Densitometer readings of slides & negs for scansgreenspun.com : LUSENET : Advanced Photography : One Thread
Does anyone have a set of densitometer readings from shadow to highlight of the same or very similar images shot on Chromes and Neg film. I am interested in a direct comparison as I keep hearing that neg film "has a greater range" yet when we scan the chromes end up with a greater range on high end scans.
-- Dan Smith (firstname.lastname@example.org), November 14, 1999
What you request is sensitometric testing. "What is the film density output for equal gray scale step input?" The simplest thing is to look at the characteristic curves of the films you are interested in. They can be found at www.kodak.com, and I suppose at Fuji's site as well. For negative films, you have high d-min, and relatively low d-max. Negative film can handle a larger input range of light levels, but outputs a smaller range of densities on the negative (low contrast). On the other hand, transparency/chrome/slide films have very low d-min (bright whites), very high d-max (dark blacks), and high contrast, which takes in a narrower range of light, and outputs a larger range of densities. When you look at the characterisitic curves, note the x-axis scale, which is likely for neg film to be 4 log-exposure units, while slide film will be 3 log-exposure. Be careful if trying to overlay the curves, because scaling is different. Slope of the straight(est) portion of the curves is the contrast.
-- Dan Sapper (email@example.com), November 16, 1999.
I believe Dan posted this question after exchanging some e-mails with me last weekend, where I was trying to explain why slide films yield better scans than negative films. Dan Sapper's explanation helps clarify my suspicions, the greater difference between d-min and d-max on slides will give you a better scan, assuming you have a scanner (such as the Heidelberg Tango) capable of pulling out that range. Consumer grade scanners' inability to record this range is probably what leads to all the confusion with people believing negative films scan as well as slide films.
Another consideration (while I'm off on my tangent) is the difference in sharpness between color negative and slide films. They dye clouds on C-41 process film tend to scatter the light when you are scanning, and thus yield a less sharp image in the scanned file. I can easily discern the difference on my monitor. The proof will come when I send the files to a LightJet 5000.
For what it's worth, I scanned some black-and-white negatives (T-Max 100 and Ilford HP5 Plus) last weekend too, and the results are stunning on screen. I can hardly wait to start testing my quad-tone inks and see the results.
-- Darron Spohn (firstname.lastname@example.org), November 16, 1999.