I'm considering buying a (used) densitometer to try to get more objective feedback on my B&W exposure/processing, although I don't see myself going whole hog into sensitometry. I've read "The Negative" and a few other discussions of the issue, but I don't feel I have a complete grip on the strategy for using a densitometer. I'm curious how useful folks feel these are and whether a transmission densitometer is most of what you need or whether I should be looking for transmission/reflection machines.

-- Chris Patti (cmpatti@aol.com), August 03, 2000

Answers

I've just ordered a transmission densitometer and didn't feel the need to pay 50% more for one that could do reflectance as well. I can tell whether I like print values or not. The task of the densitometer is to give me objective data about negative values and how they will need to be handled for exposure and development of the print. I've never felt the need for this in silver printing, or in Pt/Pd printing at small sizes. But I'm working a lot with banquet cameras, and the coating and paper for a 12x20 palladium print comes in near the $10 mark, so I've finally decided that a densitometer might pay for itself in time and materials saved by better advance information. I still expect that the best it will give me is a "good first workprint" (not a small benefit) from which I will refine the final result.---Carl

-- Carl Weese (cweese@earthlink.net), August 03, 2000.

Before you buy something be sure to check for used equipment that may be available from labs going out of business, upgrading etc.

I find a densitomer to be very useful when trying new films, developers etc; with it I can usually find an EI and CI with just a couple of exposure-test strips, plus by examining curve shape I can easily tell if a combination is worth working with any further.

Of course these same things can easily be achieved by shooting, developing and printing a couple of short rolls of film.

Actually that's pretty much the way I went about it; I had a film and process that consistently gave me the desired results, so when I first got a densitometer I shot and developed a test strip, then read and plotted it. This gives me a standard with which everything else is compared. No high-end sensitometry here; my brain's not up to the strain.

My densitometer will also do reflection but I've never felt any need to work with that.

-- John Hicks (jbh@magicnet.net), August 04, 2000.

I use a densitometer for two purposes. First, I use it to determine my correct film speed as that ASA that will give me a Zone 1 which develops at 0.1 above film base and fog. Use the recommended development time, temperature, etc., to determine your ASA.

After determining my N (normal) development time, I will print each of the zones 1 through 9 (or 10) at normal N development. Then, I use a densitometer to determine the other development times.

For example, N-1 development time should take a Zone 8 exposure and print it at Zone 7. So, expose several sheets of film at Zone 8, and develop these for various times that are less than N normal development. For each of these sheets of film, plot a point on a graph with the densitometer reading on the vertical axis and the development time on the horizontal axis. Then interpolate from this graph the time that should give you a normal N Zone 7 negative. Recall that, since you developed each of the zones at normal N development, you know the densitometer reading of a Zone 7. You can adopt the same strategy for determining N+1 and N+2.

I find that an N-2 is best determined by varying the concentration, versus the development time. But, the interpolation process is the same.

As you become familiar with the paper that you use, you will know the correct densitometer readings that will give you a Zone 8 exposure, a Zone 7 exposure, a Zone 5 exposure, etc. So, for a new film, you can also use a densitometer to help determine your Normal N time, using the same interpolation process described above.

As a target, I use a frosted piece of glass with a daylight corrected tungston (blue) bulb behind it. (I forget the Kelvin, but it approximates daylight.) While it could also have been my technique, I tried using a regular tungston bulb, and got wrong values. In combination with your lens aperture, you can vary the distance between the bulb and the frosted glass to replicate the different zones.

-- neil poulsen (neil.fg@att.net), August 04, 2000.

I don't know where you are or what lab facilities you have near you, but have you tried contacting them to ask if they would consider letting you read values on their densitometer? I have been in the lab business for many years, and if anyone ever asked if they could read their tests I never hesitated in saying yes. Most good quality control people will help you in plotting your curves if that is what you need. You really are only concerned with transmission qualities unless you are running machine control strips on a paper processor. My recommendation would be to talk to your local lab people first and see if they will help you. I think that you will find that most will.

-- fred (fdeaton@hiwaay.net), August 04, 2000.

I use my denistometer whenever I try a new film/developer combination or when I am doing zone testing. It helps a lot. Mine does not have the reflection feature, but I don't feel a need for this.

-- William Marderness (wmarderness@hotmail.com), August 04, 2000.

I recently got a rather good deal on a used densitometer on eBay, but of course there are always risks with that route. It turned out well for me. You might also consider avoiding the purchase altogether, and still being able to measure densities. There is a recent article on how to measure densities using only your enlarger, and some printing paper. I do not have the reference with me now, but there is a link on my website www.vsta.com/~alrob which will give you the information.

Al Robinson

-- Al Robinson (alrob@vsta.com), November 22, 2000.

I've been looking into purchasing a used transmission densitomer and thought I might revive this thread.

Are there any guides to the different models? I see lots of them on eBay for not too much money, many from printing shops and medical labs that have closed down, but the sellers usually don't have too much info on them. I gather that the X-Rite 810 is popular for photographic purposes and I would expect most of the Macbeth types to be appropriate, but I have no idea about the differences between the TD401, 402, 409, etc. Do they all measure in the same units? Are there any to avoid? Any particular problems to look out for? Any physicians/radiologists out there who can comment on the ones marketed primarily for medical use?

-- David Goldfarb (dgoldfarb@barnard.edu), October 23, 2001.

Just for the record, I hunted around and got a good deal on an ancient Macbeth TD-102--a simple color transmission densitometer with a match needle readout. It isn't pretty, but it zeroes and seems to respond in a not unreasonable way on a few negatives that look good to my eye. Now I have a lot of reading and testing to do.

-- David Goldfarb (dgoldfarb@barnard.edu), November 13, 2001.