Aperture & Focal Length comparisons

[Ken Nadvornick]

Maybe so, yes. This is a peripheral calculator that I threw into a larger flash-to-subject distance table printing utility because it might sometimes become handy.

That utility has become a bit of a Swiss Army knife sort of a thing. All kinds of stuff in there. But quite useful to me with Graflexes and flashbulbs and such.

For the purposes of subject flash distances and flash coverages and most everything else the nominal gate sizes would be just fine. But that would violate the software principle of getting it exactly right over and over without any additional effort on the part of the user, once I had those measurements.

I'm also considering adding a custom format option so the user can define whatever format they like. That could account for the variable gate sizes, if one wanted true perfection.

(Adding this little calculator is what I've been doing while sitting each Sunday and watching the Seattle Seahawks sink further and further into oblivion...)



[Edit: OTOH, shouldn't the more modern film format gate sizes all be defined somewhere as an ISO standard, or something?]

Ken

 

[John Koehrer]

Depth of field depends on the diameter of the aperture, not the f/stop, so longer lenses have shallower depth of field for a given f/stop because the aperture is bigger. For example, at 50mm, f/4 has a diameter (as seen from the front lens element) of 12.5mm. At a focal length of 100mm, the aperture diameter at f/4 is now 25mm, resulting in depth of field being shallower with the 100mm lens than with the 50mm lens.

A number of other replies suggest that that the f numbers influence DOF. The above is correct. The physical aperture rules.

 

[film_man]

That's what I was wondering about.. so will the depth of field at f4 or f8.0 in 6x7 be more like f2 or f4 in 35mm??? :confused:

The *practical* reality is about 2-2.5 stop difference between 135 and 6x7. It will never look the same because the picture ratio, tonality and contrast on 6x7 is different but for practical reasons this is roughly what it works out to. So if you are used to say "I need f/4 to get everything in focus in this kind of shot with my digi/135 camera and a 50mm lens" then you should be thinking "I need f/8-11 to get everything in focus in this kind of shot with my RZ67 and 110mm lens".