8x10 Lenses Most Used, Most Desired

[Dan Fromm]

Neil, if there are standards for measuring coverage they're not in the common language. When posters here talk about circle covered some mean circle illuminated, whatever that means, others mean circle with adequate image quality at the edges, whatever that means. Both concepts have room for ambiguity.

In addition, what sellers mean by "covers" isn't always what users mean. The clearest case is that of a person who posted here and sold on eBay as landarc. landard sold 180/6.8 Dagors on eBay with the claim that they covered 8x10, started a long and hilarious discussion here with a complaint that his 180/6.8 Dagor didn't cover 8x10.

At one time I thought that a lens maker would apply the same coverage standard to all of its lenses. I can't prove it. For example, Rodenstock seems to have used an MTF-based standard to estimate coverage. Coverage stops where the MTF at some resolution or other is low, whatever that means. Then I looked in some Rodenstock brochures. The Apo-Ronar brochure shows, for example, MTFs that are high and don't decline much across the field for, e.g., 1000/16 and 1200/16 Apo-Ronar CLs, MTFs that drop nearly to zero at the edge for, e.g., 480/9 and 600/9 Apo-Ronar CLs. The 75/4 Apo-Rodagon-D's MTF curves are very high and very flat across the field; I've had one, b'lieve that a field stop limited coverage, i.e., IIRC the lens put no image outside of the circle R'stock claimed it covered.

There's a semi-standard about what constitutes sharpness in the final print. ~ 8 lp/mm at reasonable, whatever that means, contrast. Assuming a perfect enlarging lens, and how much the negative is going to be enlarged its easy to calculate what this means for resolution in the negative.

ULF is often contact printed, but not always. For example, Clyde Butcher prints enormous from 11x14. I've been to his Big Cypress shop, noticed that the subjects in his prints' corners have little detail. That's one way to finesse a lens' lack of coverage (in the sharpness at the edges of the circle sense). People who post images here to show their lenses huge coverage often do the same.

Sharpness is considerably overrated. It can be quantified, so is easy to pay attention to. Some of my most effective prints are soft all over. Strong image can beat fuzz. Sometimes.

[Greg]

This is what interests me. I've asked in the past, and it appears to me that claims of huge image circles for these lenses, for the Computar f9's, Kowa Graphics, etc., are for contact prints. But, I wonder how some of these claims would fair if an 8x10 image were enlarged?

Of course, making claims only for contact 8x10 prints is certainly legitimate, given their acceptable viewing size and their prominence. But I suspect most mfg image circle claims take into account some degree of enlargement. (Not sure what? Is there a standard?)

For me am more and more making Digital Negatives for printing on Printing Platinum/Palladium. I have been making the Digital negatives based on Dan Burkholder's The New inkjet Negative Companion including a step tablet to the side of the image. This allows me to crop and enlarge the initial image. For me I base my criteria of judging my negatives for sharpness with the assumption that I will be able to reproduce the image by 200%. This is one reason I do not judge the performance of my lenses by making contact prints. After some practical tests, I know how much sharpness the negatives must have to be possibly "enlarged" by 200%. Most measurements for coverage listed by manufacturers is for f/22. My maximum enlargement of 200% allows me to stop down to f/64 with my lenses of 180mm and longer and this gives me greater coverage measurements.

Recently did a lot of research for a second time on Computer f/9s, Kowa Graphics, etc. and decided not to go in that direction. Seems like there were several undocumented changes in the generations of these lenses, plus they seem to command rather high prices now. Only had a chance to try one of these optics long time ago, and my particular sample did not cover 11x14 even though I know of others using the "same" lens on 11x14 and experienced full coverage.

Really great source of info is in "The use of Historic Lenses in Contemporary Photography" by Paul Lipscomb.

Would also love to know the answer to your question: "Is there a standard?" So far it's alluded me....

[Luis-F-S]

Sharpness is considerably overrated. It can be quantified, so is easy to pay attention to. Some of my most effective prints are soft all over.

+1!!! The less experience, the sharper they want the lens they buy to be! L

[Greg]

Agree with Dan Fromm's longish very well done post. I once worked with a photographer (also a RIT graduate like I), who used to test his aerial lenses by shooting USAF lens test charts from 12 feet away, but then went to actually used his equipment shooting from planes.

"The human eye generally is considered to have a resolution of 10 to 14 lines/mm at a viewing distance of 10 in." Page 117 from Stroebel's VIEW CAMERA TECHNIQUE

[neil poulsen]

I think my comments are more muse than pointed discussion. Summarizing, I generally feel comfortable with mfg specs, which I think must assume some degree of enlargement. With some notable exceptions (e.g. G-Claron?), they seem to work in practice.