</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (David A. Goldfarb @ Feb 5 2003, 02:19 PM)</td></tr><tr><td id='QUOTE'>
My theory on this is that VC papers have a wider spectral response than graded papers (otherwise the filtration wouldn&#39;t work), so they will show up chromatic aberration in the lens more than graded papers, depending on the filtration, the lens, and the light source.&nbsp; If you use an apochromatic lens or a narrower band light source or a strong monochromatic filter, you shouldn&#39;t have a serious problem with chromatic aberration, so you might not notice a difference under those circumstances.</td></tr></table><span class='postcolor'>
Chromatic abberation as an error in a lens system affects black and white media nearly equally as severly as color media.

The Spectral sensitivity of "Graded" (non-variable contrast) paper is not restricted to a narrow spectral band ... and few enlarger light sources (actually, none that I know of ) are to any great degree monochromatic. Chromatic abberation is caused by a lens design that focuses different wavelengths of light to converge to differing points ... and the worst case of that I ever encountered was in a Kodak Contour Projector - where the edge of a silhoette projected to the exteremes of its 30" screen were red on one side and blue on the other. Another Comparator manufacturer (Jones and Lamson) offered a monochromatic light source - a mercury vapor lamp - to avoid just that effect.

Enlarging lenses -- every one that I&#39;ve ever been in contact with - seem to have *very* little chromatic abberation - as a design criteria.


a defect