What does CI means?

[sweat100]

After reading some kodak webpages on films, there is a table on CI and some numbers there. What it measures? How can we manipulate it during development?

[photobum]

Originally Posted by sweat100 After reading some kodak webpages on films, there is a table on CI and some numbers there. What it measures? How can we manipulate it during development?

The term CI refers to Contrast Index. This abbreviation is commonly used in sensitometry or the science of determining the sensitivity of photographic materials.

When measuring prints certain paper manufacturers sets an approximate or estimated value. Example, Kodak says '0.58 is the contrast-index aim for printing negatives with a diffusion enlarger; use 0.43 if you will print negatives with a condenser enlarger.'

These values are not die-hard standards, but just references or starting points. There are variations from the paper, the enlarger, the enlarging lens, the light source, the developer we use, the temperature, agitation, etc.

There are several ways you can tweak the CI. Strength of developer, agitation, developing time, temperature, toning, etc are some of them.

By the way, newer lenses are generally better in contrast, so developing times should be coming down ever so slightly over time, as lenses on both ends of the system (the camera and the enlarger) improve.

My advise to you is ignore those numbers. Sensitometry is a never-ending science by itself. You don't want to go there. The last time I was there, I ended up plotting sheets and sheets of graphs. Concentrate on producing your art. Let the scientists at Kodak and Ilford worry about them. Don't step into the darkside of photography.

[sweat100]

I see... It was talking about contrast. I think i can jus tweak it with different grades of paper. May jus make my life easier.

[photobum]

Originally Posted by sweat100 I see... It was talking about contrast. I think i can jus tweak it with different grades of paper. May jus make my life easier.

Or just play with the filters if you use multigrade papers.