Camera Dojo - Latest Comments in Using your flash’s guide number

Re: Using your flash’s guide number

Pierre — Thu, 18 Sep 2008 09:53:36 -0000

Sorry, I understand... it's the metter's convertion ( :

Re: Using your flash’s guide number

Pierre — Thu, 18 Sep 2008 09:46:08 -0000

Hello,
Thank you for this tutorial.
But there is something that I do not understand.
With a Canon 580exII, I have to use 190 or 58 NG in the Calculation Spreadsheet?
I do not understand the 190 number if the number of guide 580exII is 58?

Thank you for your reply (I don't speak English very well)

Re: Using your flash’s guide number

Tyler G. Hicks-Wright — Tue, 02 Sep 2008 04:12:59 -0000

Kerry,

I'm gonna call you out again. ISO multipliers follow the inverse square law, just like apertures, so the table should read:

100 - 1.0
200 - 1.4
400 - 2.0
800 - 2.8
1600 - 4.0
3200 - 5.6
6400 - 8.0
12800 - 11.0 (Only for D3 owners...)
25600 - 16.0

Seems much easier to remember, since that same scale is written on my lens and programmed into my camera, and it's correct! Of course, it's not exact, ISO 200's multiplier should really be 1.41421356... but it's close enough.

Best,
Tyler