Printable View
I borrowed a Macbeth densitometer. The manual says its possible to measure densi ty, but its a reflection densitometer. Is it possible to read my negs? My thinki ng is that I put my negs on a light-box and then meter the light trough the nega tives. Is this possible? And has anyone experience with this particular densitom eter. Its a portable reflection densitometer Macbeth RD 1145, of the Kollmorgen Instruments corporation.
Reflection densitometers are designed to read densities from the surfaces of paper. I would be highly suspecious of any negative readings you may get with your light-box set up. Very simple, what you need is a transmission densitometer. No other way to get around it as it is the right tool for accurate results. I have seen others use an inexpensive density wheel from companies like Kodak for approximate negative density analysis. Another thing I have found useful. Shoot your test shots for density through diffusion materials like those offered through Zonesystem.com for consistent readings. Very inexpensive and you can use it as a pre-exposure device. Good Luck
As mentioned above, I would be suspicious of the readings. Reflection densitometers include a light source that shines on the paper and the cell measures the light reflectde back from the sample. Which means what you will be measuring through a setup with the light table will include 1) light from the light table (some of which has been stopped by the opacity of the negative) AND 2) light from the densitometer source reflected back by the negative. There is no way to tell a priori how much has come from the light table alone (because any density will both stop light from the light table and simultaneously change the amount of light that is reflected back) i.e., any reading will be confounded. If you are determined to go this route, I guess you could try some calibration exercises, but the game doesn't seem worth the candle, IMHO. Cheers, DJ.