Sony A7R with microscope lens

[enricosavazzi]

Metabones seems to no longer produce these adapters (I guess they discovered that they can earn more from "smart" Canon to Sony adapters and speed boosters). However, second-hand Metabones "dumb" adapters can still be found on the second-hand market, sometimes at relatively good prices.

B&H has this in stock ($100) https://www.bhphotovideo.com/c/product/ ... t_nex.html
I'm definitely considering it, though someone said he had issues with it (infinity doesn't line up, doesn't click nicely in place) compared with a K&F Concept $30 adapter they have... so I read about those and some seem fine, but they have some terrible reviews too.
This is why I'm a bit nervous...
[...]

I checked a few reviews, and the concern about flocking fibers coming off is real, especially with a new-bought adapter. This applies only to the latest generation of Metabones adapters. I have a few second-hand older ones that are painted but not flocked, as well as a couple of flocked ones. In total I have perhaps a dozen Metabones adapters, with different attachments (and 2-3 dozen of other brands or no-brand).

To reduce the chance of flocking fibers coming loose, one can lightly brush the flocked surfaces with a flexible brush, then flush out the loose fibers with compressed air. It is also possible to paint the flocked surfaces flat black to glue the fibers in place. One of the negative reviews seems to be from a photographer who expects no dust ever to land on his camera sensor. Dust, like fibers, is a fact of life and can be blown off rather easily, especially larger fibers.

Then there can always be the odd adapter with a bayonet that fits too loosely or too tightly. I do notice slight differences of fit among my Metabones adapters, which probably span a production date of at least a decade. In one case I made a front bayonet tighter by increasing the bend of its blade springs. The rear bayonet can be difficult or impossible to adjust if it is out of specs, although one can check for burs and file them away with a very small file, then wash and brush the adapter with dishwashing detergent to remove all metal dust and let it dry. Rinse in isopropyl alcohol to dry faster. Washing a flocked adapter and/or rinsing it with alcohol may not be recommended if you want to keep the original flocking, I have not done this so far.

[Macro_Cosmos]

You say you can't think of a scenario where a longer tube lens would be useful, but at the same time you note that a 200mm tube lens often gives poor corners on FF. The problem you note about edge quality is exactl ythe scenario that longer focal length tube lenses will fix for you.

As you know, if you are happy with the results of a 200mm tube lens on an APS sensor, you will get the same image, with the same corner quality, by using a 300mm tube lens on a FF sensor. The FF image will be better than the APS image because you are putting more pixels under each feature. Yes, some of this will be empty magnification, so the improvement won't be linear with the increase in pixels per feature, but as Rik and others have shown, there are still advantages to having more pixels.

It is a misunderstanding to think there is anything special about a 200mm tube lens, independent of sensor size. The size of the sensor matters. A 500mm-600mm tube lens would be appropriate for medium format. For FF, the natural focal length for a tube lens would be 300mm (given the experience of most of our community that a 200mm tube lens is a good fit to an APS sensor).

Sure, some objectives will not be able to take much advantage of the extra pixels under each object feature, but some will. The 20x 0.75 apo Nikon is an example. There are 10x 0.45 and even 10x 0.50 objectives.

The 200mm ITL200/CMH-200 yields poor corners on FF because it's not designed for FF, it's a crop sensor lens. I didn't say 200mm will often give poor results, I said the ITL200 will always give poor results because it's a crop sensor lens. I had the opportunity to test a fullframe optimised tube lens and it's better in every aspect, corners or centre. It would have been available if some kind of malware didn't hit the world.

In theory, a longer tube lens cuts out the nasty corners, that's based on a huge assumption. Assuming the 300mm TL performs the same or better than the 200mm counterpart. This is often not the case, from personal experience of course. More pixels is always theoretically better too, but in practice, it kind of doesn't matter. The competition is tough here, we have the ITL200 and the clone CMH-200 that's a tad better. Which 300mm lens out there can outperform this couple? Moreover, is spending at least $250 to try out say, a 300mm ai-s truly worth it when one can simply make a small panorama? Sure it will take more time... still less than trying out a myriad of different 300mm lenses to find one or two gems (which I respect).

