The Great Sensitometer Shootout....

ic-racer · Oct 15, 2012

Rafal Lukawiecki said:
How do you control the exposure of your ESECO Speedlight SL-2, if I may ask? I was hoping to use it with both 400 and 100 film, and it would be great if I could get the entire set of steps, except for the first one or two, exposed enough to read a density above fb+f. Do you use filters, multiple exposures, or a modification of some sort?

There is a trimmer resistor for each color. The two units I'm using came 'factory calibrated' and I don't see a good way to set the trimmer back after changing it, so I have not altered these units.

There is some extra density material over the LEDS that could be removed to move the step wedge exposures when exposing slower film.

ic-racer · Oct 15, 2012

Forgot to say that Jeff Bannow has kindly donated the two Speedlight SL-2 units for the test.

Stephen Benskin · Oct 15, 2012

I don't know if anyone has heard of the Gamma-Lambda effect. I did a little research into this sometime ago. Average gradient is affected by the wavelength of light. Blue light tends to decrease the gradient while green tends to increase the film gradient. Red and white light tends to fall somewhere in between. My tests confirmed this. I tested nine films using tri-color filters with my EG&G. Hold times were identical and the film was processed together in a dip & dunk. The differences weren't great but there were differences.

This is an example from the those tests.

Photo Engineer · Oct 15, 2012

Stephen;

I have mentioned this before.

PE

Stephen Benskin · Oct 15, 2012

Sorry, I didn't know you've already referenced my paper.

ic-racer · Oct 16, 2012

Stephen Benskin said:
I don't know if anyone has heard of the Gamma-Lambda effect. I did a little research into this sometime ago. Average gradient is affected by the wavelength of light. Blue light tends to decrease the gradient while green tends to increase the film gradient. Red and white light tends to fall somewhere in between. My tests confirmed this. I tested nine films using tri-color filters with my EG&G. Hold times were identical and the film was processed together in a dip & dunk. The differences weren't great but there were differences.

This is an example from the those tests.

View attachment 58487

That effect was not tested here.

Photo Engineer · Oct 16, 2012

Stephen;

I made a post that described the effect of illuminant on film response as a function of wavelength. This is exactly what you describe and is well known in the industry. I did not reference your paper. I was using facts from my own background.

This is a general problem when one uses a narrow band illuminant to test a film or paper. It gives results that vary as much as you show in your graph or even more.

This error can lead one quite far astray.

PE

Stephen Benskin · Oct 16, 2012

Ron, my snarky response was meant to point out that I was presenting additional information to the discussing and even if it was no more than to re-emphasis a point someone has made previously, I don't feel anyone has the right to discourage discourse.

As for the issue of the importance of the wavelength of the illuminance, I could agree with you more.

Photo Engineer · Oct 16, 2012

Stephen;

The graph you offer, as I noted above is an excellent emphasis of this point. It is very important, as a picture is worth 1000 words. Right?

PE

ic-racer · Oct 16, 2012

Final speed test comparison.

This graph shows that the measured speed difference between Tri-X and FP4 was about the same percentage (arithmetic speed, not DIN), irrespective of sensitometer's type of light, intensity, color or duration.

Graph label text "ISO" is to indicate these are percentages of "arithmetic" speed and does not imply the tests were done under strict ISO conditions.

ic-racer · Oct 16, 2012

I have not used FP4 for many years, but this shows me that I can expose it in my camera with about 45% less exposure than what I have been using for Tri-X and expect to get good results. So, for me that would be an exposure index of 90 based on prior in-camera testing and establishing a personal exposure index of 200 for Tri-X.

ic-racer · Oct 17, 2012

There was a small error in the previously posted graph of "Normalized Change in Contrast Following 2 Minute Reduction in Development Time. This one is corrected.

ic-racer · Oct 21, 2012

I tried editing the second graph on post #6 in Photobucket, now the image gives an error when I try to retrieve it. This is a repost of the image. It is very small, so I'll have to re-do the entire graph.

Dismayed · Oct 21, 2012

So what densitometer should I buy for B&W film testing?

ic-racer · Oct 21, 2012

Dismayed said:
So what densitometer should I buy for B&W film testing?

For the two tests mentioned here, it does not matter they all work equally well. I might go for the LED one, but really whatever you can get for less than $100. Even an enlarger will work. These ESECO units list for $750 but we got them for $25 on ebay.

For "Beyond The Zone System" testing; I don't know. You have to buy into that system and it involves (from what I gather) matching paper to negative with the curves. I'm not a fan of that method of working but that is not to say it is not a good system or that people should not use it. I have used multigrade paper and variable filtration since 1974 and prefer working the negatives up as I print them with trial and error. Also, I don't have the workbooks or software for the system, so I can't test it with these sensitometers.

If I were to take a guess, I'd say that none of these units will work with that system because some of your photographs will be at exposures longer than 1 second or shorter than 1/1000 second. None of these 4 units duplicates how your film in your camera responds to daylight scenes one might photograph. Again, that is just my guess and someone should test how that system responds to different sensitometers. Of course the reflection densitometers used for reading the paper will be a whole other can of worms. I don't own a reflection densitometer and have turned them down when offered to me for free. I don't think they are very reliable at reading the glossy photographic papers I use. They are designed for the graphic arts industry.

