View Full Version : Circle of confusion

Terry Lorch
11-Jan-1998, 21:30
I want to know the circle of confusion for 2 lenses:

Speed Graphic 4x5 Graflex Optar 203mm f/7.5 Speed Graphic 4x4 Graflex Optar 135mm f/4.5

These would allow me to calculate hyperfocal and depth of field charts.

Any help would be appreciated.

Terry Lorch Terr725@aol.com

Rob "John Henry" Rothman
12-Jan-1998, 10:42
The circle of confusion is not a property of the lens itself. Rather, it is a m easure of how critical you, the photographer, want to be. Hyperfocal distance ( and, by extension, depth of field) will vary depending on how large a circle of confusion you consider to be "acceptable". The less critical you are (or the s maller the print size you want to make), the larger a circle of confusion you ca n use in doing your DOF calculations.

Kodak does put out a publication on optical formulas which includes the "standar d" COC size for different film formats. (Sorry, I don't remember what they are) . However, there is no such thing as the "correct" circle of confusion for a gi ven lens--basically, its whatever you can live with.

Rob Rielly
12-Jan-1998, 14:09
Graflex put out a reference card to carry in your equipment case that lists the circle of confusion for the Graflex 135 Optar as 0.003". The card also has a de pth of field reference for various distances at each f stop. I'd be more than h appy to scan it and e-mail it to you, if that will be of use. Regards, Rob Riel ly