Help with my TMAX100 film test
I have been following the methodology listed in the howto articles for sandwiching a stouffer wedge card over my film, and exposing, in camera, to a zone 10 exposure (metered value, plus 5 stops):
Ok, I am hoping someone can help explain my results. Here are the details:
Tmax 100, exposed as e.i. 50 developed in a jobo drum, constantly spinning on a beseler motor roller developed in hc110, dilution H (half the dilution of B) for 12 minutes, 68 degrees
I have a densitometer which is acurately calibrated against a calibrated stouffer wedge.
For each "patch" on my stouffer wedge, I figured out what zone exposure it was allowing my film to be exposed to. For instance, "patch" number one has a density of .04, therefore, I am giving my film, behind the wedge, an equivalent to a zone exposure of 9.87.
math: 10 - (.04 / .3)
Ok, so, I plot out all my density results (y axis) against the derived zone exposures, (x axis), and the enclosed jpeg shows my plotted curve. The film base plus fog has already been removed from the data before plotting.
Aside from the exessive contrast (I should probably use a time closer to 10 minutes, for normal), why is my film speed low?
For my purposes, I am determining film speed by thinking that zone 1 exposure should be .1 . According to my chart, this speed is not reached until nearly zone 1.8, making TMAX 100, rated at e.i. 50 still needing to be bumped down to nearly e.i. 25!!! This doesn't seem right! I don't know of anyone deducting two full stops of speed from this film.
Here is the spreadsheet, if anyone who is going through something similar wants to use it, or look at it:
Last edited by JeffD; 02-20-2005 at 02:22 PM. Click to view previous post history.
Why not just shoot a white board for zone I to find your speed?
Money is not the problem. The problem is, I don't have any.
I had a similar problem with Efke PL 100 supposed to be iso 100 but I got only about ISO 27 when developing in a cibachrome drum rotating in a waterbath (constant agitation) with D76 in it. I suspected it was the constant agitation that did it, but that's just an uneducated guess. I swithched to T-max 100 (my favourite from 135 and 120) and used T-max RS in a tank (lift agitation every minute after 15 seconds initial constant agitation) and got about full speed. I should try again with the Efke film in the tank with same type of agitation some day when I get time and see if I get better results.
Have you ruled out other errors such as reciprocity failure, too fast shutter, too small aperture, inaccurate light meter?
It saves you sheets in case you guessed your speed wrong if you put a transparant wedge against your film
Originally Posted by djklmnop
I am shooting at 1 second w/ TMAX. My understanding is that reciprocity departure is not very significan't at one second for this film. I would think maybe around the order of 1/6 a stop or so, but that is a guess, if it is even that.
I have the shutter speed tested, so it is dead on.
I don't know for sure about my Pentax spotmeter. I guess that is the only other explanation.
I think the constant agitation in a jobo drub shouldn't decrease the speed- if anything, I would have thought it would maybe speed it up slightly. The hc110 unofficial resource page hints that you might have a slight speed reduction with hc110, but I don't think this significan't.
Hmmm. Not a big deal, but it is always nice when your tests bring about results close to what you think they should be!
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Jeff, I am not up to speed with all the HC110 dilutions, but I think you might be using it too dilute and are exhausting the developer too soon by using rotary developemnt.
I did calibration tests with HC110 diluted 1 part syrup to 19 parts of water and I got full speed both with TMY and Ultrafine.
That sounds possible, but I am using only 1 4x5 negative in the drum (which holds ten) and a full liter of solution.
Essentially, I am using the same amount of syrup I would use for 10 4x5 negatives (16ml), and mixing it with a liter of water (dilution h), instead of 500ml (dilution b), so there should not be a problem with developer exhaustion, I wouldn't think.
The reason I'm using dilution H is so that I can increase my times. The 6 minutes or so for normal development with dilution B makes for tricky going if you want to pull the film out earlier, for example, n-1 or n-2....