Circle of confusion : LUSENET : Large format photography : One Thread

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

-- Terry Lorch (, January 11, 1998


The circle of confusion is not a property of the lens itself. Rather, it is a measure 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 smaller the print size you want to make), the larger a circle of confusion you can use in doing your DOF calculations.

Kodak does put out a publication on optical formulas which includes the "standard" 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 given lens--basically, its whatever you can live with.

-- Rob Rothman (, January 12, 1998.

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 depth of field reference for various distances at each f stop. I'd be more than happy to scan it and e-mail it to you, if that will be of use. Regards, Rob Rielly

-- Rob Rielly (, January 12, 1998.

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