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#21
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The difference in enlarging lenses
Bob Salomon wrote:
Or 50mm 2.8 Apo Rodagon-N? No. It was the "old" Apo-Rodagon without suffix. However, I had both the latest Apo-Rodagon "N" in 2.8/50 and 4/90 on loan here and compared them to my "old" Apo-Rodagons with the same focal length. With a carefully aligned enlarger, no differences visible, tested at 2x, 6x, 10x and 15x enlargement (90mm) and 4x, 8x, 12x, 20x (50mm). So I decided to keep my old glass. All my enlarging lenses are used at two f-stops down from full open. In a glass negative carrier as the lenses are designed to be used with? Of course. I use my Durst G139 with TRINEG glass carrier and use a Versalab Parallel laser alignment tool to align easel, lens board and carrier. Martin |
#22
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The difference in enlarging lenses
Patrick Gainer wrote
Not true. The focus can only be compensated for one wavelength. The prism in binoculars affects the chromatic aberration of the system and is accounted for in the design. "...one wavelength." Good reason to scrape the blue and green sensitive VC papers. For this purely academic discussion of negative carriers I will inject for consideration the quantum nature of light. That nature is most obvious when using a diffusion head. The light emerging from the glass side surface of the emulsion is also diffused. It should be considered for it's quantum as well as it's wave nature. Do the analysis one ray, one quanta, one photon at a time. Dan |
#23
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The difference in enlarging lenses
I think the main problem with glass type holders is dust.
That is controlable but takes some effort. Generally speaking, I think most glass negative carriers should be used as a liquid gate holder rather then just dry. Thus no dust problem. Larry |
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