Interesting article on Luminous Landscape about scanning digital imaging. What design parameters of Schneider's Digital LF lenses makes them better for this purpose?
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Interesting article on Luminous Landscape about scanning digital imaging. What design parameters of Schneider's Digital LF lenses makes them better for this purpose?
they're designed for a lower angle of coverage than large format optics, since the only need to cover the smaller digital sensors. this allows them to be much better corrected than large format lenses. they are especially well corrected for lateral chromatic aberration, since this can cause dramatic problems under some circumstances with digital capture (like a whole row of pixels containing nothing but red fringe).
If you look very carefully at the mtf graphs on Schneider's sites you will see that the graphs are in % of image height. At first glance the lenses look like some kind of major optical breakthrough when compaired to regular LF lenses. However, if you then look at size of the image circles you see that the "digital" lenses are basically medium format lenses in large format mounts.
The logic goes that you want an image equally sharp accross the photograph so it is a waste to make the center of a large format lens as sharp as possiable if the edges would be notically worse so they make compromises with center sharpness to balance the edges.
Even so when you adjust the graphs from % of image height to actual image height the "digital" lenses are not that much better than the center of a good 4x5 lens.
They just can read the Bino speach better:++0000+000+0++0+++00+
Just joking!
"Even so when you adjust the graphs from % of image height to actual image height the "digital" lenses are not that much better than the center of a good 4x5 lens."
actually, they're way better. take another look at the frequencies that are being graphed.
paul is write.... the digitar lenses started a new trend in MTF... instead of 5 10 20 lp/mm, normal for most LF lenses, Digitar MTF's have been pushed to 20, 40, 60 lp/mm..... and yet the Graphs almost idential, so its about triple the performance, so, I would consider it an optical breakthrough.
the guys i talked to at schneider don't go as far as calling it an optical breakthrough (i love the german engineers ... there's no b.s. with them). they seem to consider it a refinement that gets the most performance possible out of a specialized design. the performance of these lenses is closer to the performance of the best 35mm lenses, and they're able to do it because the angle of coverage is closer to that of 35mm lenses.
they showed me some amazing examples of photos taken with a new prototype digital lens that could resolve over 200 lp/mm at +50%mtf. the catch was, the angle of coverage was only enough cover the fingernail on your little finger. it was designed for some specialized kind of camera that has a tiny, high-density sensor.
for wider coverage lenses, designed for large format, they're already giving us the best lenses they know how to make (at prices we're willing to pay, anyhow).
Paul, the secret does seem to lie in the image circle....the bigger the image circle, the more the resolution is spread apart. Of course, at times this can be advantgeous, but now that digital sensors have such high pixel density, they have far exceeded what film can resolve, which enables the use of shorter fl's lenses for the same composure and final print resolution. This is a huge benefit the field has not seen in quite some time..... Digitar lenses will further this exploitation of much smaller camera systems with equal or better image quality then larger systems.