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| p.1 #7 · Flash Exposure Compensation v/s Manual mode ? |
Okay for all flash gurus here, I'm experimenting and learning more of OCF. So how do you figure out what is correct power for flash when you put flash in Manul mode. Is there any basic rule/guide for it or you simply do a test shot see on viewfinder how it looks and then set Falsh power accordingly ?
You didn't say what camera and flash. There are differences between Canon and Nikon flash systems.
Nikon's TTL flash meter is pretty good. But if I have time, I'll use a gray card to set my flash exposure.
For setting ambient light exposure, I'm able to spot meter my white-balance reference (which is about 30% gray or so) and then set 1.3 EV of Exposure Compensation (a value arrived at through a simple "calibration" process.) If I spot meter my WB card and set 1.3 EC, I get correct exposure. If I then take a picture of the card, the card registers as a spike right on the first line from the right side of the histogram. I can use this information to set exposure for flash.
I'll set up the key flash, put the WB card at the subject position, facing the flash, and in A mode I'll set the Flash Value Lock. The camera comes up with a flash exposure and locks it in. Now I take a picture of the WB card and check the location of the spike in the histogram. It usually only takes one EC correction to put the spike on that first line from the right side of the histogram. I take a second shot to confirm, and I'm ready to shoot.
The advantage of using FV Lock is that I can now change aperture at will, and the camera will adjust the flash power to provide the same exact exposure. I can put the camera in manual mode and increase the shutter speed into the High Speed Sync shutter range, and the flash exposure will remain locked and consistent. This provides quite a range of control over aperture and over the ambient light...from almost full ambient exposure to completely suppressed...without having to mess with flash exposure. Once FV Lock is locked there's nothing more to do other than tweak it with EC if I feel the need. It's a pretty quick setup as well. Just set the lights, hold the WB card at the subject position, take a picture of it, and review. Once you're used to the process you can set an exact exposure level in half a minute.
Note, however, that I'm talking about Nikon. With Nikon I can use Exposure Compensation to adjust the flash. You can't do that with Canon. Why does that matter? If you're using several wireless lights in two or three groups, using EC will adjust all of them at the same time. After EC has been adjusted for the Key light, you can then go into the Flash Commander and adjust individual groups, relative to the current exposure, with positive or negative FEC. This lets you set a key at one level, a fill at -1 FEC, another fill at -2 FEC, and adjust all three up or down with the camera's EC, without changing the relative relationship between the flash units.
This methodology requires more knowledge and understanding than the typical GN method or (more often) the trial & error method of all manual flash. It requires understanding your cameras functions. In that regard, it could be said that it's not "easier" than manual flash. But I don't care about "easy"...I care about function. Once set (a process which is quick to do) the control over the shooting parameters is unmatched in speed and ease. There's simply no way to adjust aperture or control ambient light as quickly and as consistently with all-manual flash as you can using FV Lock.