Illamasqua Plunge wrote in post #16987098
I'm not sure how you would expect to use a "chart" to replace a light meter. You only listed two of the factors that contribute to frame exposure. Besides the size of your aperture and iso, you also have to consider the total contribution of all other extraneous light, as well as the distance between the light source you wish to adjust and your subject. If the relative intensity of extraneous light is significant, then even your shutter speed can have a visually significant impact on your final frame exposure. Perhaps you should clarify how you intend to use such a "chart".
If all you want is a tabular list of f/stops to help you quickly determine how much aperture adjustment to make (in order to achieve a particular reduction/augmentation of light), here you go:
(2^0)=1
(2^0.5)=1.4
(2^1)=2
(2^1.5)=2.8
(2^2)=4
(2^2.5)=5.6
(2^3)=8
(2^3.5)=11.3
(2^4)=16
(2^4.5)=22.6
(2^5)=32
(2^5.5)=45.2
(2^6)=64
etc.
What I am interested in is what power Ill need to get an exposure I like based on a given iso/ fstop as well as a predetermined distance. A meter can give me a power percentage, it can tell me a recommended shutter speed, or, it can tell me a recommended fstop; it cannot tell me what to set my flash at (or, at least at the time I had one, I wasn't able to figure that out). In the meantime, a chart like the one Scott presented can get me that approximation; albeit, it presents 1/3 stops whereas I wanted one that could give me full stops ( using full stops are not as precise of course, but they are easier for me to work with). Shutter speed to control the ambient is to taste, so it doesn't hold as much weight in this particular process.
So, for example, if I want to illuminate my subject at f11, iso 200, at approx. 8ft with my bare 580exII, im probably setting my flash power @ 1/4 power, or thereabouts. If I want to illuminate my subject at f4, iso 100 with a shoot-thru umbrella, at 8ft, Im probably starting @ 1/16, then bumping up 2 stops because I lose about 2 stops shooting thru an umbrella, which leads me to an approx. power setting of 1/4 or thereabouts. Or, I can simply move the umbrella forward 3-4 ft closer to my subject to stay at 1/16 or thereabouts. Took me a while to kinda grasp all that.
Of course, that's with one or more of my speedlites in manual. A 360 isn't a speedlite, it is the equivalent of about 4-speedlites which makes it much more powerful. And even though I was able to work out the speedlite thing, Im having a more challenging time working out the 360 since all the numbers Im reading here vary from one person to another. Call me lazy, but I wanted a simple solution so I can get up and running as fast as possible with this light. Which is why I posted the question in the first place.
