From: shannon stoney (sstoney@pdq.net)
Date: 04/13/02-09:47:59 AM Z
This sounds very useful! Yes, we do have excel on this computer.
Thanks in advance for emailing this to me!
--shannon
>Shannon,
> I checked this chart out that Gord mentions, below, and mine is
>infinitely more usable and understandable (how's that for being humble! But
>seriously...). However, it is an attachment and I would have to mail it to
>you offlist. It is an excel spreadsheet or a works spreadsheet so you'd
>have to have one or the other on your computer, but with one plug in of your
>pinhole fstop number all the times change for that particular pinhole. I
>also have every film speed on the left side of the chart so you basically
>choose your film speed line and run with it. I made the whole chart based
>on the following formula:
>
>(time @ f16)(pinhole f-stop squared)
>______________________(this is a "divided by" line)
>16 squared
>
>This is based on the inverse square law of light. I had to enter each cell
>with the calcs (which you, of course, don't see or have to worry about) and
>it was a b--ch so please acknowledge my authorship if you pass it along!
>(Christina Z. Anderson)
> How you use the chart, after you plug in the number, is that you take
>your hand held light meter, plug in your ISO and a shutter speed that
>matches that ISO (eg: 100 ISO of film and a shutter speed of 1/100 or
>actually 1/125) and get an fstop read. Then you follow that fstop column
>down to where the fstop column and the film ISO row intersect, and there's
>your time. Then you consult reciprocity failure on the left of the chart.
>This is based on the sunny 16 rule. If the weather is not giving you a
>sunny 16 but an fstop of even, let's say, f1 that you should be using, then
>you just consult the f1 column and run down it until you intersect with your
>ISO and there you have it. I have about 20 different pinhole fstops and
>that many charts, with the change of one cell on the sheet.
> However, if you are using Neopan Acros, there is no reciprocity failure
>until 128 seconds, and i mean NO. Then at 128 seconds you add 1/2 stop up
>until, I think it is 1000 seconds. So you do have to really watch your
>film's reciprocity failure. Maco IR film, for instance, is dismal in this
>department.
> I did a test; I took 12 different pinhole sizes on and off the front of
>my 35mm camera body cap. I tested each pinhole with my chart, using my
>calcs exactly, and exposed accordingly with Neopan Acros. Every single
>exposure I printed an 8x10 of at the exact same printing time. It proved to
>me that Acros was correct in saying there was no reciprocity failure. In
>fact, even when I added the 1/2 stop, it overexposed it just a tad.
> What is nice about this chart is that you can bring it with you in the
>field and when changing film from 3200 down to 1 ISO you've got all the
>times. The only thing is that the times are all in seconds, so when you get
>an f1 read on ISO 1 film you'll have some astronomical second count in the
>10,000's so you'll just have to divide by 60 to get your minute count. I
>don't suppose you'll often be shooting this speed of film in the dark, tho
>:)
>Chris
>
>> Hi:
>>
>> I use Larry Fratkin's pinhole calculator at
>>
>> http://www.MrPinhole.com/Exposure.html
>>
>> This web page does the math for you. You enter the f-stop of your camera,
>> it then creates a table that lists "normal" camera exposure times and
>> their equivilant exposures using your f-stop.
>>
>> To use the table you take a meter reading and find this on the table. In
>> the far left column on the same row as your meter reading you will find
>> the exposure for your f-stop.
>>
>> Hard to explain, but it works. I calculate the f-stop for each camera. I
>> feed this into the form print out the results and tape it to each camera.
>>
>> With this I can convert standard light meter readings on the spot without
>> doing any math :)
>>
>> Gord
>>
>> ---------------------------------------------------------
>> Gordon J. Holtslander Dept. of Biology
> > holtsg@duke.usask.ca 112 Science Place
>> http://duke.usask.ca/~holtsg University of Saskatchewan
>> Tel (306) 966-4433 Saskatoon, Saskatchewan
>> Fax (306) 966-4461 Canada S7N 5E2
>> ---------------------------------------------------------
>>
--
This archive was generated by hypermail 2b30 : 05/01/02-11:43:30 AM Z CST