You are well equipped on the development and densitometry side. While you haven't mentioned it, how will you expose the film? One of the most difficult tasks for me is obtaining an evenly lit test target that retains it's lighting levels with great consistency. I finally resorted to making a "rim light" arrangement with 4 - 100 watt Reveal bulbs (a higher color temp than regular bulbs.) I mounted these in the four corners of a board that has a hole in the center through which I can shoot. This has removed the evenness variable and the change in intensity of these bulbs over their life is not a factor during the relatively short duration of a film testing session.
Even though the Reveal bulbs are not a full daylight color temp (~5600+k), they seem to be close enough where I can see no difference in film response in daylight and even full-shadow - blue sky conditions (9000k ++.)
Pay close attention to the response you get from TMax. With your obvious interest in development control, I think you will find this film to be loaded with potential and a good match for meticulous personality.
My experience is somewhat difference. I find that if I follow closely all of the details involved in Davis' BTZS method of testing, the data from my files is remarkably close to the data in his samples for any specific combination of film/developer.
Originally Posted by Jorge
Likewise, I fully expect that if someone takes my own data and repeats the conditions of the test they should come up with results very similar to my own. There are many reasons why one might not come up with the same results, but with very close control of the materials and the testing conditions there should not be much difference in results.
Originally Posted by blaughn
Steve is using a sensitometer. That is his exposing system.
There are many reasons why results can vary, a uncalibrated thermometer, water quality variations and composition, rotation speed and developer oxidation, etc. Not everbody has consistent temperature control or access to destilled water, and even so, I have rarely seen destilled water that is all uniformely 18 Mmhos resistance, so even within treated water there are variations.
Originally Posted by sanking
Why tests if what you are aiming too is "not much difference?"
In any case, your experience is different than mine, lets leave it at that. OTOH I would rather grow and become a better photographer by spending the 2 or 3 years making photographs than step wedges, but to each his or her own. If Steve wants to spend all this time, money and effort to do this, that is his choice, I just dont see the usefulness when there are sites like digitaltruth that have a lot of this information already. As to edge effects, sharpness, etc. This once again is IMO relative to the tester and his results. Didn't you and some other guys in this forum had a thread on edge effects that went on forever and you all never agreed?
IMO testing should not be the end goal but a stepping stone to better photography, but hey, I am not doing it....so have at it..
Don't worry about film/developer combos at this point - you need to come up with a written Standard Operating Procedure for this before you do any testing. Then let us read it and ask opinions then.
Originally Posted by magic823
So I would suggest that you write out your proposed testing procedures - step by step of each method. Be as precise in describing step of each method. And by doing this, you will have hopefully eliminated some of the possible variables that you may run into. This is really the only way we can help you figure out if you have come up with a suitable method of testing.
I realize that you are being very general in your post above, but as an example of amibiguity - are you really going to process each film at it's N-1, N, and N+1 contrasts? Or are you going to generate a family of film curves that are based on standardized times to determine the times for N-1, N, and N+1? Is N-1 and N+1 enough? Perhaps you should also include N-2 or 3 or N+2 and 3?
So will you start out processing a given film/dev/agitation combo at 5, 7, 10, 14, and 20 minutes at a particular temp (and which temp - and why did you choose that temp?) to build a curve family. Then you crunch some numbers - and then you find out that N-1 = 7.8 min, N=9.4 min, and N+1 = 12.1 min (as an example). So then are you going to go back and then do a runs at 7.8, 9.4, and 12.1 minutes to verify your calculated times?
And if you do those 3 (or more) verification runs - how close is close? If you pick your CI of N to be 0.58 (side note: what where the reasons for picking that value?), is a CI of 0.55 good enough? Or is 0.57 good enough? What about 0.61 or 0.59? Or do you need to get 0.58 for your tests?
And then do you go back at a later date (days or weeks later) and then verify that you can get a CI of 0.58 with your time of 9.4 minutes using that same film/dev/agitiation/temp combo? You probably should try to to build some certainty into your testing scheme.
What about things like do you start the development time when you start to pour the developer into the tank or when you have added the last drop? I feel that one way is better than the other.
How about things like what density will the film be that you use to measure the graininess and take your microphotographs? What are the targets you are going to be using to measuring edge effects. How much difference in exposure are you going to use to test the difference there is between edges? How are you going to measure them?
Do you have calibrated equipment - densitometers, sensitometers, timers, thermometers? How recent was the calibration? How accurate are your measurements?
These are just a few of the kinds of questions that you need to have answered before you start a project this big. Especially if you don't want to spend a lot of time and resources redoing stuff because you are getting data that is conflicting or just not making any sense.
It may seem like a big undertaking to write all this out - but you will be soooo happy that you did when you finish the project. And if you do write this all out before testing - you will already have the first several chapters of your book written!
Finally, I would like to offer my thoughts and opinions on any testing Standard Operating Procedure that you come up with if you like.
Kirk - www.keyesphoto.com
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BTW, to speed you up a bit check out http://www.flickr.com/groups/bw_film-dev_combinations/
but be aware that ANY scanned image on the internet is only a hint in the direction of what the prints and negs will REALLY look like