Thorlabs ITL200 as Tube Lens: Initial Impressions (2nd Test)

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Macro_Cosmos
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Thorlabs ITL200 as Tube Lens: Initial Impressions (2nd Test)

Post by Macro_Cosmos »

After that dreaded exam on Measure Theory this morning, I finally have time to work on the SM2 tubes I have just received. I also acquired an ITL200 tube lens from some bankrupt business.

This will be as brief as possible, and the post itself will lack substance since I do not have a comparison to show. I do have one planned. A more detailed post will be made when I get around to doing the comparison. Basically, I want to compare the ITL200 to the Nikon 200mm f/4 ais and Raynox options.

There will be 2 parts to this post.
1. Examination of image quality from the ITL200
2. My impressions on the SM2 tubes and whether they are worth the hassle or not.

These are the SM2 parts I purchased from Thorlabs:
ImageThorlabs SM2 Tubes and ITL-200
The SM2A20 is an overpriced adapter for the ITL200 which takes some odd M38x0.5 threads. There's also another overpriced adapter to mount the SM2 tubes to the F-mount.

The process is briefly outlined as:
1. Build up the tube and focus to infinity. I removed all those retaining rings.
ImageThorlabs ITL-200 Calibration
The long threaded tube allows coarse adjustments, working essentially as a focusing helicoid, obviously the lens will rotate. A ring on the threads allow locking.
2. SM2>M42
3. M42>M26
4. Mitutoyo 10x

This is what the setup looked like:
ImageSetup on Bench
ImageSetup
ImageSetup

Lighting is provided by the OSL2 halogen illuminator from Thorlabs. The weird looking curved contraption is for diffusion. I took apart some clothing hangers and used cable ties on some IKEA rubbery-thing. Diffusion is not perfect by any means. Still have a lot to work on. My setting looks overly complicated because I like to complicate things. A cutting board mounted with arca rails would be as good.

The photographic interest is a wing segment of a sunset moth.

Stackshot set at 5um/step high precision mode. Exposure time was 1.6 seconds I believe. I use Zerene Stacker, Pmax. This is the result with slight post processing (Sharpness +30, clarity +3... the usual adjustments)
Image[url=https://flic.kr/p/28xVd5k]2018-06-27-01.32.15 ZS PMax

Here's the full image:
https://farm2.staticflickr.com/1809/430 ... a22b_o.jpg

Initial findings:
There's obvious stray light getting into the contraption, causing a loss of contrast. There's obvious spots.
Centre of the frame is really good, corners are just so-so. This is fairly consistent with Rik's test: http://www.photomacrography.net/forum/v ... 00&start=0
If you go to the last page, you'll see some problems with my first test and some findings. This caused me to bite the bullet and get some SM2 parts from Thorlabs. SM2 parts are near impossible to find as surplus for some reason, it is all SM1 stuff.

Centre looks really good. The white-paste-like shading is due to stray light entering and bouncing in the tubes -- yuck! Note that I have applied some sharpening and added a bit of clarity. (The semitransparent flakes are dust particles)
Image

This is med-left:
Besides some artefacts caused by inadequate diffusion, it still looks really good. It may look better than the centre to the eye, that part of the frame suffered from stray light.
Image

Here are the 4 corners:
It is certainly alright, but the difference is day and night across the entire frame. There's also some weird spots and what not, which is due to lighting.
Image
Image
Image
Image

My current opinions on the ITL200.
- New one is $400+. Probably not worth it at all. Try find a surplus unit.
- Excellent centre and mid-frame, abysmal corners.
- Entire setup is nice and short (as of now)

My opinions on the SM2 tubes
First, let's look at the prices:
SM2NFM, $93!!!!
Adjustable tubes, 2 of them: $102.51
3 tubes with no external threads: $92.58
2 tube mounts: $60.18
SM2 external coupler with M38x.5 threads: $47.50 :roll:
SM2>M42 ext.>int: $22.95

All this for a stable setup is probably worth it to some people. I personally think the collars offered by MJKZZ to work with the 58mm type ordinary extension tubes would be just as good. Here's my impressions:

- Overpriced, way too expensive for what they offer
- Tube collar only comes in m4/8-32 threads. Why not M6 / 1/4-20''? I guess they wanted it to work with their optical posts. The MJKZZ ones are 1/4 threaded.
- NO ANTI-REFLECTIVE FINISH. This is a major letdown. At over $50 per adjustable tube and $30 per ordinary tube, I'd expect adequate finishes to reduce internal stray light bouncing around, something like graphene coatings or the such. Very bummed by this. If I knew this were the case, I probably wouldn't have bought them, or maybe I'll get SM3 tubes instead, which can be mounted to the camera via a 77mm reverse mounting ring. Just force one in and done. Now I have to apply internal flocking! This is also problematic, since the SM2 tubes I have are threaded internally, which fits over the adjusters. For those segments, I can't physcially stick the flocking material to the internals, this defeats its purpose.
- Overpriced F-mount adapter. $93 for that is ridiculous. Get the Nikon BR2/BR2a 52mm reverse adapter. It does exactly the same thing, just as well. I tried mine and it was a perfect fit. Both are well made, tight fit, and adequate for the task. Save your $93 on anything else. Also the internals of the BR2 is coated to reduce internal reflections. If a $35 new ring can do it, why can't a $93 one do it?
- Very stable, the collars work a charm besides those annoying small threads. Collar also allows easy switching between landscape and portrait shooting, that's always a plus! The locking rings hold the tubes firmly in place, no wobble or play unlike those CCC m42 stuff. But oh, why compare $5 to $50? Almost forgot, both require manual flocking.
- Easy to setup and more versatile than fixed length tubes.

