Tom Westbrook

General:

ASA Number Sequence

F-stop Sequence

Photographic equations

Filter Factors

Pinhole Formulae

Sheet Film Notch Codes

Reciprocity Chart

Night exposures

Print equivalent capacities

Darkroom:

Fixers

Sodium Sulfite Clearing Solution for Polaroid Type 55

The best repository for all aspects of  LF photography and links is Q-Tuan 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 Sequence

3 ,4,5, 6 ,8,10, 12 ,16,20, 25 ,32,40, 50 ,64,80, 100 ,125,160, 200 ,250,320,
400 ,500,600, 800 ,1000,1200, 1600 ,2000,2400, 3200 , etc.

F-stop Sequence

Whole 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

1/f = 1/u + 1/v

where

f = focal length
u
= image distance (i.e. lens to ground glass)
v = subject distance (lens to subject)

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 :

u = v * f / ( v - f )

Notice that if f = v , the minimum subject distance will be at infinity.

 

Black & White Filter Factors

Filter Factors for KODAK Black-and-White Films
Filter
Number
Color
Plus-X Pan and Tri-X Pan Films (Values in
parentheses are for T-Max Professional Films)
Daylight Tungsten
Increase
the exposure
by this
factor
Or
increase 
 f-stops
Increase
the exposure
by this
factor
Or
increase 
 f-stops
3
Light Yellow
1.5
2/3
---
---
8
Yellow
2 (1.5)
1 (2/3)
1.5 (1.2)
2/3 (1/3)
9
Deep Yellow
2
1
1.5
2/3
11
Yellowish-Green
4 (3)
2 (1 2/3)
4 (3)
2 (1 2/3)
12
Deep Yellow
2 (2)
1 (1)
1.5 (1.2)
2/3 (1/3)
15
Deep Yellow
2.5 (2)
1 1/3 (1)
1.5 (1.5)
2/3 (2/3)
21
Orange
5
2 1/3
4
2
25
Red
8 (8)
3 (3)
5 (4)
2 1/3 (2)
29
Deep Red
16
4
8
3
47
Blue
6 (8)
2 2/3 (3)
12 (25)
3 2/3 (4 2/3)
47B
Deep Blue
8
3
16
4
58
Green
6 (6)
2 2/3 (2 2/3)
6 (6)
2 2/3 (2 2/3)
61
Deep Green
12
3 2/3
12
3 2/3

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 Formulae

Pinhole diameter = 0.03679 * sqrt(focal length)

f/stop = focal length / pinhole-diameter

coverage diameter = 2 * F * tan(acos(1 / 2 s/4 ))

where 
F = focal length of your camera 
s = f-stops 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.

 

Sheet Film Notch Codes

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

 

Reciprocity Chart

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 Tri-X values with most non-T-grain films.

Metered TMX TMY Tri-X 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 = T-Max 100, TMY = Tmax 400 (original), 55 = Polaroid Type 55, TXP = Tri-X

See http://www.seeinglight.com/reciprocity.shtml for more on reciprocity.

 

Fixers

 

TF-2 Alkaline Sodium Thiosulfate Fixer

TF-2 is my standard fixer. I found the amonia odor of Photographers Formulary's TF-4 to be too irritating (read smelly) for use in open trays. I only use TF-2 for paper--I still use TF-4 for films in my Jobo.

TF-2 is an odorless (really!), non-hardening alkaline fixer. Pretty much the same formula as F-6 (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:

  • Washes out of prints in a fraction of the time.
  • No worries about toner staining (due to acid content of prints).
  • No need for a hypo clearing agent.
  • No fixer bleaching if left in too long by mistake.
  • Easier to mix (only 3 ingredients other than water).

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.

F-6 Odorless Acid Hardening Fixer (Sexton version)

This is the usual F-6 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.

 

 

Plain Hypo

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

 

Sodium Sulfite Clearing Solution for Polaroid Type 55

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 Na2SO3. 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.

18% Sodium Sulfite Solution for Type 55
Water, 27°C-32°C
750ml
Sodium Sulfite (anhydrous or desiccated)
180g (6.3 oz.)
Water to make
1000ml

 

Night Exposure

Exposure in darkness under average sodium vapor lighting
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

 

Print capacities

Equivalent areas:

20 8x10 = 10 11x14 = 5 16x20 = 3 1/3 20x24

 

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Page last modified: 16-Feb-2012