Tube Lens Test With MITUTOYO 5X M Plan APO

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rjlittlefield
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Post by rjlittlefield »

RobertOToole wrote:Mounting the MT-1 in reverse and set up for infinity focus, 99% of the lateral CAs are gone and the contrast way up.

I ran a full series, there is quite a bit of field curvature, a lot more than even the Raynox 208mm.
That's a very interesting result, potentially valuable to our community.

But since its usefulness depends on being willing to stack, I can easily see why Mitutoyo would only talk about the flat-field configuration.

I've often wondered how much improvement could be made in lens performance if one simply removed flatness of field from the design evaluation criteria, or at least relaxed the requirement to allow some amount of curvature. Recent work in curved sensors suggests that it's quite a bit, but I haven't looked at any of that very closely.

--Rik

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Post by Macro_Cosmos »

I really appreciate the hard work here, I was going to try something similar but really lack time to do so. I was personally disappointed by the performance of the ITL200, I did mount it "correctly" according to Thorlabs website, turns out it's important to sometimes be a rebel. My ITL was excellent in the centre but the corners are abysmal. It also suffered from stray light issues, which was fixed by some internal flocking. It still performed slightly better than the 200mm/4 ais on my antique d810.

https://farm1.staticflickr.com/916/2928 ... 20dd_o.jpg

Going to try reversing it this time!

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Post by RobertOToole »

rjlittlefield wrote:
But since its usefulness depends on being willing to stack, I can easily see why Mitutoyo would only talk about the flat-field configuration.

--Rik
Seems so strange to me that they would build such well corrected objectives only to thrown a CA and sharpness challenged tube lens in their Finescopes?

Will post normal vs reversed MT1 images tomorrow in a new thread.

Robert

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Post by RobertOToole »

Macro_Cosmos wrote:I really appreciate the hard work here, I was going to try something similar but really lack time to do so. I was personally disappointed by the performance of the ITL200, I did mount it "correctly" according to Thorlabs website, turns out it's important to sometimes be a rebel. My ITL was excellent in the centre but the corners are abysmal. It also suffered from stray light issues, which was fixed by some internal flocking. It still performed slightly better than the 200mm/4 ais on my antique d810.

https://farm1.staticflickr.com/916/2928 ... 20dd_o.jpg

Going to try reversing it this time!
Thanks!

I got lucky on the ITL200....and....Two things got me thinking something was not right. I always check for infinity focus and this is what I got with the Thorlabs set up next to the alternative set up I used:

Image

Also they quote the lens as APO for CAs in visible light but the test images were anything but APO corrected.

BTW I do plan to test the ITL200 on my D850 sometime in the near future.

The low contrast flare issue I fixed before I take a single image. I expect it from all lenses. All the manufacturers sell shiny tubes it seems. Schneider Kreuznach's entire industrial V-mount line needs flocking, can you can believe that! The only tubes I find that are flocked from the factory are Canon's excellent old M39 tubes!

Robert

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Post by RobertOToole »

Okay.

Couldn't resist posting one from the MT-1 re-test, will post the rest tomorrow in a new thread.

MT1 in reverse and 165mm from lens to sensor.

A little leap in quality!

Image

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Post by rjlittlefield »

Robert, I'm confused. In the "Normal Mount", I'm seeing a lot of red fringing on one side of the bright areas. That's typical of CA in peripheral regions. But these are labeled "Center crops".

Can you explain what's going on? What causes the asymmetry?

--Rik

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Post by enricosavazzi »

RobertOToole wrote:[...]
The MT-1 is one of 3 visible wavelength tube lenses offered my Mitutoyo. Maybe another tube is more suitable?
[...]
Considering that Mitutoyo apparently does not use these tube lenses in their own microscopes, it is not completely surprising. The FS-60 and FS-70 are normally equipped with zoom tube lenses (200-400 mm FL), and I have not seen these tube lenses sold separately as components. The newer microscopes that use high-NA, HR objectives have even more sophisticated zoom tube lenses.

One general consideration is that multilayer AR coatings are generally optimized for a specified range of wavelengths, and are less effective outside this range. Multilayer AR coatings can be optimized to perform very well in a limited wavelength range, or "well enough" (but not at the same level) in a broader wavelength range. As a rule of thumb, the broader the wavelength range, the poorer the overall AR performance within the range.

As an example, the AR coatings of the Jenoptik 60 mm f/4 APO are optimized for a 350 to 1,000 nm range (roughly, I am quoting from memory), and as a result they end up being significantly less efficient than good AR multicoatings optimized for VIS only (400-700 nm). I seem to remember a quoted 1% reflection rate within the multispectral range for the 60 mm, as opposed to 0.1% for typical VIS-only AR coatings.

