The guide-number tag has no wiki summary.
7
votes
2answers
1k views
What is the quantative relation between flash guide number and ISO?
I found that formula on the Internet:
Guide Number = (Shooting Distance * Aperture) ÷ ISO Sensitivity
Is it correct? If it is could someone please explain why ISO is related to guide number in this ...
5
votes
4answers
530 views
Does adding additional strobes cumulatively add to the flash power?
I've been reading articles that talk about using multiple strobes next to each other, all pointing in the same direction: as a means to add more light over what one flash can do.
Does the addition of ...
4
votes
1answer
166 views
How can I calculate the effect of non-TTL flash on exposure?
I recently got an old Canon AE-1 film camera back in working order. I'd like to use my modern 430EXII Speedlight flash with it, however since there is no TTL metering, I have no idea how much the ...
2
votes
2answers
119 views
Old Flash from the 70's
I have an old Consul 400 flash. It was distributed by Braun North America. I would like to figure what is the GN number at ISO 100, f/4, 10 feet.
2
votes
1answer
320 views
What is the relationship between Guide Number and flash power level?
From this post, I understand that the flash guide number (GN) is given by the following formula:
Guide Number = Shooting Distance × f-number ÷ ISO factor
I'm assuming that the GN calculated via the ...
0
votes
1answer
58 views
Guide number and exposure [duplicate]
I am having a bit of a difficulty calculating this.
Guide#= 32 feet at ISO 100
X sync speed= 1/250
Min ISO= 100
Max ISO= 800
What exposure values to expose to capture subject that's far away?
What ...