Mr Bill · Oct 22, 2012

ic-racer said:
Of course the reflection densitometers used for reading the paper will be a whole other can of worms. I don't own a reflection densitometer and have turned them down when offered to me for free. I don't think they are very reliable at reading the glossy photographic papers I use. They are designed for the graphic arts industry.

Actually, a great number of reflection densitometers were made specifically for photo papers. Remember, every processing lab that used standard "process control" methods had to do this for both film AND paper. I can assure you that older machines, at least Macbeth and X-rite, did a fine job on photo paper, glossy or otherwise. I think there is just less need for these things, with respect to a regular photographer (as opposed to a lab operator, or researcher, or the like).

Rafal Lukawiecki · Oct 22, 2012

I only have a short experience of using a densitometer, but, so far, I found the Heiland TRD-2 to be very repeatable for both negative transmission, and glossy fibre paper reflection measurement, usually within 0.01 and never more than 0.02 spread.

ic-racer · Oct 22, 2012

Let me be rephrase my comment. Too many variables affect photographic paper's D-max to make reflection sensitometery reliable in choosing the contrast level of a printing paper in my darkroom.

I did not mean to indicate the instrument was mechanically unreliable, but the results cannot be relied on to give useful information in my printing technique.

Ok, try this. Make a test strip that goes to maximum black on the paper but keep blasting it with additional strips of exposure. Lay the processed and dried paper on an opaque surface and check for the darkest strip, now hold it up to the light. You can now see all those darker bands. So, even how you hold a print to view it influences D-max. Let alone effects of toning, print drying technique, angle of viewing, etc. To rely on reflection sensitometer results for choosing paper grade, all that has to be taken into account. I'm not saying that all can't be done. Just that I use my eyes to zero in on the correct exposure and filtration when making a print.

Photo Engineer · Oct 22, 2012

Reflection densitometry is an exact science. The mid scale variations are a measure of contrast, not the Dmax. Dmax is limited by the laws of physics causing it to fall between 1.8 and 2.2 depending on surface. In normal viewing conditions, this range can be seen, but anything over that, visible by transmission, is not seen by reflected light. This goes for color or B&W. However, again due to the laws of physics, in color there is a slight hue shift past the reflection cutoff limit.

So, you can trust reflection readings with most any good densitometer. At EK in KRL, we used Macbeth units.

PE

DREW WILEY · Oct 22, 2012

Looks like a fun project, but I certainly wouldn't try to extrpolate the results over different kinds of
b&w films, which in instances can be siginificantly affected by the color of light. Another problem is
that old-school bulbs for spectrophotometers and gear like this were actually "broken in" by burning
a number of hours before sale in order to reach a plateau of lumen and spectral output. The you were supposed to keep track of the number of hours of use for when to replace them, and not when
they actually burnt out.

Mr Bill · Oct 22, 2012

ic-racer said:
I did not mean to indicate the instrument was mechanically unreliable, but the results cannot be relied on to give useful information in my printing technique.

That's sort of what I meant when I said, "I think there is just less need for these things [reflection densitometer], with respect to a regular photographer." You're just not finding a practical use for it.

The situation might change if, for example, you found that you preferred the "look" of one paper to another, and wanted to study it to find out why. Maybe it's due to a subtle difference in mid-tone curve shape, which you could discover through sensitometry. On the other hand, the person I call the "regular photographer" might just say, "I like this paper better; I don't really care why, but this is the paper I'm going to use."

For myself, I've found reflection densitometers very useful in doing technical work for a large user (industrial scale) of photo materials. For myself as a regular photographer, not so much use.

ic-racer · Oct 22, 2012

DREW WILEY said:
Looks like a fun project, but I certainly wouldn't try to extrpolate the results over different kinds of
b&w films, which in instances can be siginificantly affected by the color of light.

Examples? There are not that many B&W films around. In 8x10 at lest.

DREW WILEY · Oct 22, 2012

Reflection densitometers are more likely to be used for process control in color work, whether monitoring chemistry or tinkering with alt processes, etc. Also needed in traditional graphics work.
I doubt the average silver darkroom would have much use for one. However, I use a transmission
densitomer as well as a projection densitometer a great deal.

ic-racer · Oct 22, 2012

DREW WILEY said:
different kinds of
b&w films, which in instances can be siginificantly affected by the color of light. .

Which one would you like me to try? If the spectrum response is too weirdo then it may not be good for much. X-ray films are pretty weirdo in the respons but would be perfectly suited to the colored LEDs.

DREW WILEY · Oct 22, 2012

Try TMX. I already know what to expect - I doubt you'll do several months testing on it like I did,
including batch consistency. It's fairly unique in certain respects, but it would be interesting to see
if you land upon it with your particular vintage of gear. Regardless of the outcome, these kinds of
gadgets are fun to learn about.

The Great Sensitometer Shootout....

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