I asked the same question on photo.net then I figured it belongs here.
I recently got my first 8x10 and I was thinking about trying some high magnifica tion macro work with it. And then I read the optics article on photo.net and I m ade some calculations and ended up with a surprising result. It seems that when shooting 3d objects (that require some dof) there is virtually no reason to shoo t larger format since it yelds pretty much the same result.
First, here is the assumption : We are planning to photograph an object that is 24x24 mm in size and we want it to fill the frame. So with a 35mm camera we woul d have 1:1 magnification. With an 8x10 camera we would need ~ 8:1 (I would use a 65mm lens so I'd have enough bellows). The required DOF for this application is 2mm.
Using the formulas in the optics page a got the following numbers : 1. The optim um aperture for 35mm work came to f19 (optimum meaning the smallest circle of co nfusion due to dof and diffraction). For this f number the circle of confusion i s 0.026. So the number of "pixels" of the image would be 24/.026 = 923
2. For the 8x10 camera the optimum aperture is ~ f64. When the circle of confusi on is 0.093 So the number of "pixels" of the image would be 2.56 * 8/.093 = 2202 .
Important, the purpose of the exercise was to see if shooting 8x10 instead of 35 mm in the above conditions would dramatically increase the detail captured on fi lm (like I thought considering the huge difference in the film size). It looks l ike shooting 8x10 only about doubles the detail that a 35mm can capture. I am aw are of the advantage of eliminating another optic system by making contact print s and presumably the wider tonal range the LF can provide (I'm not yet conviced about that though).
So, the question is, is my conclusion anywhere near the results obtained in prac tice? Again, I am ONLY talking about macro work where dof is required, not flat work.
Bookmarks