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| Enlarging Lens - What Distance for Optimal Image? |
UsuffOmar |
05/01/05 |
I am photographing objects at close distances, around half a metre away, with both a 35mm and medium format camera. Rather than fitting standard macro lenses to the camera, I am using enlarging lenses designed for use with an enlarger. (Good quality ones sometimes go cheap on eBay.) The distance “S” from the camera’s focal plane to the enlarger lens seems critical to a sharp image. (I have a diagram of the set up at http://www.geocities.com/usuff_omar/Lens_Question.htm.)
From simple observations I’m estimating that the best image quality is obtained for 50mm, 80mm and 105mm focal lengths of enlarger lens when the distance from the focal plane to the enlarger lens is about approximately 6cm, 9cm and 11½cm respectively. At longer distances the image quality can deteriorate. These measurements are a guess on my part.
Is there any formula I can use to find the value of “S” (focal plane to enlarger lens distance) and “D” (focal plane to object distance) for optimal image quality? Also, from where do I measure “S” on the enlarger lens. Is it from the camera’s focal plane to the nearest tip of the lens barrel, or to the middle of the lens somewhere or to the furthest end of the lens?
Many thanks. |
Clarification/Follow-up by UsuffOmar on 08/03/05 1:34 pm:
Thanks, Katiy. I've since found the answer. The object to lens and lens to focal plane distance is governed by the "thin lens" equation of 1/F = 1/S1 + 1/S2. Now I use my calculator instead of my ruler.
Clarification/Follow-up by katiy on 08/04/05 2:23 am:
What are you taking pictures of so close up. I like the macro lens. It's fun taking close pictures if they turn out. Clarification/Follow-up by UsuffOmar on 08/04/05 1:25 pm:
I'm taking pictures of the movement of a pendulum. See www.bpresent.com I create patterns from movement.
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