----- Original Message ----- From: "Uptown Gallery" <[email protected]>
> Or do we all just > develop a realtionship with a particular camera from experience? Some of that is desirable of course. > With my 35 mm pinhole, I used the meter on the converted camera, and > pre-viewed my composition thru another SLR with the zoom set to approximate > the f.l. of the 35 mm pinhole camera. I'm just not confortable 'blindly' > pointing and shooting and hoping I'm not too close, not too far. That's a good method. If you are using an SLR and the pinhole is mounted on a camera body cap, you don't need a second SLR. Just mount the camera on a tripod, compose with your glass lens a expose with your pinhole one. > Can an analogy be drawn between a 'normal' perspective focal length on two > different formats? Say, a 50 mm f.l. lens on a 35 mm camera is about the > same (whatever same means) as an 85 mm lens on a 120 / 2-1/4" camera. Yes, you can find that analogue lens based on image circle, in other words, based on finding the focal length that would give you similar angle of view for the diagonal of your format. Or, you can do it by finding the focal length that'd give you similar horizontal or vertical angle of view (that "or" is exclusive). This latter method is technically speaking "less accurate" when comparing formats having different ratios width/length. The above involves some math, more on that upon request. In your example, a 50mm lens on a 35mm format compared to 2 1/4" square format (6x6), the analogue lens based on image circle would be 98mm. Based on horizontal (landscape) angle of view it'd be 83mm and finally, based on vertical angle of view 125mm. > I saw a pinhole camera on the Internet somewhere (Australia?) that had a > wireframe 'viewfinder' on top and side. I guessed the manufacturer figured > out how big to make the rectangular 'viewfinders' by trial and error. No need for trial an error when geometry would tell you that for a simple viewfinder, the rectangle should be exactly the same as the format size and the "eye let" (is this what it is called?) should be exactly one focal length distance from the rectangle. Guillermo
