non digital lenses on a digital back anyone

[adrian tyler]

there seems to be a lot of people out there who use older lenses with different characteristics. i have a two questinons nagging me for a while now:

has anyone experimented with older lenses on digital capture backs? do they retain their characteristics on the smaller sensors?

is there a significant difference between modern "non-digital" lenses and "digital" lenses?

thanks

adrian
http://www.adriantyler.net/

[Gene McCluney]

I have a Betterlight scanning back for 4x5. I don't have any "digital" lenses. Most of the lenses I use are Commercial Ektars which could be as much as 50 years old. I get excellent results using any lens. In my opinion "Digital" lenses are generally wider focal lengths with smaller coverage circles, and other than that are no different, when it comes to lenses for 4x5 format cameras.

On my digital SLR (full frame 35mm format) I use whatever lens I want. In consumer DSLR lenses, the "digital" label usually means a smaller image circle because the majority of imagers for 35mm format DSLR's are APS size, not full-frame. There is no disadvantage to using regular lenses with an APS size imager.

[Jack Flesher]

Like Gene, I used my "regular" LF lenses when I had my Betterlight. I however did buy some older specalty glass to get "the look" -- and yes, those lenses imparted their look to the digital file.

[Ken Lee]

What is the look ?

[Jack Flesher]

Soft-focus lenses are probably the easiest example and those results have been shown over the web. However when comparing the look from "normal" lenses, the differences are more subtle and thus tougher to explain with words or show on the web, and you usually need to be viewing a print to see it -- and even then it is different for different lens designs...

I believe the differences are due to a combination of factors; lens design, coatings and manufacturing methods available at the time the lens was built. Dagors are probably a good example: If you compare a Dagor shot with one from an equivalent length plasmat, you will see a kind of buttery smoothness in the tonality that isn't in the plasmat shot. Compare a coated tessar with a comparable plasmat and you will probably see a sharper, higher contrast central area that tapers to smoother, less sharp image at the outer edges.

Cheers,

[Oren Grad]

There is no disadvantage to using regular lenses with an APS size imager.

http://theonlinephotographer.blogspo...great-for.html

Re the 36x48 sensors that are found in high-end backs, Rodenstock claims that design of their "digital" lenses is optimized to address several issues:

(1) reducing chromatic aberration to less than the pixel dimension
(2) enhacing performance at wider stops (f/8 or f/11) to minimize diffraction losses with the shorter focal lengths needed for small sensor formats
(3) minimizing curvature of field for these rigidly planar sensors

Also, with the HR series in particular, the design is supposed to take into account the properties of the CCD cover glass.

The Rodenstock literature happened to be handy, but I'm sure Schneider addresses the same issues with its Digitars.

These are the theoretical arguments. I don't know of any test report that has compared non-digital and digital lenses in the same focal lengths to determine how much of an advantage you really gain.

[Ken Lee]

Dagors are probably a good example: If you compare a Dagor shot with one from an equivalent length plasmat, you will see a kind of buttery smoothness in the tonality that isn't in the plasmat shot. Compare a coated tessar with a comparable plasmat and you will probably see a sharper, higher contrast central area that tapers to smoother, less sharp image at the outer edges.

I'm familiar with the Tessar, since my medium format 1950's folding cameras have lenses of that design - but are there any examples on the web which nicely demonstrate the qualities of Dagor lenses ?

[Bruce Watson]

Is there a significant difference between modern "non-digital" lenses and "digital" lenses?

I don't know how significant it is, but one theory is that when designing lenses for digital sensors one has to take into account the nature of the sensor itself. Mostly that means that digital sensors have some 3D aspects where film is more planar. This is particularly evident in wide angle lenses.

Apparently with conventional (film) wide angles, the incidence angle at the edges of the sensor can be large enough that capture efficiency is effected. That is, (some) light doesn't make it down the sensor wells. At least some digital lenses are designed to correct this somewhat pulling the incidence angle up closer to 90 degrees.

The other thing is that the location of sensors in the arrays is deterministic, whereas the light receptors of silver halide films are arranged stochastically. What this means to lens design is that some aberrations might become more visible and others less so when using digital sensors.

To answer your question directly, the reason to use digital lenses with digital sensors is that one gets the best performance from a system by designing the component parts to be part of that system. Whether or not one needs and/or wants the best performance (or defines performance in other ways, like an "old look") is a question best left to each individual photographer.

[Jack Flesher]

FWIW, I tested a few Rodenstock and Schneider digital-specific lenses with my Betterlight. The Betterlight is not the best test-bed for these as the maximum resolution of the back is about 60 LPmm, but in all cases these digital-specific lenses resolved to the maximum of the sensor inside the stated IC.

However, many of my "normal" modern lenses also resolved to that 60LP limit -- as did my "older" Gold-Dot Dagors. Even an old convertable Linhof branded 150 Symmar made it, but only at f11. CA varied, but for the most part was not an issue with any of the APO plasmats, though did show up in varying degrees with the older designs.

Cheers,

[Jack Flesher]

are there any examples on the web which nicely demonstrate the qualities of Dagor lenses ?

None that I know of. I tried to post one once by showing a 100% crop, but it really didn't show very well online. Best thing to do short of trying one yourself is to ask others who have used them for their feedback and draw your own conclusions from that --