On 5/30/2011 11:21 AM, Darkroom User wrote:
Ilford give times for ID11 for stock, 1+1 and 1+3, but how do I
calculate a time if I wanted to try 1+2?






I use a formula:

Time2 = SQRT(Dilution2/Dilution1) * Time1,

Where Time 1 is the time associated with the first (known)
dilution;
Dilution 1 is the number of components in the first dilution;
Dilution 2 is the number of components in the second dilution;
Time 2 is the desired time for the second dilution.

E.g., Dilution 1 is 1:1, so it has 2 dilution components
The known time for Dilution 1 is 10 minutes.
You are seeking the time for a 1:2 dilution, which has 3
dilution components.

Time 2 = SQRT(3/2) * 10 = 10 * SQRT (3) / SQRT (2) =
= 10 * 1.732/1.414 = 12.2 minutes.


--
Francis A. Miniter

Mesure is Medicine þauh þou muche ȝeor[n]e.
Al nis not good to þe gost þat þe bodi lykeþ,
Ne lyflode to þe licam þat leof is to þe soule.

William Langland, The Vision of Piers Plowman
Passus I, lines 33 - 35