Lens Angle of Coverage calculator

[Jack Flesher]

I am sure this has been done many times before, and I thought I saw it somewhere online some time ago, but I could not find one so I built one.

If anybody wants to build their own, here is the formula for Excel. Given both the lens focal length in mm (or inches) and angle of coverage in degrees, it will calculate the lens' total available Image Circle in mm (or inches).

Formula for the Image Circle cell is: =2*(TAN((ENTRY CELL LOCATION FOR INPUT OF LENS' ANGLE OF COVERAGE/2)*PI()/180))*ENTRY CELL LOCATION FOR INPUT OF LENS' FOCAL LENGTH.

Example. In my spreadsheet, cell D7 is where I input the lens angle of coverage and B7 is where I input the lens focal length, and the formula is this: =2*(TAN((D7/2)*PI()/180))*B7

Mods: If this is redundant or old news, please feel free to delete it.

Cheers,

[Ash]

Brilliant, thanks!

I was thinking the other day whether I could nab the calculation and sort all my lenses into a spreadsheet

Oops, then I re-read and wonder, how do I find out angle of coverage?? *embarassed expression* !

[Gordon Moat]

Would that only work for one aperture? The reason I ask is that in Schneider lens specification (probably in other companies too), the coverage is different for wide open, and (for example) f22.0. That implies that the coverage angle changes with aperture.

Ciao!

Gordon Moat
A G Studio

[Jack Flesher]

Hi Gordon:

Absolutely, a lens' angle of coverage changes with aperture. Most manufacturers will spec the angle of coverage with a specific aperture, usually f22 and sometimes f16 or f32 for large format lenses, and some manufacturers will also include the spec for wide open.

The spreadsheet requires you to input angle of coverage, so depending on what value you enter, you will get different output values. In this fashion, assuming you had the AoC spec for each aperture of a given lens, you could conceivably generate a table of IC's for each aperture using the formula.

Cheers,

[Jack Flesher]

Oops, then I re-read and wonder, how do I find out angle of coverage?? *embarassed expression* !

It's often spec'd by the manufacturer for a given family of lenses...

[Ash]

Ah, no joy for me then; I wanted to work it out for my two Goerz lenses (Dagor, Dogmar) a Ross Xpres, an un-named brass barrel lens, Cooke Process and Aviar lenses, and a few other pieces like the Hanimex 300mm slr front cell.

[Jason Greenberg Motamedi]

There is a nice web based calculator at Chad Jarvis's site:

http://chadjarvis.com/aoc.html

[Ash]

Thanks Jason!

[Jack Flesher]

There is a nice web based calculator at Chad Jarvis's site:

http://chadjarvis.com/aoc.html

That's the one I was looking for

[Jason Greenberg Motamedi]

Thanks Jason!

Ah, don't thank me, thank Chad. He used to hang about here, does he still?

jason