Simple Step Wedge Testing

[noseoil]

noseoil submitted a new resource:

(there was a url link here which no longer exists) - Simple Step Wedge Testing

Sooner or later people in photography come to the realization that their film and paper combination may not be able to deal with a scene which is not "normal." What can be done? The simple answer is, of course, a film test. This realization is met with trepidation by some and groans by others. Get a step wedge and start testing, but how? This procedure requires a bit of time, thought and a few sheets of film, but you don't need a densitometer to do a useful test.

Basics: Film speed is a...

(there was a url link here which no longer exists)

 

[Sean]

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.
Lee

By GeorgesGiralt - 02:59 PM, 02-14-2005 Rating: None
Hi !
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
Georges,
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.
Lee

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.

 

[Sean]

By Noah Huber - 05:07 AM, 08-13-2005 Rating: None
Tim - did you get your step wedge here in AZ? if so, where?
Also - couldnt I use a negative as a step wedge. . .. lemme splain - a negative of a stepwedge, is a stepwedge... right? assuming that there is no loss of density at either the high or low end of the scales.. cant the neg made from a step wedge be used as a stepwedge as well ? The steps, no matter the exposure (assuming all the steps are present) will still be 1/2 stops. . . . right?

By JeffD - 05:03 AM, 09-28-2005 Rating: None
Noah, the steps won't be exactly 1/2 steps a part do to film toe
and shoulder. the negative you get, though, when plotted on a curve, will show you what your toe and shoulder and general curve shape will look like, and also, hopefully, what you film speed is.