An objective that couples well with a 12MP FF monochrome sensor will work nicely on a 24-36MP colour sensor, and yield more information on a 50MP colour sensor. This is always true, more pixels more information; however the amount you'll get depends on the NA and other aspects. A 10x NA0.28 will benefit from that 50MP, you'll get a load more information. A 20x NA0.42 however won't. In theory, there's more stuff; in practice, you'll see minimal improvements. This is something I think we agree on. A 20x at an astounding NA of 0.75 couples with a monochrome sensor of 64 whopping MPs, it should in theory blow a 100MP FF coloured sensor out of existence. If we pull this to 40x via a 400mm TL, it drops to 15MP which is still really good.

The drop follows a nice cubic function.

An objective like that is only good for transillumination/coaxial epi due to the WD, which I'm guessing is around 0.5mm... oh it's typically coverslip corrected too. Higher NA brings stacking errors or something, I've never studied this. Only recently I've been encountering such problems. A sunset moth stack turned the lines in the scales into little zig zags.

Due to the extremely short WD, nothing but coaxial epi works for reflected light.

All my experience points to one thing, always follow the manufacturer's specifications. Outside of that, it's unexplored territory. I used to use an ITL200 on my Olympus microscope. While it's true that the 20mm difference is minute on paper, I get weird distortions. I thought this was just the objectives being silly, mounting the U-TLU (180mm) showed otherwise. A 200mm TL, or 180mm, 165mm in the case of Zeiss for the matter is special, it's recommended by the manufacture, the engineers design the lenses to fit these FLs.

The same is true with the 2.5x HR and 5x NA0.28 (also HR) QV-objectives, which to manufacturer's spec, works on a 100mm TL. With a 200mm TL, the results are astounding. The former beats any 5x I have due to the exceptionally high NA, the latter is "almost" as good as a native 10x Mplan Apo. How about the corners though? Well, they aren't the best, the 2.5x HR outperforms my 5x objectives but comes with a lot of distortion; the 5x pushed to 10x is nearly indistinguishable to my native 10x. Of course, if one doesn't care about distortion, it's totally fine.

Longer telephotos have other problems beyond this. For example, Nikon's 200-400mm VR2 version is simply horrendous at infinity. At closer focus, it's very sharp. The newer 180-400mm fixed it to some extent. I can't speak for other telephoto lenses. The 300mms I've used are the F4.5 ai-s, F4 AF-s D version and F2.8 ai-s. Good close-focus results, but not so good at infinity. I guess those non-macro large format lenses will do a lot better as manufactures probably account for infinity focus. But then, the Schneider apo-digitar 120mm M version (M for macro) does better at infinity than the non-M version! See where I'm getting to... unexplored...
If I was tasked with designing a 300mm or 400mm telephoto for FF cameras, I'll have close-mid focus in mind; because when I think of those FLs, I think of wildlife, sports, and portraits for those defocus crazed photogs, landscapes ie infinity comes last. If it's a 100-400 kind of lens, then I'll seek a balance between close-mid-infinity, as such a lens is designed to be versatile, not a specialised optic.

I'm still waiting to see someone test their 100-400mm Canon RF mount or Sony E mount. These lenses are said to be very good at the entire range. Now Sigma offers a slightly slower, but cheaper 100-400mm as well. All this time though, I don't see the keen explorer. Nikon's S-line will be out by next year, but spending nearly $4000 AUD to buy a lens to try out objectives is simply out of the question. Loaning is also not an option, one might as well buy a new copy and then sell it. Typical loaner prices here are $80 a day with seven days minimum!

It's totally fine to explore these things. I'm in the middle of finding a good 100-120mm TL, tested several so far with sad results. The Gretag just flew in and I'm getting an adaptor made soon. I will however not recommend outside of the manufacture's spec sheet, especially when it comes to beginners, until there's sufficient information. For instance the raynox, it wasn't "designed" to be used as a TL, but there's plentiful information and tests to show how well it does, and mounting is trivial at this point; I would not have recommended the raynox 4 years ago.

