Willfull misuse of some finite objectives

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JKT
Posts: 203
Joined: Fri Oct 28, 2011 9:29 am
Location: Finland
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Willfull misuse of some finite objectives

Post by JKT »

I had some spare time, so I did some testing. Namely I tested four finite objectives with infinite setup with four different tube lenses.

The used tube lenses were all Schneider-Kreuznachs: Componon-S 135/5.6, Componon 150/5.6, Componon 180/5.6 and Componon 210/5.6. The first was metal construction with star-shaped iris and the others black metal with chrome filter ring. In all cases the objective was as close to tube lenses as possible with basic parts (## to T2 StepDown & T2 to RMS flat adapter).

The camera used was Canon EOS RP (FF, 26MP) and all images were stacked. The results are shown in matrix form, where rows represent tube lenses (in previous order) and rows are crops at different locations; center, long edge, near short edge and extreme corner. The center of crops is located at r= 0mm, 11.3mm, 16.0mm and 20.6mm. Raw images were stacked in Helicon and the result saved as DNG. This was then processed with PhotoShop without any sharpening and identical settings (except exposure) in all images. The crops are 1:1.

First tested objective is LOMO Apo 10x/0.30. As expected, this is completely unusable. It requires corrective eyepiece as finite and using it as infinite sure won't help.
LOMO 10x.jpg

The second objective is Nikon 10x/0.25 achromatic finite conjugate. The center is decent and contrasty, but the sharp image circle is not very good. With the first tube, the corners are pretty much black.
Nikon 10x Finite Conjugate.jpg

The third objective is LOMO 8x/0.20. It has low contrast, but sharpness in center seems decent and the good image circle would be acceptable on crop sensor. Even on full frame the corner behaviour is much better than with the previous two. As infinite on 200mm tube this would be 11.1x/0.22, which is on the low side.
LOMO 8.0x.jpg

The last finite is naturally LOMO 3.7x/0.11, which becomes 6.1x/0.14 on 200 mm tube. Previous reports of nice behavior as infinite are confirmed here as well. Contrast is not that good, but the sharpness is there. The extreme corners are suffering especially on the first tube, but visibly on the next two as well, but the r=16 image is only suffering on the 135 mm tube.
LOMO 3.7x.jpg

The last set is comparison to genuine infine - Mitutoyo MPlan Apo 10x/0.28. The center is sharp and has more contrast compared to LOMO 3.7x, but the extreme corners are clearly worse. Interestingly, it seems that for some reason Mitutoyo doesn't like the 210mm tube lens. This doesn't seem to happen with LOMO.
Mitutoyo MPlan APO 10x.jpg
Comments?

Macro_Cosmos
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Location: Sydney

Re: Willfull misuse of some finite objectives

Post by Macro_Cosmos »

I can comment on the Mit 10x and tell you that the corners do not resemble both copies I used to own. Both were the newer "-3" version, also purchased new.
While the corners aren't great, they are decent and, it's not the sharpest but it's robust -- meaning I don't see the kind of aberrations resembling camera shake (spherical aberration?) You're using it on a 210mm TL, technically the corners should be a tad better?

JKT
Posts: 203
Joined: Fri Oct 28, 2011 9:29 am
Location: Finland
Contact:

Re: Willfull misuse of some finite objectives

Post by JKT »

I am not too happy about the corners either. It is hard to say whether that is due to the Mitutoyo or the tube lenses. After all, the long ones are almost 60 years old and I have only those and the two Raynoxes. Canon 250D doesn't really count.

Camera shake shouldn't be an issue with flash.

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