This means in practice that the MT-1 is the most likely of these three models to perform well in VIS. The other two have a transmission spectrum extending into the UV and presumably AR coatings matching the transmission spectrum (and a matching price as well), and as a result they should be poorer performers in the VIS range with respect to AR efficiency.
--ES

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Post by Macro_Cosmos »

RobertOToole wrote: I got lucky on the ITL200....and....Two things got me thinking something was not right. I always check for infinity focus and this is what I got with the Thorlabs set up next to the alternative set up I used:

Image

Also they quote the lens as APO for CAs in visible light but the test images were anything but APO corrected.

BTW I do plan to test the ITL200 on my D850 sometime in the near future.

The low contrast flare issue I fixed before I take a single image. I expect it from all lenses. All the manufacturers sell shiny tubes it seems. Schneider Kreuznach's entire industrial V-mount line needs flocking, can you can believe that! The only tubes I find that are flocked from the factory are Canon's excellent old M39 tubes!

Robert
Absolutely, I was confused about this when mounting the lens as well, I have it setup with accordance to the website, however nothing whatsoever is in focus. I had to play with the variable SM2 tubes to get infinity, the results weren't that good either; haloing and corner fuzziness -- you name it.

It's kind of amazing how the tubes being at $50+ a pop lacks any anti-reflective treatment. Old nikon extension tubes have such treatments, even the cheap extension tubes, 58mm type, found on ebay has this sort of coating. I know someone who is able to apply these coatings, might have a visit next year and get my SM2 tubes treated.

Also if anyone is considering the SM2 system, buy a 52mm reverse mounting adapter, it can be screwed in securely for safe mounting.

I highly recommend the BR-2 or BR-2a official nikon 52mm reverse mounting adapters, these are made better than the $93 thorlabs one, the internal is also coated with anti-reflective material. Oh and it's $15-$30 off ebay all day. Pay less for higher quality, who doesn't like that? I wish I knew.

If one wants to mount an f-mount lens to the tubes, get the K3 tube, such as this: https://www.ebay.com/itm/NIKON-K1-K2-K3 ... on+k3.TRS5

They usually come in a set. Don't pay that 114 for the thorlabs version.

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Post by RobertOToole »

rjlittlefield wrote:Robert, I'm confused. In the "Normal Mount", I'm seeing a lot of red fringing on one side of the bright areas. That's typical of CA in peripheral regions. But these are labeled "Center crops".

Can you explain what's going on? What causes the asymmetry?

--Rik
Sure Rik.

Technically the photo title should read "slightly to the left of center"

This image was posted on the first page;

Image

Robert

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Post by rjlittlefield »

RobertOToole wrote:I got lucky on the ITL200....and....Two things got me thinking something was not right. I always check for infinity focus and this is what I got with the Thorlabs set up next to the alternative set up I used:

Image
This is very strange.

I pulled out my own ITL200 lens and checked the numbers that I had written on it based on my own infinity-focus test measurements.

According to that record, my ITL200 focuses at infinity when the back of the lens housing is 149.4 mm from sensor (177.5 mm from the front of the lens housing).

Right now I can't find Thorlabs' spec for the lens. If it's the same as Nikon's as quoted by Edmund Optics, the numbers will be 151.2 to back of lens barrel, 180.2 to front. That's only a couple of mm different from what I measure.

Regardless of spec, my ITL200 seems clearly much different from Robert's.

--Rik

Edit: to clarify wording.
Last edited by rjlittlefield on Wed Aug 08, 2018 8:24 am, edited 2 times in total.

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Post by RobertOToole »

enricosavazzi wrote:
RobertOToole wrote:[...]
The MT-1 is one of 3 visible wavelength tube lenses offered my Mitutoyo. Maybe another tube is more suitable?
[...]
Considering that Mitutoyo apparently does not use these tube lenses in their own microscopes, it is not completely surprising.
Hi Enrico,

The reason I mentioned that the MT-1 is from a finescope is that the orange Mitutoyo box that the lens arrived in says Code number:970208 MT-1 / FS (finescope).

BTW I have an FS50 finescope (and a QV scope) sitting here partially disassembled and there is a unusual zoom tube inside the FS50 scope head, you are right.

Since Mitutoyo sells the MT-1 (and MT-2) with that 3 bolt mitutoyo mounting flange, they were designed to fit on some type of scope using Mitutoyo objectives that are still APO corrected, but the tube itself is definitely not APO corrected, at least not as well as the ITL200. :D

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Post by RobertOToole »

Macro_Cosmos wrote:
It's kind of amazing how the tubes being at $50+ a pop lacks any anti-reflective treatment. Old nikon extension tubes have such treatments, even the cheap extension tubes, 58mm type, found on ebay has this sort of coating. I know someone who is able to apply these coatings, might have a visit next year and get my SM2 tubes treated.
I'm used to it. I would be surprised if I bought a tube and it was flocked. :D

The SK V-mount industrial gear having shiny internal surfaces? That actually surprised me.

