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[jim2386]

Hey guys,

Just want to get your suggestions on how to fix some of my photos. When I'm shooting in open water, I have an A570IS in manual mode with a S&S YS-27 strobe.

When I'm in open water, I shoot with a F8.0 to get the greatest depth of field and 1/60th shutter speed to prevent motion blur. I'm also shooting with a W-20 wide angle lens.

When I was shooting in low light level cenotes, in order to shoot long distances (farther than 6') I had to lower the aperature to something along the lines of a F2.8 etc.

I helped run a Discover scuba last week in the pool which has pretty bright internal florecent light. I shot all pictures at F8.0 because of the depth of field. However, this makes the person show up bright but the background is completely black.

I don't seem to have this problem outdoors, things are lit up nicely in open water behind the person. Is there a way to get better indoor shots? I figure if I lower my aperature to F2.8, the background will light up, but that will overexpose my subject that is much closer to me. Hopefully this makes sense. Let me know if you have any tips!

Thanks
Jim

 

[gogums]

If I understand your issue correctly then it sounds like your subject is overexposed because of too much flash.
I don't know the capabilities of your strobe when matched with your camera but are you controlling the flash manually or using TTL?
If you control your flash manually are you dialing down the power output when you open up your aperture?

 

[jim2386]

If I understand your issue correctly then it sounds like your subject is overexposed because of too much flash.
I don't know the capabilities of your strobe when matched with your camera but are you controlling the flash manually or using TTL?
If you control your flash manually are you dialing down the power output when you open up your aperture?

It's manual.

And yes, turning down the flash power makes sense, however, if I turn down the flash power and open the aperature, isn't that basically canceling each other out? Turning down flash power reduces over exposure, so then I go open up the aperature to let more light in and it over exposes again from the larger amount of light being let in?

 

[gogums]

Hi Jim. No they really are not cancelling each other out.

The quick and dirty response is "camera settings expose for background, while flash exposes your subject". While I agree with this...it took me a long while to figure out how to apply this "fact" in real world shooting. By the way, I'm still figuring it out

I'll try and explain how I digest that information and apply it while shooting. For me, it helps when I think about making an image using flash as being one image with two exposures.

1st exposure lasts the entire length of time that the shutter is open...say 1/60th of a second.

2nd exposure is the amount of time the flash is emitting its burst of light. Usually it is in the "thousandths" of a second.

The camera sensor will try to record any and all photons that can squeeze through the aperture opening of the lens (say f/8), regardless of where those photons came from (ambient or flash) for the entire time the shutter is open.

So, for example, you take your photo at f/8, 1/60 SS and flash at 1/2 power. The background is black or very dark and subjects in foreground look good, but you want to see more of the background.

So you open up the aperture to f/2.8 but leave shutter speed at 1/60 and flash at 1/2 power.

With a wider hole (f/2.8) you now allow more of the ambient light that is hitting the entire scene to enter the lens and register on the sensor. By opening up to f/2.8 you've allowed more of the light that was there all along to come in over the same length of time...1/60. The ambient light is not restricted to the narrower f/8 opening.

Great. The camera will "see" more of the background objects, but it will also "see" more light hitting your foreground subject.

It is this "extra" ambient light hitting your foreground subject that, when added to your unchanged flash power of 1/2, causes the foreground subject to be overexposed. Note: it's not really "extra" light. It was there all along when you look at the scene with your naked eye. The only thing it seems you've changed is you are now telling the camera to let more of it in with the larger aperture opening.

Remedy: Reduce the power of your flash by 3 stops (1/2 to 1/16) since you allowed in 3 stops more of ambient light (f/8 to f/2,8).

Let me know if this makes any sense! I'm sure others can explain it with more clarity.
Aloha!

 

[olyvtx]

here's how i learned flash photography....

First there's the natural "ambient" light, be it in a cenote or pool. Usually flash photography is done at 1/60th of a second, so your exposure time is fixed. If you want the "ambient" light to be properly exposed, you have to find the appropriate f-stop for that light level. For the pool, that f-stop may be f8. Now, if you want to add flash to your subject you can manually set the flash level for proper exposure. This, of course, is assuming you have manual control of your camera settings and flash unit's power setting.

For your descriptions of events, I would guess that in the pool, although there was sufficient fluorescent lighting, f8 at 1/60th underexposed the "ambient" light. Hence, the dark background. The only solution is to open the f-stop. To freeze motion you don't want to shoot any less then 1/60th sec.