I focus the eye, but in the enlarger/print there is another focus... (a read B. Thornton)
What you are refering to is called the chemical focus and it was a problem when enlarging papers were only sensitive to the shorter wavelengths of the spectrum (violet and blue light). It is not a problem with film which is panchromatic in its response.
Last edited by Gerald C Koch; 09-23-2012 at 12:39 PM. Click to view previous post history.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.