My easy, quick, cheap solution for flare? I buy sheets of black paper that has a soft suede finish. Before I shoot the first image I grab a sheet, roll it up and slide it in the tube. Works perfectly every time. I also have a huge roll of Protostar tape but I use this method a lot more.

This product on Amazon is called; Hygloss Products Black Velour Paper – 8-1/2 x 11 Inches - 10 Pack. $7,21 per 10 pack free shipping.

Image
Macro_Cosmos wrote: Also if anyone is considering the SM2 system, buy a 52mm reverse mounting adapter, it can be screwed in securely for safe mounting.

I highly recommend the BR-2 or BR-2a official nikon 52mm reverse mounting adapters, these are made better than the $93 thorlabs one, the internal is also coated with anti-reflective material. Oh and it's $15-$30 off ebay all day. Pay less for higher quality, who doesn't like that? I wish I knew.
Good tip. Also the Thorlabs mount has male threads. Another thing, this is a really big issue, the Thorlabs unit does not have the F-mount safety stop, a small screw, but they do provide a hole so you can just install your own tiny screw (This keeps the male F-mount from rotating too far in the female side).

Best,

Robert

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Post by RobertOToole »

rjlittlefield wrote:
RobertOToole wrote:I got lucky on the ITL200....and....Two things got me thinking something was not right. I always check for infinity focus and this is what I got with the Thorlabs set up next to the alternative set up I used:

Image
This is very strange.

I pulled out my own ITL200 lens and checked the numbers that I had written on it based on my own infinity-focus test measurements.

According to that record, my ITL200 focuses at infinity when the back of the lens housing is 149.4 mm from sensor (177.5 mm from the front of the lens housing).

Right now I can't find Thorlabs' spec for the lens. If it's the same as Nikon's as quoted by Edmund Optics, the numbers will be 151.2 to back of lens barrel, 180.2 to front. That's only a couple of mm different from what I measure.

Regardless of spec, my ITL200 seems clearly much different from Robert's.

--Rik

Edit: to clarify wording.
Hi Rik,

I also thought it was very strange. I have two ITL200 units. One is from Chris S, the other was sold by an Ebay seller. They look and perform identically, I checked.

I made this diagram for my website, notice that the ITL200 mounting is reversed in the set-up on the right:

Image

Even more unusual, when I followed the info on the Thorlabs site I was seeing 6,7x. When I set the ITL200 using the data on the right, I was just a tiny amount over 5x.

On the Thorlabs site a ITL200 owner observed the same issues as I did apparently but he also received the same response from Thorlabs.

ikky.shura (posted 2014-06-25 19:07:09.623)
Hi, I purchased this ITL200 lens and it seems to me that the front focal length is more like 250mm by trying to image an obect located at > 10x the measured focal lens (assumed to be infinity). I need to know where is the front focal plane for my experiment and since no zemax file is given it's hard to be convinced. Is this lens being tested by Thorlabs? Has anyone else seen this?Thanks,
jlow (posted 2014-07-21 02:29:59.0)
Response from Jeremy at Thorlabs: The effective focal length of the lens is 200mm and its back focal length is 148mm from the mounting side (smaller aperture side). It will probably be better to measure this with sun light instead.

At least someone else has seen something similar to my experiences.

Robert

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Post by RobertOToole »

Sorry Rik I skipped two points..
rjlittlefield wrote: I pulled out my own ITL200 lens and checked the numbers that I had written on it based on my own infinity-focus test measurements.

According to that record, my ITL200 focuses at infinity when the back of the lens housing is 149.4 mm from sensor (177.5 mm from the front of the lens housing).
Thanks for that, but did you do an infinity focus check?
rjlittlefield wrote: Right now I can't find Thorlabs' spec for the lens. If it's the same as Nikon's as quoted by Edmund Optics, the numbers will be 151.2 to back of lens barrel, 180.2 to front. That's only a couple of mm different from what I measure.
I bought an very simlar looking nikon tube lens, MXA20696 on the Nikon box, and it is definitely not the same as the ITL200 externally or internally. Will post something later in a new thread.

Thanks Rik,

Robert

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Post by RobertOToole »

Just FYI:

Note the useful diagram at the bottom.

from: https://www.thorlabs.com/newgrouppage9. ... up_id=5834

Image

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