Using calculators for photographic ends

Tom Kershaw · May 20, 2009

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.

BradS · May 20, 2009

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.

Q.G. · May 20, 2009

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.

Konical · May 20, 2009

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

Frank Szabo · May 20, 2009

Q.G. said:
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).

Tom Kershaw · May 20, 2009

Frank,

See: (there was a url link here which no longer exists) - relating to the calculation of reciprocity failure.

Tom.

archphoto · May 20, 2009

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

Tom Kershaw · May 20, 2009

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.

Q.G. · May 20, 2009

Frank Szabo said:
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.

sage · May 21, 2009

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.

Using calculators for photographic ends

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