Tube Lens Test With MITUTOYO 5X M Plan APO

[RobertOToole]

There is a slideshow out there by Kevin P. Thompson and optical design expert called A Brief History of Optical Glasses (particularly wrt Schott) AND Why you care where he talks about what happened in 2002 or so, and why the manufacturers dropped arsenic and lead glass for EU regulation so designers lost 75% of available glass, taking designers back to the 1880s. I don't think anyone could argue that there is some really special glass in that lens that is probably just not available now 20 yrs later.

Found it:

http://www.ora-blogs.com/files/uk10_spi ... tion-2.pdf

[rjlittlefield]

Robert, thanks for the retest on the ITL200.

So now everything looks reasonable -- except of course for the weirdness that the CA is so much less with the lens reversed.

I wonder what tradeoffs drove the Thorlabs design. But short of finding the designer and plying him with goodies, we'll never know!

--Rik

[RobertOToole]

Robert, thanks for the retest on the ITL200.

So now everything looks reasonable -- except of course for the weirdness that the CA is so much less with the lens reversed.

I wonder what tradeoffs drove the Thorlabs design. But short of finding the designer and plying him with goodies, we'll never know!

--Rik

And thanks RIk, for the help figuring out what was going on with the weird magnification numbers.

I didn't examine the slides carefully to look for this but it seems that in reverse the ITL200 field is flat but normal mounting I thought I could see some curvature!

Funny that the Mitutoyo MT-1 acted the same way, maybe 95% of the CAs are gone in reverse. Thats a hard lens to mount though but I found an easy trick I will share when I get time to post something.

Too many projects going at once. I have a used Mitutoyo QV scope sitting in the garage waiting for a teardown. I haven't had a spare minute to touch it. It doesnt help that is 90 degrees here in LA even though I am a mile from the ocean!

[Beatsy]

The most unbelievable thing about that Minolta is how tiny and weightless it is. I used to associate big heavy lenses with quality. The massive 14 element Scanner Nikon, now that was a real lens, one might expect miracles from something like that. But that little Minolta? No way would I have guessed its quality by looking at it.

Similar here! Influenced by fast, high-quality primes, I associate resolution at long working distances with a massive front element (which brings "big heavy" along with it).

The 5400 does bring one "disappointment", in a way. It seems like the quest for the ultimate 2x lens has concluded and there's nothing left to find. Like reaching the last page of a great book. But you never know...

[Macro_Cosmos]

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.

Great tip! I do something similar with some soft telescope flocking adhesive. Instead of sticking it in, I just roll it up and insert it into the tube.

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

Yeah that's another major problem. My adapter got stuck once, scary. What's the parameter of the screw required? I just looked at my $2 cheap adapter and it had the small screw. Maybe I should just salvage one from it. Pretty disappointed with the quality of this expensive adapter.

[ChrisR]

Sorry if this is a repeat but I don't remember reading it. Poking around I found it written clearly in Thorlabs pages, not just the diagram :

Lenses with external SM2 threads are engraved with an arrow next to an infinity symbol ((inf-symbol)) to indicate which side of the lens should face the objective (infinity space), as shown in the diagram above. Item #'s TTL200 and ITL200 should be inserted with the M38 x 0.5 threading facing the objective.

[Davids]

I hope this question doesn't take the thread off topic, if it does I'll gladly start a new thread. It should be an easy one to answer by those more versed in tube lenses than I: is image circle affected by the tube lens or is it dictated by the objective?

[rjlittlefield]

is image circle affected by the tube lens or is it dictated by the objective?

Yes. It can be either, depending on exactly which tube lens and which objective.

For example the Mitutoyo M Plan Apos will cover full frame with high quality image using some tube lenses but not others, while many other objectives will not cover full frame well even using the tube lenses that work with Mitutoyos.

--Rik

[dmillard]

I hope this question doesn't take the thread off topic, if it does I'll gladly start a new thread. It should be an easy one to answer by those more versed in tube lenses than I: is image circle affected by the tube lens or is it dictated by the objective?

From my experience, it's affected by both.

Some lenses used as tube lenses can physically vignette due to their construction. I experienced this with a 150mm Apo Ronar in shutter, that darkened the corners on images taken with a Sony NEX 7, while a similar lens mounted in barrel worked with no problem.

Some objectives project a smaller image circle than others at the same nominal magnification, but using a tube lens with a longer focal length would give a larger image circle, and proportionately greater magnification, at the expense of diminished resolution.

Best regards,
David

[RobertOToole]

Sorry if this is a repeat but I don't remember reading it. Poking around I found it written clearly in Thorlabs pages, not just the diagram :

Lenses with external SM2 threads are engraved with an arrow next to an infinity symbol ((inf-symbol)) to indicate which side of the lens should face the objective (infinity space), as shown in the diagram above. Item #'s TTL200 and ITL200 should be inserted with the M38 x 0.5 threading facing the objective.

Yes, also theSM2A20 ITL200/TTL200 adapter is marked for the recommended mounting direction (which I don't recommend due to CAs) but the male SM2 threading is on both sides so its easy to flip around.

FYI, don't forget that male SM2 parts will thread into M52 x 0.75 (but SM2 female will not accept M52 parts).

BTW, Finally figured out how to do floating in the air exploded diagrams, not that it matters.

[RobertOToole]

Caught a mistake in the retest images but the correct ITL200 images are now up.

The Nikon and Thorlabs lenses look very similar as you can see below but there is a performance difference. Working on a test on the Nikon tube lens now.

L-R, MT-1, Nikon MX!20696, Thorlabs ITL200.

[mjkzz]

wow, nice work. I wish I can get LSA in China.

[rjlittlefield]

When I was teaching math, I used to beat into my students that "Mistakes happen! The important thing is to find them and fix them as soon as possible."

It seems like pretty good advice for the rest of life too.

Nice job catching the mistake!

I will be interested to see a retest on the ITL200.

--Rik

[RobertOToole]

wow, nice work. I wish I can get LSA in China.

Hi Peter, No problem. I have some extras. When I see them cheap I buy one to make sure I have a good copy. Some have Haze. I have a few extras that are clean and clear.

PM me.

[RobertOToole]

When I was teaching math, I used to beat into my students that "Mistakes happen! The important thing is to find them and fix them as soon as possible."

It seems like pretty good advice for the rest of life too.

Nice job catching the mistake!

With the lens being out of sight inside the adapter, I almost missed it.

I will be interested to see a retest on the ITL200.

Deleted the Nikon MXA images and posted the ITL200 re-test images with notes.

Thank again,

Robert