Monday, May 13, 2013

Large Format Fun

I had to walk over (and through) a neighborhood high school campus in order to pick up my youngest son from lacrosse practice. Generally, I would just walk through the buildings and yards without really thinking much about the 'scenery', but that day, the sun was nearing twilight and things were getting 'golden' and shadows were lengthening. So I decided to bring along my Speed Graphic with a couple of sheets of Tri-X 400. I am still just sort of exploring this camera and how to capture on film the images that I see in my head. After walking around a while, I decided on this chain link fence with some padlocks on it.


I had my Graflex Optar f/4.5 lens on the camera, but it was still a little bright out for that wide aperture on 400 speed film. I stopped down to f/8 which gave me a reasonable shutter speed (using the rear focal plane shutter) and I thought it would still be a nice depth of field for this receding subject. I find that I still tend to think in 35mm terms when it comes to DOF and focal lengths. It is hard to wipe out those habitual patterns that have been ingrained for so long. What I found was that the DOF was much less than I was expecting. This is because of the wonderful physics of optics. Without getting into Circle of Confusion and other technical details that you can read elsewhere, I will just make this comparison:

For a 35mm negative, using a 50mm (normal) lens at f/8, the Depth of Field is about 8 inches.
For a 4x5" negative, using a 135mm (normal) lens at f/8, the Depth of Field is about 4.5 inches.

Spend some time reading up on COC and DOF and get a good understanding of what your lens is doing. It will increase your enjoyment of photography and will get the images on the film looking more like what is in your head.

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