Originally posted by mrpink ....
Please tell me what determining parameter (and value) do I look for in a macro lens, (or how do I calculate the value needed) when I have an object that is 1mm in size that needs to be full screen......
For a full screen width of 1mm on a K-7 you need an optical magnification of 24X. There are no out-of-the-box 24X macro lenses.
As others have pointed out, you probably will be happy with less than this as you can crop.
A reversed lens setup with focusing rings set at infinity will give a magnification of :
magnification_minimum = prime_lens_focal_length/reversed_lens_focal_lengths
As the focusing ring on the primary lens is turned, the magnification will increase by:
magnification_increase=(primary_lens_extension/Primary_lens_focal_length)(1+minimum_magnification)
so for a 300mm primary lens and 28mm reversed lens:
minimum_magnification=300/28=10.7X
If turning the 300mm lens focusing ring extends it by 30mm the magnification will increase by:
magnification_increase = (30/300)(1+10.7)=1.17X
So if you *really* want a magnification of 24X you'll need to use a 300mm and reversed 12.5 mm lens or maybe add a close-up lens to the stack. It'll be hard to handle, but possible I think.