Simple Step Wedge Testing

Simple Step Wedge Testing

  1. noseoil

    noseoil Member

    Messages:
    2,898
    Joined:
    Oct 6, 2003
    Location:
    Tucson
    Shooter:
    Multi Format
    noseoil submitted a new resource:

    Simple Step Wedge Testing - Simple Step Wedge Testing

    Read more about this resource...
     
    Last edited by a moderator: Feb 6, 2016
  2. Sean

    Sean Admin Staff Member Admin

    Messages:
    9,297
    Joined:
    Aug 29, 2002
    Location:
    New Zealand
    Shooter:
    Multi Format
    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.
     
  3. Sean

    Sean Admin Staff Member Admin

    Messages:
    9,297
    Joined:
    Aug 29, 2002
    Location:
    New Zealand
    Shooter:
    Multi Format
    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.