General:Darkroom:The best repository for all aspects of LF photography and links is QTuan Luong's LF Home Page . The stuff below is just where I keep notes for quick personal reference. Test before using any of this on imortant things. ASA Number Sequence3 ,4,5, 6 ,8,10, 12 ,16,20, 25 ,32,40, 50 ,64,80, 100 ,125,160, 200 ,250,320, Fstop SequenceWhole stops 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90, 128, 180, 250, 360, 500, 720, 1000 Half Stops 1, 1.2, 1.4, 1.7, 2, 2.4, 2.8, 3.4, 4, 4.8, 5.6, 6.7, 8, 9.5, 11, 13.5, 16, 19, 22, 27, 32, 38, 45, 54, 64 Third Stops 1, 1.1, 1.3, 1.4, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3.2, 3.6, 4, 4.5, 5, 5.6, 6.4, 7.1, 8, 9, 10, 11, 13, 14, 16, 18, 20, 22, 25, 29, 32, 36, 40, 45, 51, 57, 64 To extend any of the scales above just double the figure two full stops below the unknown stop. So, to get the next third stop above f/64 you would double the number two full stops below that, 36, to get 72. You may need to round to get a convenient figure.
Basic photographic equations
where
To find the approximate bellows draw u needed by a lens of focal length f on a camera with a maximum bellows draw of v :
Notice that if f = v , the minimum subject distance will be at infinity.
Black & White Filter Factors

Filter Factors for KODAK BlackandWhite Films  

Filter Number 
PlusX Pan and TriX Pan Films (Values
in parentheses are for TMax Professional Films) 

Daylight  Tungsten  
the exposure by this factor 
increase fstops 
the exposure by this factor 
increase fstops 

Polarizer 
2.5 (2.5)  1 2/3 (1 2/3)  2.5 (2.5)  1 1/3 (1 1/3) 
Data is form the Kodak data sheet for the film specified.
Pinhole diameter = 0.03679 * sqrt(focal length)
f/stop = focal length / pinholediameter
coverage diameter = 2 * F * tan(acos(1 / 2 ^{s/4} ))
where
F = focal length of your camera
s = fstops of difference you are willing to accept the edge of the
image to have with respect to the center of the image
Note: This formula becomes simply coverage diameter = 2 * F when s = 2 stops.
Kodak codes are in their publication F3:
http://www.kodak.com/global/en/professional/support/techPubs/f3/f3.jhtml
Ilford doesn't seem to publish a separate document with this info. Look here for those and Fuji's (Kodak's are also here): http://en.wikipedia.org/wiki/Notch_code
This was compiled from several sources and shoved together. I carry a copy in my camera bag for quick ref. I have not tested every combination, so you should take the times as starting points and refine to meet your own needs. This is especially true of the Type 55 values—I got those from eyeballing the little graph in the data sheet, so beware! I use the TriX values with most nonTgrain films.
Metered  TMX  TMY  TriX  Type 55 
2 s  2 s  2 s  3 s  3 s 
4 s  5 s  5 s  6 s  6 s 
5 s  7 s  8 s  8 s  8 s 
10 s  15 s  20 s  18 s  17 s 
15 s  25 s  30 s  30 s  30 s 
20 s  33 s  40 s  45 s  40 s 
30 s  55 s  1 m  75 s  1m 5s 
1 m  2 m  2 m 30 s  3 min  2m 25s 
2 m  5m  6 m 30 s  7 min  5m 30s 
4 m  11 m  15 m  16 min  12m 20s 
10 m  40 m  40 m  50 min  36m 30s 
20 m  1 h, 5 m  1 h 30 m  2 h, 20 min.  1h 20m 
30 m  1 h. 50 m  ?  4 h  2h 12m 
TMX = TMax 100, TMY = Tmax 400 (original), 55 = Polaroid Type 55, TXP = TriX
See http://www.seeinglight.com/reciprocity.shtml for more on reciprocity.
TF2 is my standard fixer. I found the amonia odor of Photographers Formulary's TF4 to be too irritating (read smelly) for use in open trays. I only use TF2 for paperI still use TF4 for films in my Jobo.
TF2 is an odorless (really!), nonhardening alkaline fixer. Pretty much the same formula as F6 (see below), except for the omission of acetic acid and alum hardener. Disolve each ingredient in the order given. For prints I use the split bath method: 5 minutes in bath #1, 5 min in bath #2. When bath #1 approaches exhaustion, I toss it and move bath #2 to the #1 position and use a fresh batch for bath #2 and procede with fixing more prints. Capacity is 20 8x10 prints per liter.
Advantages of alkaline fixers:
One disadvantage is that there are no compatible hardeners except using risky chemicals.
To Make 
1 liter 
8 liters 

Water @ 125°F/52°C  750 
6000 
ml 
Sodium thiosulfate (Hypo)  250 
2000 
grams 
Sodium sulfite  15 
120 
grams 
Sodium metaborate  10 
80 
grams 
Water to make  1 
8 
liters 
Anchell's Darkroom Cookbook, 2nd ed. pg 215.
This is the usual F6 oderless fixer formula with ¼ the amount of hardener (potassium alum), as John Sexton uses it.
To Make 
1 liter 
8 liters 

Water @ 125°F/52°C  600 
4800 
ml 
Sodium thiosulfate (Hypo)  240 
1920 
grams 
Sodium sulfite  15 
120 
grams 
Acetic acid (28% solution)  48 
384 
ml 
Sodium metaborate  15 
120 
grams 
Potassium alum  4 
30 
grams 
Water to make  1 
8 
liters 
Mix ingredients in the order listed above. Make sure Sodium Sulfite is completely disolved before adding the Acetic Acid! Otherwise a precipitate will form and render your solution completely useless. Disolve the potasium alum in a small quantity of hot water before adding to the solution as the last ingredient to prevent sulfurization (per Anchell in Darkroom Cookbook).
Glacial acetic acid may be diluted to a 28% solution by mixing 3 parts of Glacial acetic acid with 8 parts of water. Always pour acid into water, never the reverse.
Use as a second fixing bath after the F6 bath before toning prints.
To Make 
1 liter 
8 liters 

Water @ 125°F/52°C  1000 
8000 
ml 
Sodium thiosulfate (Hypo)  240 
1920 
grams 
Polaroid's manual for Type 55 says to dissolve 1 lb. of Sodium Sulfite in 2 liters of water. That's just to make it easy for most people to remember, but that's more like a 22% solution and is a waste of good Na_{2}SO_{3}. If you notice that 180 divided into 1000 is 18% of the total volume, it's pretty easy to remember this way. The following was taken from Ansel Adam's book on Polaroid films.
Water, 27°C32°C 
750ml 
Sodium Sulfite (anhydrous or desiccated) 
180g (6.3 oz.) 
Water to make 
1000ml 
ASA  f/2  f/2.8  f/4  f/5.6  f/8  f/11  f/16 

100  6s  15s  35s  1m30s  3m30s  9m  22m 
200  2.5s  6s  15s  35s  1m30s  3m30s  9m 
400  1s  2.5s  6s  15s  35s  1m30s  3m30s 
800  1/2s  1s  2.5s  6s  15s  35s  1m30s 
1600  1/4s  1/2s  1s  2.5s  6s  15s  35s 
Equivalent areas:
20 8x10 = 10 11x14 = 5 16x20 = 3 1/3 20x24
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Page last modified:
16Feb2012