My personal recommendation to anyone who wants to invest in these tubes would be: Think about is carefully. An entry setup would be $250, assuming one uses the BR2/2a from Nikon instead. Seriously, use that $93 on spare tubes instead! For other systems, you're stuck with 52mm reverse adapters. I recommend Nikon users to get a BR2/2a, I've used some $5 cheapos, they are utter scraps.
Also, get the M42 adapter, and purchase M42>? adapters for desired mounting. Thorlab's adapters are high quality but they range from $15-$50+. There's no other option for the M38x0.5 ITL200 that grantees functionality, which is why I bought it.

Here's a list of further tests that need to be done:
- Compare the ITL200 to 200/4ais and Raynox
- Compare the SM2 tubes to conventional extension tubes (and maybe bellows), the ordinary extension tubes are claimed to be coated to reduce reflections. It would be embarrassing if they beat the SM2 tubes on stray light elimination
- Find the sweetspot between the tube and the objective. Thorlabs quotes a 70-170mm mounting distance, mine is at just 65 which is out of the range. The centre is already really good in this case. I honestly don't know how I would go about finding this sweetspot. Do a bunch of stacks? Pull out some chart and look at how aberrations vary at different distances? Any help with this is appreciated. It could lead to some useful information too.

Important note: I did rant extensively on the stray light issue, which perhaps is due to me using the ITL200 outside its specifications. I personally highly doubt this. Putting the SM2 tubes with say Nikon's extension tubes at an angle under a light, it's obvious that the SM2 tubes are "shiny" whilst the Nikon extension tubes does not reflect any light. I'll flock my SM2 tubes and run another test to see if there exist a difference.

Macro_Cosmos
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Post by Macro_Cosmos »

I haven't lost all hope on the SM2 tubes. I'm going to write up a blog post about it and relay the information to thorlabs as an exemplification of the importance of flocking/anti-reflective finishes. Thorlabs imo has the best customer support among photonics and automation companies. I've dealt with Newport and many others, let's just say -- my experience made me a one time customer.

Furthermore, I have a friend in China that has the equipment to apply such anti-reflective finishes. He asked me to bring the tubes to China early next year on my visit. That is perhaps the best solution. I might make an update after this is done. Also obviously I'll show the results to thorlabs.

-- MC

ChrisR
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Post by ChrisR »

I guess this is FX? I found the ITL200 very good on DX. (Which it's designed for!)

Is the inside of the conical adapter well flocked? Horrid things for reflections!

Rafcamera does a 42 to 42 + 52 adapter threaded to take this tube lens, also fits the Nikon whose designation I can't remember - ~MX200?
Here's the adapter - really useful - M42 M F and you can fix a ringlight, 52mm tubes etc to the 52mm.
http://www.photomacrography.net/forum/v ... 128#209128
Chris R

Macro_Cosmos
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Post by Macro_Cosmos »

ChrisR wrote:I guess this is FX? I found the ITL200 very good on DX. (Which it's designed for!)

Is the inside of the conical adapter well flocked? Horrid things for reflections!

Rafcamera does a 42 to 42 + 52 adapter threaded to take this tube lens, also fits the Nikon whose designation I can't remember - ~MX200?
Here's the adapter - really useful - M42 M F and you can fix a ringlight, 52mm tubes etc to the 52mm.
http://www.photomacrography.net/forum/v ... 128#209128
That adapter looks nice, I'll definitely try to get one if I need it. Maybe not now, since I have it set up properly already.

The cone adapter was not flocked. Also I do intend to test it on DX, forgot to add it in the "things to do" section. I heard the MX200 or whatever model from Nikon isn't as good as the raynox tubes.

Only DX I have is a D7100, should be good for the job. I'll give it a go tonight.

Regards,
MC

mawyatt
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Post by mawyatt »

There was a test done here long ago that showed the Raynox 150 (208.3mm) was as good if not better than most dedicated "tube" lenses when used with Mitutoyo objectives. The old Nikon 200mm F4 "Q" has also shown to be a good "tube", as has the Sigma LSA. The Sigma is the best of these three I have and it has 52mm threads.

Also all of these can be had for well under $100 :D

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

Lou Jost
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Post by Lou Jost »

Along with what Mike said, note that the Nikkor Q and similar lenses don't require ANY tubes at all, and only one adapter.

mawyatt
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Post by mawyatt »

Lou,

Certainly as you point out the Nikkor 200mm "Q" is the easiest tube lens of all to use on a Nikon body!! If I'm not trying for the absolute best, this is my "go to" tube lens for the Mittys!!

Think you were the one long ago that pointed me to the "Q" lens (and Vivitar 135), so a very late Thanks!! :smt038

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

Lou Jost
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Post by Lou Jost »

Glad to be helpful, and thank you for your help too!

Macro_Cosmos
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Post by Macro_Cosmos »

Here's what the 200mm ais looks like: Centre top corner bottom.
Image

Image

Centre looks great and corners aren't too bad either.
I tried the ITL200 by flocking the cone adapter. Didn't help at all with the stray light issues at all. I guess the entire tube must be flocked.

Macro_Cosmos
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Post by Macro_Cosmos »

I'd say the itl200 has better resolution in the centre. The 200ais doesn't really fall behind at all. It's almost as good. With better diffusion, it can be improved dramatically.

Still deciding if I should keep the ITL200 or not.

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