Re: Determining film speed.
Quote:
Originally Posted by
Fredrick
Determining speed and development for 8x10 with 8x10 sheets will be immensely expensive, seeing I need a lot of sheets if I am to follow what "The Negative" preaches.
-Fredrick.
To minimize the number of sheets used for testing, a spare darkslide (or one that is cracked, etc.,) can be used to get a lot of exposure info on a single sheet of film by drilling several holes in it and sequentially taping over the holes with an opaque tape for various exposure times. A thin black electrical tape could be used over the holes.
To test a film in 1/3rd stops from what is initially assumed to be 2/3rds under to 2/3rds over, five holes are drilled a few inches apart in a column on the left side of the sacrificed darkslide. Then, four of the holes are taped starting from the bottom. Once a loaded holder is in the camera, the good darkslide is removed and the drilled darkslide is inserted in its place. A Zone I exposure is made at an assumed proper film speed. The drilled darkslide is removed and all but the second hole is covered. The drilled darkslide is reinserted and another Zone I exposure +1/3 stop is made. This is repeated down the column of holes to produce five different exposures for Zone I on the same sheet. A reducing back and 4x5 film holders could be used to do the testing by either cutting an 8x10 sheet into identical quadrants or making sure a 4x5 sheet came from the same emulsion run as the 8x10 box.
Note that several variations are also be possible by flipping the darkslide so the holes are on the righthand side of the darkslide. The range of Zone I bracketed exposures could be extended or, a different Zone exposure could be paired with the Zone I exposure previously made. Or, a different Zone exposure could be given each hole at a constant EI to get Zones 0-IX on a single sheet.
Another variation would involve drilling the darkslide to obtain a row of three holes, left, middle, and right, repeated down a column for five rows. Three different Zone exposures for each row could be made moving the tape between each exposure. If done for exposures of Zones I, V, and VIII per row, fifteen different exposures could be developed identically on the same sheet. This would allow the paper threshold to be tested along with the speed point and middle gray reproduction for five different EIs.
Once the EI is established and the film development evaluated for matching the paper threshold, other sheets could be exposed identically to the full Zone range, but developed differently. With four sheets, an idea of proper film speed (first sheet test) and N, N-, and N+ developments could be given a full set of Zone exposures, ten per sheet (not using the middle column for the last three sets). If done with a reducing back and 4x5 holder using the quadrants cut from a larger sheet of film, the latter tests could be done from a single sheet of 8x10 film.
Re: Determining film speed.
Quote:
Originally Posted by
Fredrick
I already have some negatives that I need to develop. Those are rated at ISO 100. If they are too thin where I want details in the shadows, I'll try with ISO 80 or 50 - depending on how thin they are. No reason to waste a lot of sheets.
-Fredrick.
I'm with Bill, this is a great plan.
However, I will add one additional, obvious possibility. You could also analyze your approach to the amount of shadow detail you are getting. If you metered on something you thought was possible/reasonable, its could be that even more is possible than you imagined. That's one of the reasons we do large format, after all, more detail, or definition.
If you meter darker in the shadows, its the same as rating the film lower...
Lenny
Re: Determining film speed.
If you don't want to spend a whole lot on determining your film speed, pick your film/developer combination, and shoot two negatives.
1. A very dark card in shade on zone 1 for 1/2 of the manufacturer's recommendation (so for t-max 400 shoot zone 1 at 200 asa.
2. A very light card in sun on zone viii at the same ASA
Develop them together for the same time. If your lucky the zone 1 will be .10 above fb+f and the zone viii will be about 1.25 above fb+f. More than likely your going to be pretty darn close on the zone 1 neg. if not you can interpolate. And more than likely you will be off a little bit on the zone viii (i.e underdeveloped). Again, interpolate.
If you find that you are undeveloped a little bit and you interpolate to lengthen your development, its probably a good idea to increase your ASA by a third of a stop or so, and vice versa, if you find you are too dense then decrease your development and lower your asa by a third of a stop.
It really shouldn' take more than 4 negs to get real close. Just make sure you do everything the exact same each time you do it.
And if you are using 8 x 10, just cut one 8 x 10 sheet of film into 4 pieces in complete darkness and use some tape to tape them to the holders. that way you only need to use 1 sheet for the test.
Make sure your camera is set on infinity focus for the test (but then you already knew that)
I