# Using calculators for photographic ends

• 05-20-2009, 11:01 AM
Tom Kershaw
Using calculators for photographic ends
Rereading the thread I started on reciprocity of available sheet films, I started thinking about using a calculator for other purposes related to photography. For instance, after calculating reciprocity failure, one could then run a count-down timer to time the exposure. Another use might be to calculate f-stop timing intervals from a spreadsheet or matrix of pre-existing numbers. Say enter 6 seconds at the minimum time and 12 as the end time, with 1/4 stop intervals, produces a list; 1.9, 1.6, 1.4, 1.1, 6. etc.

Would those with more experience in using programmable calculators care to comment on these thoughts?

Tom.
• 05-20-2009, 11:07 AM
I regularly use an ordinary pocket calculator (HP-32s) to compute bellows factors. I guess I could write a short program to automate it somewhat...just never bothered.
• 05-20-2009, 11:08 AM
Q.G.
I did a lot of high magnification work, and had a calculator always at the ready.
Made a small computer program that did all the different calculations i need in one go.

A version of that program, tailored to Zeiss/Hasselblad lenses, is online.

Still want to port it to run on PDAs, but haven't gotten round to it.

Reciprocity failure is to 'unruly' to capture in a calculator.
• 05-20-2009, 11:59 AM
Konical
Good Morning,

I use a calculator to determine changes in print-exposure times when I change sizes. Much of the time, experience gives me what I need, but the calculator provides reassurance.

Konical
• 05-20-2009, 01:55 PM
Frank Szabo
Quote:

Originally Posted by Q.G.
I did a lot of high magnification work, and had a calculator always at the ready.
Made a small computer program that did all the different calculations i need in one go.

A version of that program, tailored to Zeiss/Hasselblad lenses, is online.

Still want to port it to run on PDAs, but haven't gotten round to it.

Reciprocity failure is to 'unruly' to capture in a calculator.

Can't be any worse than scratch-writing a Fortran program for Simpson's Rule and that's not difficult (assuming a suitable quantity of adult beverages) ...

Couldn't reciprocity failure be expressed as one would a limit? (think beginnings of the calculus - not the stuff on one's teeth).
• 05-20-2009, 02:12 PM
Tom Kershaw
Frank,

See: http://www.apug.org/forums/forum37/6...eet-films.html - relating to the calculation of reciprocity failure.

Tom.
• 05-20-2009, 02:16 PM
archphoto
Reciprocity is for each film diferent.
I gues you are better of with a little cardboard with those data for the films you use most.

Peter
• 05-20-2009, 02:20 PM
Tom Kershaw
Peter,

In the thread I linked to Patrick Gainer discusses a formula for working out the needed increase in exposure to account for reciprocity failure, using a correction factor derived for each film type.

Tom.
• 05-20-2009, 02:44 PM
Q.G.
Quote:

Originally Posted by Frank Szabo
Couldn't reciprocity failure be expressed as one would a limit? (think beginnings of the calculus - not the stuff on one's teeth).

The important bit in this reciprocity failure thing is expressed by the word failure.
If there was an easy rule, an unequivocal relation, a simple formula, Bunsen and Roscoe would have found it ages ago.

You can explore the behaviour of films, and compile tables.

But - and this is important - you cannot (!) calculate reciprocity failure.
• 05-21-2009, 02:27 PM
sage
Ive written a few small ones as needed for my cell phone, as its usually always there and with me, and less to carry around to not need the calculator.