Changing Time vs Aperture When Making Enlargements?

[Thomas Bertilsson]

Nicholas,

Your test shows even gray density over a wide range from 1s to 256s, which is great news for Ilford users.

However, did you also test for contrast, to see if it was affected by exposure time?

Thanks.

- Thomas

My experiments show very little to no reciprocity failure with Ilford MGIV RC. I'm sure it holds for the rest of the Ilford range.

http://www.darkroomautomation.com/su...ermittency.pdf

As noted in the application note, the range of exposure times in the darkroom is very narrow - 4 seconds to 64 seconds is equivalent to changing the shutter speed on a camera from 1/4th to 1/60th of a second. NBD.

But unless you have some way of precisely measuring light and controlling exposure the whole reciprocity issue is moot.

For color you need to hold exposure time constant if you can.

When changing magnification the ((M + 1)/(m + 1))^2 formula works very, very well -- see the sticky thread at the top of this forum.

[Nicholas Lindan]

did you also [do a reciprocity] test for contrast, to see if it was affected by exposure time?

Not as part of that series. But you are right, I should add the results of a test for contrast to that application note.

[artonpaper]

Back in the 70s, I took George Tice's printing class at The New School. He had the best visual aids ever. He brought in a set of prints, I think were 11 x 14, and each print was printed of the same negative at every aperture on the lens. If my memory serves me they were from a 35 mm negative. I don't remember what lens he used, but I seem to recall he liked Schneider Componons. He always used a longer focal length than the recommended one. So for 35, he used an 80mm, for 2-1/4 he used 135mm, and for 4 x 5, he used 150mm. Of course he adjusted the exposure time by the equivalent of one stop. There was a noticeable loss of sharpness on the smallest apertures. That I remember well. Some loss of edge sharpness when wide open. There was very little difference in print density, minimal really. I do not recall what paper he used, but in those days Agfa Brovira was a favorite of his, although he used a host of different papers. I always avoid the smallest apertures and I use ND filters under the lens when exposure time become too short.