Technical Methods, Materials, Workshop Practices
I needed to really get my head around the parameters I was working with when it came to photograms. It turned out that in my next darkroom session, I didn’t manage to do nearly as much as I had hoped (see my aims at the end of my last photogram post), as there were more permutations of variables than I had realised, but I’m glad that instead of rushing through I decided to simply spend this time running a series of systematic tests to examine the relationships between these variables: the distance of the bulb from the backboard; the contrast; the aperture; the exposure time. I had in mind one of Justin (the print technician)’s maxims: “if you’re not testing, you’re guessing”. It took some time but I thought this was a very good principle to work by - it would save time in the long run by being sure from the beginning what the limits and options are instead of having to go back and try and recreate things which might have occurred by chance. It also allows some perspective to really think about which characteristics are important and which aren’t.
I set up a diamond shape using my pennies on a glass plate. The first two shots I took were intended to try and cover the whole range of contrast options. I wanted the highest contrast possible between my black and white, which I discovered doesn’t mean the highest contrast setting available, as extremes of contrast detract significantly from clarity. Each picture is split into 9 strips, going from a contrast setting of 170 down to 100 and then 50 on the left and then from 40 to 30 then 20 on the right. I kept the aperture the same throughout (fully open: F0) and switched between exposure times (30, 20 and 10 seconds), trying each of the three for every different contrast level. The height of the bulb for both of these I kept at the level where, when turned on, the short edges of the rectangle of light lined up with the short edges of the paper (this was around half-way up the arm).
These came out less neat that I was hoping. If I had adhered strictly to Justin’s testing/guessing maxim the previous time I was in the dark room I would have known or probably been able to guess the reason for this! Anyway I learnt from these two that adjusting the contrast all the way down from 170 to 20 didn’t make any difference what with the other settings as they were - the lines between the strips weren’t visible at all.
For the next pair I moved the bulb right up as far as it could go, remembering the effect this had last time. For the one on the left I did a similar thing with the contrast and exposure time - I tried three contrasts (50, 40 and 30), and three exposure times for each one (again, 30, 20 and 10 seconds). For the one on the right I decided to try adjusting the aperture too. Here I kept all exposure times at 30 seconds and went back to higher contrasts (130, 100 and 70) to see if the aperture change made a difference compared to my first sheet, trying 3 aperture levels for each contrast level - F0, F2 and F4 (F10 being the maximum, i.e. the smallest hole; the setting which lets the least light through). For these and then also for the rest from this session, I kept the bulb right at the top of the arm, a far away as possible from the coins as possible.
Now, it’s hard to tell with these scans, but the one on the left is actually really nice and crisp. The contrast settings are at a level where the exposure time differences are visible (the vertical strips of varying darkness), and the areas with the darkest backgrounds (the 30 second strips) are just about perfect for what I’m after I think, certainly in terms of straight-up clarity of edge between black and white. The one on the right seems to indicate that jacking the contrast right up will make for quite blurred edges regardless of changes of other parameters.
The first of next pair (number 5) I split into two halves: both kept a consistent exposure time of 30 seconds and tracked the aperture from one extreme to the other (six horizontal strips - F0, F2, F4, F6, F8 and F10 from bottom to top), and the left half had the contrast at 50 whilst the right was at 30. For the 6th shot, on the right, I tried directly compensating the aperture and exposure time: six vertical strips, going left to right with exposure times of 10, 20, 30, 40, 50 and 60 seconds and at the same time apertures of F0, F2, F4, F6, F8 and F10. In theory, the amount of light being exposed to the paper would remain (very) approximately constant, because as the aperture narrows to let less light through, the exposure time increases to let it through for longer.
So from picture 5 I learnt that I need to stay around the lowest (i.e. widest) aperture settings. In fact, with a 30 second exposure time, at contrast levels of both 30 and 50, the F0 section is the darkest, which is what I’m after. Picture 6 turned out to be a really useful test, because it clarified for me that even with a long exposure time, high/narrow aperture settings create blurred edges. The clearest part of this one was, again, the F0 section, and, surprisingly in fact, a 10 second exposure didn’t seem to darken the black much less than the 30 second exposure of picture 5.
For the last two shots I took in this session, I decided to try something slightly different - I had noticed previously that, even in some bands of unchanging settings, there was more blurring at the edges of the pictures than there was in the middle. I thought this might be something to do with the angle of the light in relation to the glass plane and the refraction through it (at the edges of the page the angle is smaller than 90 degrees, which is what it is in the middle, directly below the bulb). To test this I offset the whole sheet several inches to the left and also closer to where I was standing, so the diamond shape was right at the corner of the backboard. Then for the last shot (on the right) I bypassed the glass plate altogether and put the coins directly onto the photo paper. For both of these I kept the aperture at F0 and the exposure time at 10 seconds because that was the best combination from the last test. Also the contrast I left at 40.
They both came out really clear - the only difference was that the one on the left (which still had the glass plate) had very thin black outlines of circles which crept into the edges of the white ones I talked about this in the last post - I thought then that the reason for this was the refraction through the glass. I know think that much of the blurring of edges in previous shots from this session is probably caused by the same thing. These disappear in the one on the right where there was no glass plate. Out of all of these, the one which looks best is this last one - without the glass.
I might have saved myself some time by doing this in the first place! But I did learn a lot about the aperture/exposure time balance and the nature of contrast through all the tests with the glass plate, and I think it’s just this last problem (black circle outlines) which is solved by removing it and putting the coins straight on the paper. I think I’ll do this when making the drawing recreations. I will lose the functionality of being able to easily replace the photo paper without disturbing the coins, but the thin outlines do spoil the image for me (although it’s hard to see them on the computer screen) and having to replace the coins each time does, in a way, also bring the process closer to the process of drawing because of the time factor which is allowed to return (at least to an extent), which I think is interesting. It does make me think that, in many other situations (perhaps all situations in some way), there is a tension between time and the degree of control one has over the processes one puts into motion.
I’m looking forward to seeing how this tension makes itself known when trying out some drawing recreations next time.
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