I want to start doing my test strips using the f-stop method. So far I'm able to work out 1/2 stop increments, not exactly difficult even for my poor maths ability. However this has been a little coarse and I think it would work even better if I used 1/4 or finer steps.

Is there a formula, or rule of thumb for calculating these small increments, or some other resource, such as a chart or table available? I know there is a timer which supports this feature but that is outside of my budget constraints, at least at the moment.

Cheers

Martin

Here is a chart that may be helpful. It is in Adobe pdf format:

http://www.ktphotonics.co.uk/pdf/FstopTiming.pdf

Regards,
John

I have a trick for 1/3 stops if you happen to forget your math and your charts. Look at the light meter ISO settings; ISO 100 for 1 second, ISO 125 for 1.25 seconds etc. It is not high math but it is close enough for me.

Hi,

On this site there is a compuetr programme available (for free) that will do all the sums for you.

http://www.bonavolta.ch/hobby/

The formula is very simple :

n
Tb*2
with Tb : Base Time
n : Stop fraction ( -1, -1/12, ...,0, 1/12, +1)

Eric.

you must read "2 power n" in previous reply.

There's one guy in the NET that made a freeware program for a Palm that will do that.
I've designed for him an interface so the Palm can control an enlarger.

I do not know his site, but if someone is interested, pls PM me and I will send his email.

Jorge O

Here is another pdf chart that prints on a single piece of paper.

My f-stop chart (http://www.largeformatphotography.info/articles/f-stop-printing.pdf)

Kind Regards,

It can't get any simpler than just printing out the chart. I used this until I bought a F-stop timer. Nice job on your chart GreyWolf..

John