly.

--Rik

Agree with all.

But one more point, every time I put my Canon 100mm f/2.8 with an objective on it, the camera will set focus to nearest because my adapter has electronic contacts, and sometimes, I forget to focus it to infinity, yet all seem to work without noticeable degradation (to me), it means any objective is just pieces of glasses bending light. And the point is this happens without being lucky! It just works all the time.

However, a big however, I am pretty sure an infinite objective is designed/optimized for being infinite objective, optical engineers spend a lot of effort to get it right. So an infinite objective are not just a group of glasses bending light, they are group of glasses bending light in certain way, it has certain intrinsic properties. But because of it is an infinite objective, a particular type of objective having certain properties, theory says you can push around the focal length of tube lens but keep focused to infinity, to some degree to fit our "hacking" needs (for rich men/women, they design their own objectives to fit their needs)

Rik's #3 is probably a good example of such -- when things get so specialized and optimized, those pieces of glasses are arranged in such way that deviation from their design point will be problematic. And my other thread about pushing a 10x 0.28NA down to 2.5x experiment shows this: the out of focus area has a lot of swirly patterns, definitely not the same if setup normally -- there is a limit. And yes, those out of focus area look like some cheap 4x objectives I got on Taobao

:D

Pushing around a system without respecting its design constrains is like shooting in the dark, like Rik's #4 and when it is becoming a "thing" on the internet . . . I am worried

:D

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rjlittlefield wrote: ↑

Sat Dec 18, 2021 4:59 pm

Addressing Lou's point, I agree that an infinite objective that is simply used with a shorter tube lens does remain at its design point.

However, my understanding of the "short focus" technique that mjkzz mentions is that the rear lens is not focused at infinity. That does drag the objective away from its design point. Even so, the objective may continue to perform well. For example Robert OToole's tests on his website note that for the Mitutoyo 5X + Raynox DCR-150, "Short focus (less extension) results in less magnification, better sharpness and less CAs".

A good case can be made that the Raynox DCR-150 as tube lens in forward orientation is always being used away from its design point, and certainly using the Raynox+Mitutoyo 5X combo with less than infinity extension also moves the Mitutoyo away from that objective's design point.

Yet in this case two "wrongs" fortuitously add up to one "right", leading to Robert's conclusion and making this particular combo a "known good" setup.

But even if the rear lens remains at infinity focus, you have to ask whether that lens is being used away from its design point. The answer to that question has to be "yes, away from the design point", except for purpose-made tube lenses like the ones from Nikon, Mitutoyo, and Thorlabs. The reason is aperture placement. Lenses that have an internal aperture are designed for that to be the limiting aperture, and when used with an objective out front, that is not the case. The effect is that, away from image center, the image formed by the rear lens is using different portions of the rear lens glass then the lens was optimized for. In particular, lenses with internal apertures are designed around the fact that light from the right side of the field will enter primarily the right side of the lens, but when used with an objective, light from the right side of the field primarily enters the left side of the lens. In mjkzz's other thread, using a 50mm f/1.4 rear lens, those degraded portions of the image near the vignette are formed by a narrow pencil of light that came through the f/1.4 edge of the lens. When used as designed, those portions of the rear lens would never be used at all except when the lens was set at f/1.4, in which case their aberrations would be heavily diluted by other light coming through better behaving parts of the glass, and even so you would not expect the final image to be particularly sharp.

Back to my numbered list, I think the Raynox as tube lens demonstrates at least three of those points very well: it's being used off-label, but works well anyway, despite that it's cheap and easily available as a new manufacture part. This is exactly the sort of situation that I am happy to promote as a "known good" setup for use with infinity focus. Modifying it to be short focus -- less than infinity -- that part I'm not so happy to recommend because it depends heavily on which objective we're talking about. What works well for NA 0.14 may work not nearly so well at NA 0.55, where the increase in spherical aberration is 238 times more important. (SA scales as the 4th power of NA.) Still, I doubt that most of the folks on Facebook will be dealing with such picky objectives, and I'd hope that the ones who do will also be knowledgeable enough to recognize when the edge of the envelope has been pushed too far.

--Rik

Oh wow, while I was posting my last one . . . yes, the other thread was the purpose of my point. I am just worried about "short focus" being a "thing" on the internet and I get asked all sort of questions in private that are so out of engineering sense, I some times just ignore them and people are not happy :D

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People should also try ditching the tube lens. At lower magnification, you'd be surprised at how well some objectives behave, even (usually) better central sharpness.

It's all trial an error, what works for one setup isn't indicative of another. You get winners like the Lomo 3,7x and a list of ones that just won't work well. Minolta's 5400 scanner lens comes to mind.

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You get winners like the Lomo 3,7x and a list of ones that just won't work well. Minolta's 5400 scanner lens comes to mind.

Yes, but those examples are the opposite of what you suggest. Finite lenses, one of which does better with a tube lens. Are you sure there are infinity-corrected objectives that do better without a tube lens than with one?

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Lou Jost wrote: ↑

Sun Dec 19, 2021 3:08 pm

You get winners like the Lomo 3,7x and a list of ones that just won't work well. Minolta's 5400 scanner lens comes to mind.

