Thorlabs super apochromat 2x

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Scarodactyl
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Thorlabs super apochromat 2x

Post by Scarodactyl »

I just nabbed one of these on eBay from seller compsell_020100, and he said he has two more to be listed in the next couple days. Head to head to head against my mitutoyo 2x and optem 2.5x to come.
Will the small 22mm field number prove optimistic or pessimistic? Will the suspiciously bad example photo on thorlabs' site end up being accurate, or was their condenser just set up poorly? Is this apo superb or subpar? Tune in next time.
Last edited by Scarodactyl on Mon Jun 27, 2022 12:49 am, edited 3 times in total.

PeteM
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Re: Thorlabs super apochromat 2x

Post by PeteM »

I'll be interested in what you learn.

Lou Jost
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Re: Thorlabs super apochromat 2x

Post by Lou Jost »

Me too, I've always wondered about that one and the 4x. The small field size (and high retail price) has kept me from pulling the trigger so far.

Scarodactyl
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Re: Thorlabs super apochromat 2x

Post by Scarodactyl »

It is a weird line. Why do they have a mismatch of threads and parfocal lengths? Why would you make a 95mm parfocal objective with m25 threads?? Even Nikon's own 95mm objectives have m26 threads. Who makes them??
I see the new listing has a significantly higher price than the last one. Guess the first two sold too fast (someone else got one before me too, maybe another poster here?)
Oh, I see Thorlabs added a 50x HR apo objective to their lineup (not in the SAP line, just as a separate long working distance objective) which resembles the Mitutoyo 50x HR. Neat.

RobertOToole
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Re: Thorlabs super apochromat 2x

Post by RobertOToole »

Scarodactyl wrote:
Tue Jun 21, 2022 8:41 pm
I just nabbed one of these on eBay from seller compsell_020100, and he said he has two more to be listed in the next couple days. Head to head to head against my mitutoyo 2x and optem 2.5x to come.
Will the small 22mm field number prove optimistic or pessimistic? Will the suspiciously bad example photo on thorlabs' site end up being accurate, or was their condenser just set up poorly? Is this apo super or subpar? Tune in next time.
Thorlabs says someplace on their site: "The Field of View will be flat, the TL2X-SAP will be diffraction limited over its full Field of View." and they make this note for the TL2X-SAP : The field number for these objectives represents performance over the full operating wavelength range with no vignetting over the entire field of view.

So that is optimistic the field will okay out father than 22mm.

I'm glad to see someone else taking a risk with their money to try something new! =D>

After trying the Nikon Plan APO 2x/0.1 and having coverage problems I am staying away from 2x objectives. The Nikon was rated for a 26 OFN. #-o

If that Thorlabs 2x was the 10X Super Apochromatic (0.5 NA) instead I would have went for it. :-k


Best,

Robert

Scarodactyl
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Re: Thorlabs super apochromat 2x

Post by Scarodactyl »

I figure the market for them outside of photomacro is strong enough that it's not too great a risk. And if it's great I can sell off my mitutoyo 2x and/or Optem 2.5x (much as the latter would pain me). Given how the SAP objectives are a weird mishmash in every other spec I figure odds are good they don't have a consistent field number either.
Ha yeah, that 10x super apo is one of those holy grails. Doubt I'll ever get a chance to try one.

RobertOToole
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Re: Thorlabs super apochromat 2x

Post by RobertOToole »

Scarodactyl wrote:
Thu Jun 23, 2022 5:00 pm
I figure the market for them outside of photomacro is strong enough that it's not too great a risk. And if it's great I can sell off my mitutoyo 2x and/or Optem 2.5x (much as the latter would pain me). Given how the SAP objectives are a weird mishmash in every other spec I figure odds are good they don't have a consistent field number either.
Ha yeah, that 10x super apo is one of those holy grails. Doubt I'll ever get a chance to try one.
When the 10X Super APO first came out I called them and try to get them to send me a loner, they dont do loaners. #-o

I'm sure they do for big customers but not to some random person.

Thorlabs did say they have a 30 day money back guarantee though so you can send it back without any re-stock fee.

Best,

Robert

Scarodactyl
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Re: Thorlabs super apochromat 2x

Post by Scarodactyl »

Summary: It's good!
Before we get going let's contextualize this objective. 2x is a difficult magnification range for objectives since you need to fit a 100mm effective FL into a 95mm, 60mm or even 45mm space depending on your system.
The familiar option is the Mitutoyo 2x (widely available, not super expensive, not very good) and its various clones (never seen anyone post test results but no doubt they are similar)--these have the same form factor and 34mm working distance as a 5x m plan apo.
There's the Optem 2.5x which is vanishingly rare but improves on the mitutoyo's resolution and color correction, though with weak corners and no planarity--it also has a very short body and long working distance. It's pretty much a single doublet as far as I can tell (??) which seems like a miracle.
Olympus offers a 2.5x/0.08 Mplanapo with a 10.7mm working distance and a 2x/0.08 planapo with 6.2mm working distance--I have actually owned both but the systems they were on sold quickly and I didn't get a good test with direct projection since I was between photo rigs at the time. As I recall both looked fine through the eyepieces.
Nikon also offers a 2x/0.10 apo which Robert has reported has terrible coverage (see posts above).
Then there are the hypothetical options: The Navitar 2x/0.08 HR apo with 39mm working distance, the Mitutoyo QV HR 1x/0.084, or the Seiwa 2.5x/0.08 HR, objectives which just haven't fallen into the hands of photomacrographers. The Thorlabs 2x/0.10 super apo with its imoressive 56mm wd was in that latter category until this week when a couple hit the market at 450usd, expensive but not as bad as e.g. the Mitutoyo QV 1x HR on eBay for $5999.