[Macro_Cosmos]

I checked a few reviews, and the concern about flocking fibers coming off is real, especially with a new-bought adapter. This applies only to the latest generation of Metabones adapters. I have a few second-hand older ones that are painted but not flocked, as well as a couple of flocked ones. In total I have perhaps a dozen Metabones adapters, with different attachments (and 2-3 dozen of other brands or no-brand).

Wow that looks nasty. I suppose that's where unflocked tubes can be better. I'd take unflocked over sketchy paint/flocking deposit.
Same remains for flocking adhesives though. They have a lot of tiny fibres.
Just get one of these tape roller things from a dollar store, they are designed to remove dust, hair, and those cotton-ball things from clothing.

Give the flocking adhesive a good rollin' before application.

[Lou Jost]

I get the feeling we don't disagree as much as may appear. You agree that high-NA objectives like the ones I mentioned would give excellent results with a 400mm lens. You also note that the QV objectives are excellent on a tube lens that is twice the focal length of the TL quoted for those objectives. I don't know what went wrong with the Olympus objective with 180mm vs 200mm TL but I am sure (from my own experience) that this has to do with the special characteristics of the ITL200-type TL. Oly objectves are excellent when used with most 200mm and 400mm tube lenses. Many on this forum also have truly excellent results with tube lenses much shorter than 200mm. All of this indicates that there is nothing special about 200mm.

"All my experience points to one thing, always follow the manufacturer's specifications. Outside of that, it's unexplored territory."

While I agree with that in general, in this case I think the 200mm spec is just the reference focal length that gives the magnification printed on the objective.

I think the valid assertions in your response are those regarding our knowledge of good tube lenses. We do know some great 200mm tube lenses, so I agree that this is a safe bet for APS. However, it's not true that we don't know good tube lenses at other focal lengths. The Raynox 125mm lens is known excellent if the objective has a big enough image circle or if the sensor is small. Beatsy and I have both posted good results with other short tube lenses. Many people on this forum have also shown excellent results with longer-than-200mm tube lenses.

[JKT]

The resolution calculation from Macro_Cosmos also assumes that the sharp image from the objective always covers the sensor. When it does not with the shorter tube, the final resolution can increase with the longer tube lens. Combine that with low resolution FF sensor and the above-mentioned 20x 0.75 & 10x 0.50 objectives and it should be pretty obvious why I'm still keen to find a cheap 300mm (or a bit over) tube lens. As it happens Canon EF 1.4x Mark II seems to be reasonably sharp, but it also introduces quite a barrel distortion. I've even resorted to trying 52mm Canon 250D, which at first try wasn't half as bad as its reputation. The low resolution sensor may have something to do with that.

[rjlittlefield]

Higher NA brings stacking errors or something, I've never studied this. Only recently I've been encountering such problems. A sunset moth stack turned the lines in the scales into little zig zags.

This looks like a common effect that I've come to describe as "features squirming around laterally as focus is changed". See for example the animation at http://www.photomacrography.net/forum/v ... 87#p149187 .

The effect happens because with shiny subjects, the light that forms the image of each point on the subject mostly enters the lens from one side. The one-sided light causes that the image of that point to move laterally as focus is changed. The lateral movement would be corrected by alignment if all points moved together, but they don't. The angle of the light that forms the image depends on the local orientation of the subject surface at each point, and because that orientation changes, so do the directions and distances of the apparent movement. It is those different directions and distances for different features that cause the "squirming".

The only attack that I know for this problem is to use focus step sizes that are much smaller than normal, so the stacking software has at least some chance of choosing frames in which each feature is almost perfectly focused and therefore appears at almost its correct lateral position. For sunset moth scales, which are very shiny, using a step size that is say 5 times less than nominal DOF can be very helpful.

--Rik

[clarnibass]

Thanks everyone. I was hoping to do this without knowing much about it A hopeless goal maybe...

I just read a few hours (or days... who notices time at this point) on Robert Otoole's website. He has some examples of why Thorlab's suggestion for mounting the ITL200 is wrong and also that with some objectives a shorter than 200mm tube lens can be excellent or even better (than the resized 200mm version), though I guess it might mean it doesn't cover the frame in some cases (depending on objective, sensor and tube lens).

