Contrast vs. density: what is the difference?
Posted: Sat Aug 08, 2009 6:25 pm
Can anyone explain what the difference between contrast and density is? I know pushing increases density rather than contrast, but what does this mean?
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Pushing does NOT increase density, only contrast! Density refers to the "blocking power" of the negative, i.e., how much light it blocks compared to nothing. Contrast refers to the difference between the thinnest and densest areas of the negative. Increasing exposure tends to increase density overall; increasing development tends to increase density in the denser areas only. That is why pushing does not work.kcf wrote:Can anyone explain what the difference between contrast and density is? I know pushing increases density rather than contrast, but what does this mean?
I was out yesterday shooting up a roll of Konica Infrared that expired in 2005. It was the last of the rolls I bought a few years ago when I heard that it had been discontinued. I have a 9 more rolls that I bought off of eBay in the spring, but that's immaterial other than to make the point that I'm really careful with this film. Each frame is prescious. Needless to say, I made a mistake when exposing it yesterday. I used a red 29 filter insteaad of my usual red 25. There is a 1 stop difference between the two. I forgot to calculate that in. I decided to push process. I used PMK Pyro because it has a compensating effect, which retards the highlights while bringing out the shadows. I increased development time by 50%, and hoped for the best. When I removed the film from the developing reel, I laughed like a mad scientist. The negatives were perfect. The results can be seen on my Flickr page: St John's Bridge numbers 3, 4, and 5. Sometimes push processing does indeed work.Ornello wrote: Pushing does NOT increase density, only contrast! Density refers to the "blocking power" of the negative, i.e., how much light it blocks compared to nothing. Contrast refers to the difference between the thinnest and densest areas of the negative. Increasing exposure tends to increase density overall; increasing development tends to increase density in the denser areas only. That is why pushing does not work.