View Full Version : Image Circle Sharpness?

Gary Albertson
17-Jan-2001, 18:35
Gentlemen, I have another rather naive question. Can I assume that the smaller the image ci rcle for any particular lens results in finer, sharper details? I have a tendency of not using much movements, so ima ge circle is only somewhat importlant, but if the lense does have a much larger image circle than I ever wi ll need, am I sacrificing sharpness and detail? Might I be better off with lenses like the 200M Nikkor, unless the o ptics/glass are not comparable to perhaps the 210 Nikkor or others with larger IC. Sure, the weight and filter siz e are also important, amongst other considerations, but how about just sharpness and deta

Doug Paramore
17-Jan-2001, 21:09
Gary: You are probably right that the image sharpness drops off a little as you near the edge of the image circle, but that is not much of a consideration with LF photography. The modern lenses are usuable with considerable movements. I don't make any prints larger than 16x20, and sharpness or lack of it is not a problem with that size print if movements are used in the camera. If you are shooting LF, the day will come when you will need full movements. I much prefer to have the larger image circle and not use it than need them and not have it. I shoot primarily scenics, and even with the scenics I find I use lens rise and tilt a great deal. I could live without a lot of movements with scenics, but some scenes will not look like I want them to look.

Glenn Kroeger
18-Jan-2001, 02:11

If I read your question correctly, what you seem to be wondering is if a larger image circle is a trade-off for better performance in the center of the field. The answer is no, not in any systematic way. It depends entirely on the design of a particular lens.

In general, lens designers don't allow a lens to be worse in the center to get better edge performance. In fact, generally the better the lens is in the center of the field, the better it will be any distance out from the center.

A counter example is when comparing lenses of radically different optical design. Some wide angle designs aren't as absolutely sharp as narrower angle designs. For example, a 90mm plasmat with a small image circle designed for digital work can be sharper than a 90mm wide angle designed for 4x5.

On the other hand, the 110XL Schneider has a very large image circle but in the center of the field, it is as good or better than any other lenses in that general range of focal lengths.

So you can't assume for example, that the 200 M Nikkor is going to be sharper than a 210 W Nikkor, or 210 Apo-Sironar-S just because it has a smaller image circle. In fact, all three of these are probably about equal in the image center, perhaps with a slight edge to the Apo-Sironar-S as it is the latest of these 3 designs and uses somewhat more exotic glass to achieve its wider image circle.

Erik Ryberg
18-Jan-2001, 02:34
Lenses with larger image circles will be throwing more light in your camera. So theoretically there will be a little more flare from the light bouncing around off your bellows. But practically I don't think it would make any difference, unless your bellows are made of reflective material, which would be, um, unusual.

Pete Andrews
18-Jan-2001, 06:55
I think camera flare affects image quality a lot more than most people realise. I've seen a lot of debate over which lens has the 'best' MTF curves in this forum, but the fact that the camera body can degrade the contrast of any lens seems to have been shrugged off as unimportant.BTW Gary, I have to take issue with you addressing us all as 'gentlemen'. I'm sure a lot of female readers have been quite insulted by the implication that they are incapable of answering your questions.

Glenn Kroeger
18-Jan-2001, 09:33
No question that Eric and Pete are correct (Pete being Politcally Correct as well) that flare is an issue. Use of a compendium lens shade can visually improve image contrast and should be used whenever possible. Just because Ansel only used his hat doesn't mean that you cannot do better with proper lens shading.

Sean Billy Bob Boy yates
18-Jan-2001, 12:49
- "BTW Gary, I have to take issue with you addressing us all as 'gentlemen'. I'm sure a lot of female readers have been quite insulted by the implication that they are incapable of answering your questions."

Not to mention those of us human males who could never be described as gentlemen!