When you order from ThorLabs they put a box of junk food in with the order. It's almost worthwhile to not get the order exactly right, to forget some gimcrack or other, so you have to reorder and get more junk food.

One supplier I used to order from for one of my jobs (unrelated to photography) always put toffee and everyone else (we have a forum too) are always so thrilled... I'm not as much

For the ITL200 and CMH-200 clone, yes they are both designed for crop sensors. This means the edges aren't the best.

I guess the question is... is there a better option (still using the Mitutoto M Plan)?
With the Nikon 200mm lens it's a very simple setup and results are... good. Corners are ok. Not as sharp as the center, but I wouldn't say they are terrible (on a full frame).

Or as I've said, get yourself a good sony to M42 adaptor, some wemacro tubes, and wemacro's ITL200/CMH-200 clone adaptor, which is also M42. Email william about it, it's $25 or something. That setup would cost I'm guessing $200 maximum. All the mounting is the same as above, you're just using M42 instead of the larger SM2.

I'm considering all options. WeMacro, MJKZZ, Thorlabs... others if there are any. I spoke with William about their options but trying to figure out what is actually needed to mount the ITL200 (which is one option I'm considering).

For 2x and 3.6x and the such, you're better off with the Laowa 25mm ultra-macro. It does 2.5x-5x. It has a bit of LoCA and a bit less resolution than the Mit 5x, it wins in every other aspect... and no messing with tubes or adaptors, it comes in the Sony mount.

I think I will get the Laowa 100mm x2 lens, seems to be excellent, even though the diameter at the end is larger than my current setup (by about 10mm), the longer working distance (approx 80mm compared with 35mm now) more than makes up for it. Probably better quality too.
I don't think I'll go with the Laowa 25mm. Barely longer working distance at x5 (40mm compared with 35mm) but much larger diameter. I like the very small diameter for lighting. Also I already have the Mitutoyo and it seems it's better overall. There are other reason too.

Which 300mm lens out there can outperform this couple? Moreover, is spending at least $250 to try out say, a 300mm ai-s truly worth it when one can simply make a small panorama? Sure it will take more time... still less than trying out a myriad of different 300mm lenses to find one or two gems (which I respect).

At least in my case, I'm not really worried about using a longer than 200mm tube lens, maybe, maybe not. The reason I mentioned it in the first place, is because I already have one of those older manual Nikon 400mm lenses and I'd like to keep using it for things completely unrelated to macro

Thanks again

[Macro_Cosmos]

Higher NA brings stacking errors or something, I've never studied this. Only recently I've been encountering such problems. A sunset moth stack turned the lines in the scales into little zig zags.

The only attack that I know for this problem is to use focus step sizes that are much smaller than normal, so the stacking software has at least some chance of choosing frames in which each feature is almost perfectly focused and therefore appears at almost its correct lateral position. For sunset moth scales, which are very shiny, using a step size that is say 5 times less than nominal DOF can be very helpful.

--Rik

Thanks for the in-depth explanation, as usual.
5 times less would be gigantic feat... that image I showcased comes from a 700 [!!!] image stack, it's at 700 only because my 32GB XQD choked out. I can't imagine going 5 times more, even though I can if I really want to.
There's maybe other problems too, I simply taped a (cheap brandless) coverslip over the moth wing. I'm gonna call it a crude and bad method. There's definitely air gaps that will cause various problems.

I just read a few hours (or days... who notices time at this point) on Robert Otoole's website. He has some examples of why Thorlab's suggestion for mounting the ITL200 is wrong and also that with some objectives a shorter than 200mm tube lens can be excellent or even better (than the resized 200mm version), though I guess it might mean it doesn't cover the frame in some cases (depending on objective, sensor and tube lens).