Yes, but those examples are the opposite of what you suggest. Finite lenses, one of which does better with a tube lens. Are you sure there are infinity-corrected objectives that do better without a tube lens than with one?

Yes, if you only look at the centre (corners are pretty poor). Considering many use smallish sensors, this may be preferable.

Give it a go. Try the Mit 10x and 5x for starters.

My example was an objective being used in a non-standard configuration making it perform better, the Minolta 5400 was an example where this didn't apply, that's it. Out of many weird ones I've tried when I still had the 120mm Schneider, Lomo 3,7x was the only one that worked fairly well. I tried one or two other Lomo objectives, I don't remember which because the result wasn't notable.

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Macro_Cosmos wrote: ↑

Sun Dec 19, 2021 7:07 pm

Give it a go. Try the Mit 10x and 5x for starters.

Does this mean that you've tried the Mitutoyo 10X and 5X as finite (no tube lens), and observed that their centers perform better when used that way?

That would be a surprising result for a couple of reasons, so if you have run the tests then it would be great to see the images.

--Rik

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rjlittlefield wrote: ↑

Sun Dec 19, 2021 9:47 pm

Macro_Cosmos wrote: ↑

Sun Dec 19, 2021 7:07 pm

Give it a go. Try the Mit 10x and 5x for starters.

Does this mean that you've tried the Mitutoyo 10X and 5X as finite (no tube lens), and observed that their centers perform better when used that way?

That would be a surprising result for a couple of reasons, so if you have run the tests then it would be great to see the images.

--Rik

Unfortunately I lost all the photos and no longer own either objective. It was quite surprising.

Personally, I cannot recommend doing this because I need to add components in the optical train such as polarisers and beam splitters, doing so will throw spherical aberration off the charts.

I can replicate the test with my Edmund Optics objectives. Unfortunately again, I don't have a 10x anymore. I still have access to the 2x, 5x and 20x.

Since the Christmas holidays are coming, I could try to tick off some of my long delayed comparisons I've loosely promised over the years, but it's usually 35 degrees Celsius or 95 Freedom units. I need a portable AC.

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Macro_Cosmos wrote: ↑

Mon Dec 20, 2021 5:57 pm

Unfortunately I lost all the photos and no longer own either objective. It was quite surprising.

Thanks for the clarification.

One of the general issues that I confront a lot is the idea that "Whatever somebody tells you is probably true. But what exactly are they saying, and what is it true about?"

A few posts above, I wrote

particularly if "working well" is defined by flexible criteria.

Regarding a statement that 10X and 5X Mitutoyo's work better without tube lenses, I see three major possibilities:

(1) Mitutoyo monstrously messed up their optical design and manufacturing processes,

(2) the tester got hold of an unusual sample that did not fit Mitutoyo's intent, or

(3) "better" means something different from sharpest image on subject.

I believe that (3) provides most of the reason when Robert says that short extension improves the image quality. When you use an objective on short extension, you reduce the magnification. Unless the change introduces some pretty severe aberrations, that reduction in magnification probably increases the image sharpness on sensor even though the resolution on subject is likely not as good. I would not be surprised of some similar sort of tradeoff was involved in whatever comparisons you are remembering.

--Rik

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rjlittlefield wrote: ↑

Mon Dec 20, 2021 7:16 pm

One of the general issues that I confront a lot is the idea that "Whatever somebody tells you is probably true. But what exactly are they saying, and what is it true about?"

A few posts above, I wrote

particularly if "working well" is defined by flexible criteria.

Regarding a statement that 10X and 5X Mitutoyo's work better without tube lenses, I see three major possibilities:

(1) Mitutoyo monstrously messed up their optical design and manufacturing processes,

(2) the tester got hold of an unusual sample that did not fit Mitutoyo's intent, or

(3) "better" means something different from sharpest image on subject.

I believe that (3) provides most of the reason when Robert says that short extension improves the image quality. When you use an objective on short extension, you reduce the magnification. Unless the change introduces some pretty severe aberrations, that reduction in magnification probably increases the image sharpness on sensor even though the resolution on subject is likely not as good. I would not be surprised of some similar sort of tradeoff was involved in whatever comparisons you are remembering.

--Rik

Good points Rik.

Another confounding issue would be my experience during that time. I was still a lousy intern trying to understand things, so what I interpreted could be totally fallacious or just downright incorrect. I used to think deviating from the manufacturer's labelled tube lenses is detrimental a few years back and a friend confirmed it -- turned out it was because we were talking about Zeiss, and their tube lenses correct for aberrations (eeek). When I asked if it was fine for Olympus, he said "yes" which got me a bit confused. This WASN'T the applicable to Mitutoyo, Mitutoyo themselves would quite happily use longer tube lenses in their measuring microscopes despite the label saying f=100mm (QV-scope). Zeiss was just an "outlier" of sorts.

For taking away the tube lens, I didn't say it works better (it didn't!), but rather the centre was sharper from memory. I no longer use that word of course (sharp... what is that). Then again, I might have done something very stupid back then, it was 2 years ago. Maybe throwing it out as an open question instead of just doing the comparison was a bit cheeky.

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