New to Flash HVL-F43AM

Started Feb 13, 2013 | Discussions thread
windowsmaclinux Regular Member • Posts: 249
Re: New to Flash HVL-F43AM

Well unless your subject stands at the same distance always from the flash then having TTL makes your life easier.

A mode is just another automatic exposure mode because the camera picks the shutter speed and ISO for you. Full manual has a number of advantages. In general when the lighting doesn't change your exposure should not change. If you use A mode, depending on what's in the scene the camera will change the exposure (through shutter speed/ISO in A mode) to make the scene middle grey, which in this case is wrong because the exposure should be the same regardless of what you point the camera at (assuming the lighting is consistent in the scene). You should read up incident vs reflective metering to understand the advantage of M vs A/P/S.

A specific example: shooting outdoor on an NEX-6 with a 35/1.8 (which is identical to your 7 for the purpose of this example). The APS-C sensor gives me 50mm equivalent field of view. With this angle of view I know from the manual that the 42AM will have a guide number of 30m in normal mode. In HSS mode the guide number is 11m in HSS at 1/250. By the way GN = flash range x aperture for correct subject exposure. I'm also assuming that you want a shallow DOF for subject separation.

At first don't worry about the subject. Rather, try to have a correct exposure for the ambient light because you can't control it. If you have an incident light meter it'll tell you the correct exposure. If you don't you can use the camera's spot meter and meter off something that you know the correct exposure for e.g. fairly lust green grass or the blue sky 1/3 of the way up should be 0 on the camera's meter. Understanding incident vs reflective metering is important here. Also read up on the zone system. It never hurts to take a few test shots and chimp.

After having a good exposure for the background then you look at what aperture, shutter speed and ISO you have. It's probably bright enough outside so you're probably now at base ISO. Then look at your aperture and shutter speed. For the aperture that you want, will the correct background exposure cause the shutter speed to go above the sync speed?

If not you should be in good shape because the GN is 30m so for example if your aperture is f2.8 the flash range is roughly 10m, plenty for illuminating a human subject. Your flash won't be at full power so it should recycle faster.

If your shutter is above sync speed, say 1/250, you should worry a bit because the GN is now only 11m. If your aperture is f2.8 you have only 4m of flash range which might be enough. If you open the aperture up to f1.8 in the hope of gaining more flash range then the shutter is 1/500 and the manual says GN =  7.7m which still gives you 4m of flash range. You're not winning.

I hope you have realized that for a given outdoor lighting condition you're actually constrained by the output power of your flash and the ambient light is your enemy. A neutral density might help you in this regard and actually can be more efficient than using HSS but then a good ND filter costs a lot and 2-3 good ND filters/1 good variable ND filter might add up to a good flash.

I hope you also realize that the sync speed governs the efficiency of your flash because suppose your sync speed is 1/250 then you wouldn't have to go to HSS and lose flash power. That's why shooting at the sync speed will maximize the efficiency of your flash.

Maybe other posters with more experience will give you more specific guidance.

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