Welp, sorry for hijacking your thread with my walls of text. This "less than standard" TL discussion really should be placed elsewhere.
No, thorlabs' mounting isn't wrong. It's the correct way to mount the tube lens, and people in the industry follow it.
The TL is focused at infinity, the space between the tube lens and the objective is known as the infinity space. That's how an infinity conjugate microscopy system functions. This space allows the insertion of planar optical components with no penalty on aberrations and minimal penalties on resolution. My frankenmeasurescope is built around an ITL200. Reversing it takes this benefit away. While it's fine if you're trying to focus stack photos, it's not if you want to insert anything in the optical path, as doing so will definitely alter the focus and potentially bring in unwanted aberrations. I should run a test some time, been too busy with microscopes and work recently.

The ITL200 does yield better corners when reversed for 5x and 10x. At 20x and above, this is no longer true. I no longer have a 10x objective now that I think about it, oh well.

Using a TL shorter than the manufacture's spec does give you better results than typical normal native objectives. For example, a 10x NA 0.28 shrunk to 5x via a 100mm TL will outperform a 5x Mplan at 0.14 NA. However, the corners will almost definitely be horrifying -- assuming you're on fullframe of course. That's why there are people who use a smaller sensor camera to rid those nasty corners.

There are better options than the ITL200. The Nikon 200mm f/4 ai-s for example has robust image quality, while the centre trails the ITL200, the corners are great. However, there's always the option to make a simple 2-stack panorama, this eliminates the bad ITL200 corners entirely.
Normally, I won't recommend the ITL200. It's nearly $500, offers about 10% better performance (at most) compared to the Raynox, while being 10 times more expensive, while still requiring tubing. It's different now, the clone CMH-200 is cheaper than a mint 200mm ai-s. Wemacro's M42 tubes are great. The adaptor is only $25, doesn't require expensive unflocked thorlabs tubing.

I'm considering all options. WeMacro, MJKZZ, Thorlabs... others if there are any. I spoke with William about their options but trying to figure out what is actually needed to mount the ITL200 (which is one option I'm considering).

You need to ask him specifically for the ITL200 adaptor. The ITL200 has M38x0.5 threads. William's adaptor allows mounting both ways, so you can reverse it if you want to.
In my article, I do show the adaptor next to the Thorlabs one.

I think I will get the Laowa 100mm x2 lens, seems to be excellent, even though the diameter at the end is larger than my current setup (by about 10mm), the longer working distance (approx 80mm compared with 35mm now) more than makes up for it. Probably better quality too.
I don't think I'll go with the Laowa 25mm. Barely longer working distance at x5 (40mm compared with 35mm) but much larger diameter. I like the very small diameter for lighting. Also I already have the Mitutoyo and it seems it's better overall. There are other reason too.

Nope. Longer working distance means greater depth of field, which means smaller numerical aperture and thus less resolution. That's why the Laowa 25mm ultra-macro basically obliterates the Zhongyi 85mm 1-5x which offers mindbogglingly (or rather, unnecessary) long working distances. It's way bigger and more expensive.
40mm is plentiful for any studio setup. IMO, 3mm is "enough", <3mm requires some creative lighting methods. My line is drawn at 2mm for off-axis reflected light.
Laowa's 100mm is still good, it goes to infinity.

Anyhow, there's lots of good choices. Laowa might be releasing even higher mag. lenses, 10x... 20x... Time will tell, no guarantees. They specialise in weird and niche stuff, that's in their motto.

[clarnibass]

Welp, sorry for hijacking your thread with my walls of text. This "less than standard" TL discussion really should be placed elsewhere.

I meant in a good way
When I bought my last lathe, I was already working on lathes for years, but I knew next to nothing about electrical stuff. Long story short... I ended up installing and wiring a VFD by myself... I imagined something similar might happen here...

No, thorlabs' mounting isn't wrong. It's the correct way to mount the tube lens, and people in the industry follow it.

Sorry maybe my terms are wrong and I'm not sure about this. I meant what he shows here https://www.closeuphotography.com/thorlabs-itl200/
Scroll down to the "Important note on setting up the ITL200" and the diagram. He specifically says this is if you want the best image quality, which is what I meant too.

He mentions "a comparison below" but I only see the reversed test there. If I compare with the non-reversed from one of his other pages, the reversed one seems slightly better. The ITL200 also look very visibly better than the Nikon 200mm lens he tested, especially in the corners, but I think those are APSC corners (I can't find that he mentioned what camera was used but the photo looks like an APSC to me?).

