Narrow Band Enlarger Light Source With Graded Paper

Old-N-Feeble · Nov 22, 2018

Would a narrow band enlarger light source used with graded paper 'potentially' improve sharpness of lenses? The color would depend on whatever wavelength your lenses perform best plus the color sensitivity of the paper used, Perhaps it could make the purchase of pricey APO lenses completely unnecessary for monochrome printing on graded paper.

ic-racer · Nov 22, 2018

Projected B&W image should exceed paper resolution, unless you are doing something oddball or very big enlargements.

AgX · Nov 22, 2018

Your argument would have a stand if the ideal correction of a non-apo lens would be just on two wafelengths the light source would emitt and if at least one them was useful for exposing.
Or rather "some" stand as there still would be the issue of spherical abberation, which also is reduced by apo-lenses.

Nonetheless a interesting idea!

kevs · Nov 22, 2018

Old-N-Feeble said:
Would a narrow band enlarger light source used with graded paper 'potentially' improve sharpness of lenses? The color would depend on whatever wavelength your lenses perform best plus the color sensitivity of the paper used, Perhaps it could make the purchase of pricey APO lenses completely unnecessary for monochrome printing on graded paper.

I have a green-and-blue l.e.d. light source that could be called 'narrow-band'; the major benefit is that my negs never 'pop' due to heat, so I don't need to refocus the enlarger. I rarely print larger than 6" square, and I haven't noticed a change in sharpness since I switched over from incandescent, using an 80mm, 4-element Minolta lens.

Unless you're doing scientific work, or making monster enlargements, it seems likely to me that accurate focussing, flatness of negative, suppression of internal lens reflections, cleanliness of the lens, avoidance of diffraction, etc, would be more important in getting a sharp, contrasty print than worrying about the wavelength of light.

YMMV, of course.

jim10219 · Nov 23, 2018

You could test it. Just get a gel filter used for lights and place it in the filter holder above the negative (if you have one). Pick a color that works best with your paper. The lens doesn't care what color you use, so long as you focus it with the filter in place. It can focus any color of light with the same level of sharpness so long as you're limiting it to one color.

Personally, I don't think it would do much for you. To take advantage of that, you'd need to enlarge a image to the point of highly noticable grain, at which point, you've got other problems.

bernard_L · Nov 23, 2018

Chromatic aberration is just one among a number of optical aberrations: spherical aberration, astigmatism, coma, to name a few. So, adressing just chromatic aberration may not result in significant improvement. Plus, I seem to remember that APO, initially meaning corrected at three wavelengths, is often used generically to denote a lens with higher degree of correction of whatever aberration.

revdoc · Nov 23, 2018

Graded paper is already "colour blind" to some extent, being primarily sensitive mostly to blue, somewhat to green, and not much else. If your enlarger lens isn't properly achromatic over that short range, you need a better lens.

DREW WILEY · Nov 24, 2018

My Peak Critical Grain Magnifier came with an optional deep blue eyepiece filter. I've never installed it except once out of curiosity. Apparently there was an era when quite a few enlarging lenses were so-so and didn't "see" light quite the same way as typical graded papers. But I work almost exclusively with modern Apo enlarging lenses. And now it's predominantly an era of VC papers anyway.

Old-N-Feeble · Nov 25, 2018

Thanks for the replies, folks. I didn't know single grade papers have a narrow band of color sensitivity. I love learning new stuff.

Narrow Band Enlarger Light Source With Graded Paper

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