Make sure your tape lets negligible light through.
.Been looking at the spread sheet, the 21st or 31st step is shown as being the chemical fog density, but these are defined steps and clearly, at least from my tests, contain density both from exposure and chemical fog.
I thought you were using the tape to block the light. If so then why don't you agree it must let negligible light through?
Why don't you just use the film's leader or trailer or inter frame spaces to measure the B+F ?
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It depends entirely on the amount of exposure you give during your test as to whether step 31 on the tablet contributes to exposure or not. Ralph's spreadsheet actually relies on there being no exposure for at least the last step, otherwise it can't work out the base+fog density which is critical for its calculations.
I thought you were using the tape to block the light. If so then why don't you agree it must let negligible light through?
Why don't you just use the film's leader or trailer or inter frame spaces to measure the B+F ?
Exactlyexactly!!!
come on, why should it let neglible light through, sounds like you are agreeing that where I want to read just fog must also have density from light. :confused:
yes, i do!come on, why should it let neglible light through, sounds like you are agreeing that where I want to read just fog must also have density from light. :confused:
yes, i do!
Originally Posted by CPorter (there was a url link here which no longer exists)
come on, why should it let neglible light through, sounds like you are agreeing that where I want to read just fog must also have density from light. :confused:
NO !!! The black tape used by CPorter as a mask should NOT let any light through. When I used the word negligible I intended it to mean "a sufficiently small amount (of light) that will not contribute to any measurable increase in density". Letting light through the tape that contributes to a density increase is contrary to the intention of using the black tape in the first place !!
hello,
after i did the first three tests with the stouffer 120 6x6 I got following results -> see pictures
the steps 30/31 and 1/2 are missing because the stouffer wedge was displaced in the hasselblad filmholder :-(
- why I have this "jump" on step 16 to 16 (other side of the step-wedge).
- what do you think about those results in general?
- should I have to repeat the whole process or should i go on with minute 13,4 and 19,5 ?
best michael
- why I have this "jump" on step 16 to 16 (other side of the step-wedge).
thx,i used a step wedge-negative placing in the hasselblad filmholder, photographing a white card placing on zone X; did this with 5 films!
maybe the displacing of the negativ leads to an uneven illumination (i lost steps 30/31 and 1/2)
should i repeat shooting 5 films
thx,i used a step wedge-negative placing in the hasselblad filmholder, photographing a white card placing on zone X; did this with 5 films! maybe the displacing of the negativ leads to an uneven illumination (i lost steps 30/31 and 1/2)
should i repeat shooting 5 films
One problem with the in camera contracted step tablet test is that lenses are brighter in the center than the edges. A nice long lens with a good size image circle would be the best way of minimizing it.
Mark, how are you determining speed/EI photographing the backlit wedge?
You'll laugh at this: I guess based on where various films hit .1 over B+F!
That's their ISO speed-point, and I know where that should be on the log E axis. Of course, developers shift that point, and there's no guarantee that the films themselves hit it exactly. But this gets me close. All my work has been comparative, usually comparing with XTOL's curves, so I haven't needed accurate log E numbers.
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