There are better options than the ITL200. The Nikon 200mm f/4 ai-s for example has robust image quality, while the centre trails the ITL200, the corners are great. However, there's always the option to make a simple 2-stack panorama, this eliminates the bad ITL200 corners entirely.

That's the lens I have.
By the way part of the reason I want to get a higher MP camera in the first place is to avoid more stacks which takes a huge amount of time
There are other reasons too, though some are unrelated to macro.

Normally, I won't recommend the ITL200. It's nearly $500, offers about 10% better performance (at most) compared to the Raynox, while being 10 times more expensive, while still requiring tubing. It's different now, the clone CMH-200 is cheaper than a mint 200mm ai-s. Wemacro's M42 tubes are great. The adaptor is only $25, doesn't require expensive unflocked thorlabs tubing.

I meant either the ITL200 or the clone, since they are supposedly the same in how you attach them and the way different mounting affects them.

Nope. Longer working distance means greater depth of field, which means smaller numerical aperture and thus less resolution. That's why the Laowa 25mm ultra-macro basically obliterates the Zhongyi 85mm 1-5x which offers mindbogglingly (or rather, unnecessary) long working distances. It's way bigger and more expensive.
40mm is plentiful for any studio setup. IMO, 3mm is "enough", <3mm requires some creative lighting methods. My line is drawn at 2mm for off-axis reflected light.
Laowa's 100mm is still good, it goes to infinity.

Well, I don't like the 35mm WD (maybe it's slightly less, closer to 30mm, not sure) with 62mm diameter lens that I have right now for x2 magnification. From what I could find about the Laowa 100mm, it's at least very good at any magnification, and the extra WD would make lighting easier/better. I would also use it as a regular macro and studio lens. I'm half-guessing it's better than my Nikon 105mm it would replace and my x2 setup.
I don't have a "problem" with 40mm WD at x5, but prefer the much smaller diameter of the objective for lighting and I already have it.

[Macro_Cosmos]

Ah makes more sense. A higher MP won't help that much if your objective's NA isn't large enough, but it's understandable for other stuff and cropping. For Mitutoyo objectives, generally 24-36MP is adequate. The problem with most 24MP fullframe cameras is the existence of an annoying lowpass filter.

Longer WD for larger lenses makes sense, if the WD is short and the front is big, lighting is incredibly difficult. People remove the objective housings just to make short WD objectives easier to light.
Laowa's 100mm is better than Nikon's 105mm VR. Note that Christopher Frost's review features a bad sample of the 105mm VR, but the Laowa is better regardless. Another good 1x lens is the Sigma 70mm art, Robert reviewed that as well.

My point of "thorlabs mounting is wrong" was a response to the article. They aren't wrong, it's just that somehow reversing the ITL200 gave nicer corners. Doesn't mean that it should be reversed as a standard practice. Ehh I'll give myself a week to make my own assessment on the setup. I have several objectives to try out.

[Steve S]

About edge/corner definition: it would be helpful if people reporting on that would always indicate whether the observation was with a single image, typically an IC, or alternatively a stack of images, typically of a three-dimensional object. Edges can be degraded by curvature of field, which is generally suppressed in stacks. I've done a certain amount if testing of the ThorLabs clone of the Mitty, not very controlled or systematic, but I certainly cannot categorically state it performs better reversed. I've done only stacks.

And about the Mitty tube lens. It has quite a bit of pupillary magnification, telephoto if used as designed, retrofocus if reversed. I wonder if the designers of the lens settled on this not as part of "optimizing for APS-C", but for dimensional convenience in designing the beam-splitting (etc) optics between the tube lens and what microscopists rather amusingly call the "intermediate image." It would be helpful if someone who knows microscopes would address this.

Those who, like me, bemoan the limited image circle of the Mitty's should get a load that of the Wild ApoZoom. The Mittys are large format compared to it.

