comments from the previous article system:
By mikeb_z5 - 12:35 AM, 01-28-2005 Rating: None
when you make the print is that a contact print or do you place the negative in the negative holder?(I'm thinking contact print).
By noseoil - 12:43 AM, 01-28-2005 Rating: None
Mike, it is indeed a contact print. The example I have shown is on grade 2 azo made by placing a sheet of paper, then the film on top and then cover the sandwich with a sheet of glass. I use a flood lamp and an old Kodak timer. This print took about 30 seconds, azo is pretty slow.
By noseoil - 02:20 PM, 01-30-2005 Rating: None
Mike, no reason you can't enlarge for a film test and print as you normally would. Just be certain to have a nice black edge for FB+ fog exposure..
See my post on "Exposure" about zone 1 and film testing for more questions about this stuff. tim
By JeffD - 03:21 AM, 02-09-2005 Rating: None
I was trying to do something like this the other night. I was testing Tmax 100 film, and, after metering my blank wall, and adding 5 stops of exposure, my exposure times were over a second, even with my lens wide open at 5.6. That concerned me, because I didn't want to be in an area of potential reciprocity failure. So, I moved my lamp closer to the wall. Unfortunately, when the light source is close, you create a small hot spot on the wall- in other words, the center of the film sandwich gets more exposure than the edges, by a pretty substantial amount. Probably by having my light source closer, I was introducing more flare into the exposure too.
Not too sure how best to progress past this point... comments?
By JeffD - 03:26 AM, 02-09-2005 Rating: None
By noseoil - 12:34 PM, 02-09-2005 Rating: None
Jeff, I'm sure. Tmax 100 must have a chart showing reciprocity somewhere in Kodak's web pages. If reciprocity does not become a factor, until say 3 seconds, you will be fine. My caution was aimed at most of the older types of films, not necessarily the "T" grains. If the Great Yellow Father says it won't be a problem, then go right ahead and test.
There is no reason you can't test for reciprocity with a step wedge, we just need to be careful to understand that the exposure is actually showing what we want in a test. That was my caution at the beginning in basics. tim
By Lee L - 01:18 AM, 02-12-2005 Rating: None
I use a daylight balanced compact flourescent bulb in a desk lamp and shoot through either a piece of white diffusion plexiglass or a Wallace ExpoDisc (over-the-lens diffuser substitute for a gray card) right up against the lens, at whatever distance from the lamp gives me the right exposure range. This gives even lighting at shorter exposure times.
By GeorgesGiralt - 02:59 PM, 02-14-2005 Rating: None
Would it make sense to use an electronic flash for exposure in order to stay away of reciprocity failure ?
By Lee L - 09:41 PM, 02-14-2005 Rating: None
Electronic flash exposures can be so short that they have "High intensity reciprocity failure" HIRF (as opposed to the low intensity reciprocity failure more often discussed). If you test with an electronic flash, either put it on manual with full output, or move it well away from the target on auto so that it uses a longer flash duration. Auto flashes control exposure by shortening the burst, which can get you into the region of HIRF at shorter than about 1/10,000 second.
By JeffD - 02:24 PM, 07-06-2005 Rating: None
I got around my hot spot problem, above, by obtaining a somewhat translucent piece of plexiglass material. I placed my light sources behind it, aiming at the back of the sheet, and put my camera lens fairly close to the front, to get a fairly even illumination across my film. I learned a lot doing these tests, and got some good hard data on my exposure and development times, which have helped me a lot. I'd encourage anyone thinking of doing this exercise to go for it.