Image Circle

[A. Mouton]

The image circle of a lens is usualy given at f:22. Does somebody know how the i mage circle change as a function of the f stop? Andre ( from France).

[neil poulsen]

All that I've seen published is giving the image circle for two different f-stops. It depends on the lens formula. You can always do some tests on your view camera to determine the difference. I offset my 4x5 back by a known amount, and then I apply a small tape "arrow" to the back. I set the f-stop and then move the arrow down on the ground glass until, looking through the front of the lens, the rim(s) of the lens begin to obstruct the view. Then repeat for the next f-stop. It helps to place a lamp behind the ground glass so that you can see the "arrow's" shawdow.

[giancatarina]

i agree with that: All that I've seen published is giving the image circle for two different f-stops. It depends on the lens formula. but not with the test, because this will give you the larger image circle available, but with some lens, the quality decrease badly far from center. with the digital serie, Schneider are very conservative, because digital sensors require more detail, if you use today film, the image circle is larger that they say http://hv.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id= 005br8

[Mike Mahoney]

Andre, a short time ago there was a thread dealing with this very question, and quite a number of posters weighed in. I don't remember the name of the thread, but you may want to check the archives under lenses.

[giancatarina]

http://hv.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=004R5q