Digital vs normal lenses

[Neal Shields]

Schneider says that their Digitar lenses provide superior resolutation that digi tal backs need. Superior to what? I have looked on their web site and compaired their 90mm Digitar lens to their 90mm Super Angulon. One is measured at 4.5 an d the other 5.6. I split my screen so that I could look at the charts side by s ide, and I really can't see the Digitar advantage. I am not however an expert o n optics. Some other web sites that I have looked at make it sound like if I don 't run right out and buy digitally optomized lenses, I might as well shoot with broken pop bottle bottoms. I would be very interested in what you guys think.

Neal

[Glenn Kroeger]

Neal:

From what I have gathered corresponding with Schneider and Rodenstock reps is that the real advantage of these digital lenses is slightly better performance at higher spatial frequencies (40-60 lp/mm) at larger apertures (f/8-f/11), in exchange for smaller image circles. So at f/22, they're all diffraction limited, but for shooting at f/8, the digital lenses will deliver slightly better performance. Whether this is observable on roll film is a subject of controversy... some say yes, others say probably not, since film flatness and other variables will likely be greater than the performance difference.

[pat krentz]

I have a friend who has a Hassy with the 150mm lens and I have a Kowa with the 150mm lens, we photographed the same subject with the same film and printed our negs on the same enlarger with the same lens and there was no visible difference, forget the advertizing, check the prints. Pat

[Robert A. Zeichner]

Neal, I'm curious....what camera/back are you intending to use these lenses with?

[Neal Shields]

No, I am not in the market for a new lens. It is not a new lens that my photography needs, it is a new photographer. I have even taken a plastic lens out of a cheep Polaroid, mounted it to my Linhof, and shot with that. Even then, my photography doesn?t seem to suffer. So I expect it will be a while before I grow out of my Angulons etc.

However, while waiting for some talent to miraculously appear, I occupy myself trying to understand the craft side of the equation.

Everything I have read about ?digital? lenses says that they are better for both digital and film. Comparing the graphs on Schnider?s web site, (which I thought I was beginning to understand), the data doesn?t seem to support this.

The only thing that I can see that could improve a lens for digital would be moving the nodal points as in a reverse telephoto in order to change the angle of the light ray hitting the pixel, however, I would expect that to result in a disadvantage for use in film photography.

[Bob Salomon]

"Everything I have read about ?digital? lenses says that they are better for both digital and film. Comparing the graphs on Schnider?s web site, (which I thought I was beginning to understand), the data doesn?t seem to support this. "

Then you may find that Rodestock's detailed brochure with illustrations of the differences will make it clear for you.

But it will have to be mailed.

It was written and illustrated by Dr. Walter Schoen

[Thilo Schmid]

Neal,

image circle size and resolution are two contradictory goals in lens design. The past development (and market need) of large format lenses has mainly lead to larger image circles and less increase of resolution. The smaller digital sensors will not need large image circles any more. Large Format is currently downsized to a sole "View Camera" with a stress on DOF and perspective control - don't even considdering a Ground Glass.

Since the pixels on these modern digital sensors are more tightly packed than most film grain, they require higher lens resolution. Due to the Sampling Theorem, the regular arrangement of these pixels do require even more lens resolution compared to the random spread film grain.

So these "Digital Lenses" simply have other design goals. If you are shooting Roll Film than you might be happy with digital lenses, too. If you prefer Sheet Film, forget about them.

Regards,

[Glenn Kroeger]

Neal:

I am curious what graphs you are comparing, since most "normal" view camera data sheets don't give information for spatial frequencies higher than 20 lp/mm. It is the 40-60 lp/mm range that "digital" lenses are designed to optimize.

Glenn

[Neal Shields]

http://www.schneideroptics.com/photography/large_format_lenses/super- angulon/56_90/mtf2.html

http://www.schneideroptics.com/photography/digital_photography/90/page 5.php

I am compairing the MTF graphs on these two pages. From looking at them, even adjusting for the one stop difference it would seem that the Angulon is better? I have always read that MTF was a better measure of resolution than LPM because one required a subjective judgement by the viewer and the other could be done objectively.

Sinse they are both Schneider measurements, one would assume that there are no other measurement variables that would give one an advantage over the other.

Neal

[Thilo Schmid]

Neal,

as Glenn pointed out, you have to look at the right curves. In The MTF-Graph of the Super-Angulon, the line belonging to 20lp/mm is the lowest and in the Digitar it is the top most line. The Super-Angulon Chart do not show lines for 40 lp/mm and 60 lp/mm. And if you compare the two lines for 20 lp/mm you can easily see that the Digitar has better resolution, especially when looking at dotted line of the tangential frequencies.

Regards,