# f-stop printing calculations

Discussion in 'Darkroom Equipment' started by Todd Barlow, Feb 23, 2006.

1. ### Todd BarlowSubscriber

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What is the formula that is used to calculate the times shown in the various f-stop printing sheets?

For example
If the base time is 8 sec:
+1 stop = 16 sec how do you arrive at +1/2 stop = 11.3 sec?

Todd

2. ### Bruce OsgoodMembership CouncilCouncil

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------------------------------------------------------------

This should give you a good starting point.

3. ### Lee LMember

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Todd,

I made up my own tables in a spreadsheet. If you can handle openoffice or Excel spreadsheets, the attached .zip file has both formats (done in openoffice) that produce an f-stop printing table. You can look at the formulae used in the spreadsheet to get an idea of how it works.

I just taught two 6th graders the basics of B&W, and since they'd just learned the basics of geometric progressions with camera stops and shutter speeds, f-stop printing seemed very natural and logical to them. I now use an RH Designs timer rather than these charts.

Lee

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4. ### vet173Member

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Thanks Lee, that is great. Helps us what got problems with cypherin.

5. ### leeMember

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RH Designs Stopclock timer will do this for you and is much more accurate but the trade off is it is more expensive.

lee\c

6. ### Marc LeestMember

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Simple

it would be T x 2^+f
(^ means to the power)
it would be
8 x 2^ +1 = 16
8 x 2^+0.5 = 11.31

M.

7. ### Lee LMember

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For those without a spreadsheet program, an f-stop timing table for printing is at: www.largeformatphotography.info/articles/f-stopTimingAdv.pdf
This is a .pdf file of a page from Way Beyond Monochrome.

I didn't mention it in my earlier post, but openoffice is free and very capable, and available for Windows, linux, solaris, BSD, and Mac OS-X. See openoffice.org

Lee

8. ### PieterBMember

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Yes I saw the .odt in your zip-file

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Todd:

Posters:

Joe

10. ### Gerald KochMember

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Do a google, there are several places on the web where you can download the images to make a calculator. Or buy a new/used copy of the Kodak Darkroom Guide which has one.

11. ### Todd BarlowSubscriber

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Thanks all... you have come through once again.

Todd