[Lou Jost]

Steve, that's a very important difference you point out between the microscope manufacturers' tube lenses and our home-made ones like the Raynox or ordinary camera lenses. In a microscope, the tube lens has to be far from the objective in order to leave space for the turret assembly, fluorescence cubes, etc. In the home-made case we don't usually care about that. So it is theoretically possible that home-made solutions could have better image qualitry than the dedictaed tube lenses, since they do not have that constraint.On the other hand, I can say from personal experience that the home-made solutions do not work well when placed far from the objective. That's where the purpose-built tube lenses like the ITL200 really shine.

[Macro_Cosmos]

About edge/corner definition: it would be helpful if people reporting on that would always indicate whether the observation was with a single image, typically an IC, or alternatively a stack of images, typically of a three-dimensional object. Edges can be degraded by curvature of field, which is generally suppressed in stacks. I've done a certain amount if testing of the ThorLabs clone of the Mitty, not very controlled or systematic, but I certainly cannot categorically state it performs better reversed. I've done only stacks.

And about the Mitty tube lens. It has quite a bit of pupillary magnification, telephoto if used as designed, retrofocus if reversed. I wonder if the designers of the lens settled on this not as part of "optimizing for APS-C", but for dimensional convenience in designing the beam-splitting (etc) optics between the tube lens and what microscopists rather amusingly call the "intermediate image."

Noted, useful information here. I plan on running the test later.
What do you mean by "Thorlabs clone of the Mitty"? If we're on the same page, I think you meant "Carman Haas clone of the Thorlabs"?

I personally am not being completely scientifically rigorous when I toss around the term "optimised". Optimised DOES NOT mean "designed for", ie an objective can be designed for polarised light, but not necessarily optimised for it (strain-free objectives are optimised for polarised light). Common apochromatic objectives actually perform worse for polarised light microscopy:

Apochromatic objectives from older fixed tube length microscopes should be avoided because it is difficult to remove all residual stress and strain from the numerous lens elements and tight mounts.
https://www.olympus-lifescience.com/en/ ... iguration/

Well yeah, I should know better. I don't have anything to back up the claims that the ITL200 is optimised for APS-C. I personally think it's just fine for FF.

For microscopy, a tube lens must accommodate various planar components being tossed in the infinity space. Fluorescence cubes, beam splitters, colour correction filters, expensive normarski prisms... blah.

On the other hand, I can say from personal experience that the home-made solutions do not work well when placed far from the objective. That's where the purpose-built tube lenses like the ITL200 really shine.

Yep, same here. I've tried my measurescope setup with a 200mm telephoto and the FF-optimised photographic tube lens I have, horrible results, despite theory telling me that I can shove in components as I please when the TL is focused to infinity. My 25mm beamsplitter works fine on an ITL200, worsened corners on FF but it's alright, what I get instead with the 200mm TL/lens is heavy mechanical vignetting and loads of spherical aberration.

Maybe this is why reversing the ITL200 yields better results at 5x and 10x.

[Steve S]

I mistakenly thought Mitutoyo was responsible for the M38-thread-on-one-end design. My bad. I now see it's Nikon and Thorlabs microscopes that have that design.

[rjlittlefield]

On the other hand, I can say from personal experience that the home-made solutions do not work well when placed far from the objective. That's where the purpose-built tube lenses like the ITL200 really shine.

Yep, same here. I've tried my measurescope setup with a 200mm telephoto and the FF-optimised photographic tube lens I have, horrible results, despite theory telling me that I can shove in components as I please when the TL is focused to infinity. My 25mm beamsplitter works fine on an ITL200, worsened corners on FF but it's alright, what I get instead with the 200mm TL/lens is heavy mechanical vignetting and loads of spherical aberration.

Yeah, that part of the theory is too simple. What it overlooks is that with normal telephoto lenses, the built-in aperture selects light from each side of the scene that entered that same side of the lens. But when we stick an objective in front, the objective acts as the aperture, and then the light from each side of the scene enters the opposite side of the lens, in an area that would ordinarily be used only at wide aperture and even then would be only a small part of the light forming the image. No surprise (in retrospect!), this use of the "wrong parts of the glass" can have bad effects.

I have no doubt that the purpose-built tube lenses are designed with those opposite-side ray paths in mind.

--Rik