So to test this I ran it head to head to head against the Mitutoyo 2x and (where possible) with my Optem 2.5x objective, on aps-c with my Canon Rebel T7.
Image
First impressions: Planarity of the superapo isn't quite perfect in extreme corners, though it's a lot better than the optem. No visual degradation in corner quality with superwide eyepieces. The optem actually looks brighter, and I suspect they might have lied on its specs and the Optem's NA is larger than 0.09. The thorlabs shares the optem's short length and very long working distance.

Wafer shots!
Center 100% crops:

Mitutoyo 2x:
Image

Optem 2.5x resized to match:
Image

Thorlabs 2x:
Image

The mitutoyo is here to show a typical 2x underperformer. It's OK in some contexts but doesn't resolve well. In contrast the Optem 2.5x has excellent resolution in the center and appears to edge out the thorlabs super apo (another reason to suspect the Optem is higher NA than marked).

Two sets of corners:
Mitutoyo 2x:
Image
Image
Thorlabs 2x:
Image
Image

This is the shot we all wanted to see. The mitutoyo does poorly as we knew it would and the Thorlabs objective passes with flying colors IMO. There may be a hint of distortion (or maybe the Mitutoyo 2x has some distortion, they don't match anyway), but CA in the corner is minimal and resolution is very nice with the Thorlabs.

So we could get the Optem in the mix I also looked at an Optem corner crop vs a not-quite-corner-crop on the mitutoyo and thorlabs. I should have moved the subject to get the same corner region with the Optem but I didn't. This makes it technically unfavorable to the Optem but it's generally accurate. The optem's corners have distortion but beat the mitutoyo on CA.
Mitutoyo:
Image
Optem:
Image
Thorlabs:
Image

I took some 'pudding' shots on a sunstone with coaxial illumination but they're harder to compare because the three objectives give pretty different results when used this way. The thorlabs has poor illumination coverage unless I completely remove the aperture stop. Here are thumbnails to illustrate that:
Mitutoyo:
Image
Optem:
Image
Thorlabs:
Image
Center followed by corner, mitutoyo has been brightened in the corner.
Mitutoyo:
Image
Image
Optem:
Image
Image
Thorlabs:
Image
Image
At the center the optem has a slight edge, in the corner the optem's smeariness does affect resolution. The thorlabs' slight red glow appears to be from a mistake in stacking, not a problem with the objective.

Overall I think it's fair to say the Thorlabs' 22mm fn is pessimistic. It doesn't work with my DIC and coaxial illumination is a little annoying but boy does it perform. I am sure there are non-objective solutions much better and cheaper but this is probably the first properly good 2x objective I know of.
Last edited by Scarodactyl on Sun Nov 13, 2022 10:50 pm, edited 3 times in total.

Lou Jost
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Re: Thorlabs super apochromat 2x

Post by Lou Jost »

Thanks very much for the very informative test! I hope they appear more often on the used market.

rjlittlefield
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Re: Thorlabs super apochromat 2x

Post by rjlittlefield »

Scarodactyl wrote:
Mon Jun 27, 2022 4:22 pm
Summary: It's good!
Indeed. And that all looks like good testing too. Nicely done!
I am sure there are non-objective solutions much better and cheaper.
Noting that NA 0.10 is equivalent to effective f/5.0 on the subject side, I'm thinking that a lot of stacked lens combos would work fine.

--Rik

PeteM
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Re: Thorlabs super apochromat 2x

Post by PeteM »

Thanks for that test, Stephen.

Congratulations, too, on buying a fairly pricey lottery ticket and having virtue rewarded :-).

Scarodactyl
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Re: Thorlabs super apochromat 2x

Post by Scarodactyl »

Thanks! It did go better than I'd feared, though unlike lottery tickets this lens would have resale value even if it only covered 22mm. People buy Mitutoyo 2xes after all.
Incidentally I figured out why it and my optem don't work with my DIC system. Their back focal plane (? wherever the prism needs to go) is a ways behind the lens.
Image
Held here I get nice even DIC with the Optem.

PeteM
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Re: Thorlabs super apochromat 2x

Post by PeteM »

Scarodactyl wrote:
Tue Jun 28, 2022 1:23 pm
. . . Incidentally I figured out why it and my optem don't work with my DIC system. Their back focal plane (? wherever the prism needs to go) is a ways behind the lens.
Image
Held here I get nice even DIC with the Optem.
Found that by sheer luck?

In any case, good to know. I'll likely try putting low power infinity objectives on extensions, maybe a helicoid.

Scarodactyl
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Re: Thorlabs super apochromat 2x

Post by Scarodactyl »

I just had a hunch. The mitutoyo 2x does work with DIC which is probably a design requirement that constrained others.

PeteM
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Re: Thorlabs super apochromat 2x

Post by PeteM »

Sheer luck? Shear luck! It's excellent that you'll be able to have DIC with this objective, even if on a long extension.

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