Bigbeartom44

I read many reviews of lenses and they always break the quality down by Center, mid section, and Edge. When does the Edge start? Is it 5%, 10% or 20% or something else. I can live with 5% or a little more but not 20%.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Edge is usually left and right edges, and then there are corners which are often rated as well. The top and bottom edge are closer to the center, so they are not generally considered when describing edge performance.

Leitz Loc: Solms

RWR Loc: La Mesa, CA

My Rolleiflex negatives must be an anomaly!

Charles 46277 Loc: Fulton County, KY

I always assumed the terms divided the image in thirds. The significance depends on the use of the lens as well as the stats. For traditional portrait work, the edges don't matter, and on view cameras, lenses were often wide open for portraits, even though they were not at all sharp at the edges that way. Today, the traditional portrait look has to be achieved by other means (very large apertures, or greater distances for the backgrounds, etc.)

I sometimes use a digital attached to the back of a view camera. The image is so large and the sensor so small, that the center of the image is all that could ever be used. The same applies for macro work if a bellows or extension rings are used--only the center of the image is used.

Of course, there are times when we want corner to corner sharpness to a high standard. Lenses may need some testing for that. In most cases, I think, The sharpness in different parts of the image will shift with aperture changes, so if you improve the corners, you lose some of the center. View camera lenses have published test results on this, but I have not seen published lists for today's digital lenses.

The chart below tested many familiar view camera lenses for resolution in center, middle, and edge--at f11, f16, and f22. They never tested any of them wide open or stopped down all the way, but you can get an idea from the three f-stops shown how the variation would go. You can also see that even the most expensive lenses varied greatly by f-stop. When lenses were used at large apertures, they were either for portraits or sports action, where the subject is almost almost always in the center (and the rest is unimportant). A product photo or architectural views would always be shot at optimal apertures (same with macro and landscapes). I have not found (in casual use) any of my Canon digital lenses to be sharper than the prime Schneider view camera lenses when both are used on the Canon digital sensor--but of course the sensor only sees the center of the view camera lens image, even with movements.

Note that the 135mm Nikon W at f-11 resolved 15 lines per mm at the edge, while the Fuji resolved 60 lines. But other f-stops show other results.

http://www.hevanet.com/cperez/testing.html

jerryc41 Loc: Catskill Mts of NY

Not when you use it to shoot in portrait mode.

RWR Loc: La Mesa, CA

Aha!!

speters Loc: Grangeville/Idaho

There are tests just like these for about all of todays modern, "digital" lenses!

bull drink water Loc: pontiac mi.

large and medium format cameras had no real problem with the issue. a few camera had curved film planes. if became a real issue with the 35mm cameras. in digital it's not too much of a problem with aps-c or smaller sensors. with full frame cameras it's an issue. a few years ago I advocated curved sensors, this last year I've read that a few manufacturers working on the idea.