also bear in mind that the edge crop is on an 810 film, anything smaller one will be using far less of the image circle.Originally Posted by Mike1234
also bear in mind that the edge crop is on an 810 film, anything smaller one will be using far less of the image circle.
Wait a tick... you're saying these lense cover 8x10 or you're just cropping to the outermost areas on which an image is recorded?
No, non of these lenses cover the entire 8x10 frame. I started with a single spot on the SA and found the area on the other two since they other two have larger IC.
Here they are in alphabetical order;
The lower resolution of SA 90/8 in the corners in my original post, I bet, was due to its strong field curvature, as I've seen in many pics taken with that lens. My experience with SA90/8 is that some items (usually grass/leaves on the ground) which are much closer than where the perfectly flat focus panel should be, often ended up being much sharper than the infinity on the corners, even though the lens was in fact focused to infinity. Nikkor-SW 90/8, in contrast, has a much flatter image field, and therefore is less prone to the curvature problem.
In my pics, both lense were focused at infinity, and the car and tree leaves on the bottom left and right corners were fairly far from the camera, as I was taking pics from a highrise building. Therefore, the resolution on these objects (the car and tree leaves) would be seriously affected if a lens had strong field curvature, which was indeed the case for SA 90/8.
In your example, however, the leaves on the ground were very close to your camera. as a result, the resolution was much less prone to the field curvature of SA 90/8 - in fact SA 90/8 might even gained an advantage compared to the Nikkor in your case due to its field curvature.
Taking all these together, I'm not surprised to see roughly the same performance from SA and Nikkor in your test...
I'm late to the party on this thread (by over two years!) and found it while searching for info on diffraction limits of my Schneider SA f8. I haven't had the chance to print or scan any of the images I've taken with mine yet, but have been wondering if I've been using it at optimum aperture. I pretty much only shoot at f22 out of habit but have read several posts that say f16 is far sharper at the plane of focus if fine detail in that area is critical. Would this be true?
It could very well be true. Try it and see.
Yet another example of the amateurish attempts to decide sharpness of a lens, nothing more than that.
Wooden field cameras of this kind don't have the rigidity necessary to perform sharpness tests. To take a lens with its lens board out the front standard and to put there a new lens is enough to change slightly either the standard tilt or the focus. Let alone the fact that the two lenses don't have the same FFL and if you need to refocus there it is - you introduce another source of imprecision again. Not to speak either about another film holder being put on the camera, a different film bulge in it etc. etc.
Just try to take 2 pictures with the same lens (taken and put back on the front standard, refocused) and see for yourself if they are the same...
Even better - make a double exposure on one film in this way and see for yourself if the sharpness didn't change.
The OP's lens test is technically worthless.
Were you expecting otherwise from an internet forum?
Social Engineer
Not really, just to make the point...
GPS, I think your not perfectly on the mark. With a well maintained camera, on a still day, with a decent ground glass, and careful focus, the OP's test has some validity.
Now unit variation may have an impact on the test, but the effort was not entirely wasted.
Sure you can use an optical bench, but that not very real world either. The benefit of the Nikon 90 (to me) is the larger image circle and that its a bit sharper in the outer parimeter.
Hell theres lots of variables, film holder for example...
But I and other have bought lenses based upon a impromptu test shot.
Yes, I've owned both.
bob
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