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02-23-2010, 07:25 AM   #1
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Total flash newbie needs help...

So in low light conditions when I activate the flash, the exposure metering in the camera does not seem to compensate for the fact that the flash will be going off.

In other words, if the camera says I need f 4, 1/2 sec, ISO 800 with the flash off, it still says that after I pop the flash up.

Clearly some adjustment needs to be made. How do I know what settings to use with the flash on? Trial and error? Or am I doing something wrong?

I'm a flash retard... maybe i need some kind of primer.

Thanks,

Ken

Using a K7 with kit lens

02-23-2010, 10:44 AM   #2
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QuoteOriginally posted by Javaslinger Quote
So in low light conditions when I activate the flash, the exposure metering in the camera does not seem to compensate for the fact that the flash will be going off.

In other words, if the camera says I need f 4, 1/2 sec, ISO 800 with the flash off, it still says that after I pop the flash up.

Clearly some adjustment needs to be made. How do I know what settings to use with the flash on? Trial and error? Or am I doing something wrong?

I'm a flash retard... maybe i need some kind of primer.

Thanks,

Ken

Using a K7 with kit lens
The camera should adjust the exposure at picture taking time and won't meter For the flash before then. It has no way of knowing how much light it will need before firing the shutter and analyzing everything. That's why we pay the extra money to get P-TTL on an external flash.

If you want full control over the exposure, even with the flash, go to M mode. In the auto modes, it should be automatic.

02-23-2010, 12:34 PM   #3
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Take a picture and check the EXIF data. I'll bet that the exposure has changed. As JeffJS said, the camera can't meter for the flash without the pre-flash to bounce back off the subject.
02-24-2010, 10:25 AM   #4
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Basically, with flash, the FLASH exposure is solely determined by flash power (actually duration, how long the bulb is actually firing for), aperture and ISO. Ambient exposure is determined by ISO, shutter speed, and aperture (just like without any flash), so the trick is balancing the two. If I'm indoors in a smallish room (such as in someone's house), I usually just forget about ambient since the flash is powerful enough to light up the entire room (hence the 1/180s below, if the flash didn't fire, I'd have a more or less black picture) Now although you're shooting MANUAL Mode, that's only for the ambient exposure (the exposure needle in the viewfinder will blink warning you about underexposure, but ignore that). The camera's P-TTL metering will determine the needed flash output for a proper exposure.

Here's something I wrote on another forum -
"Easy" recipe for great P-TTL flash shots -
1)Point flash at ceiling/wall (to the side or behind you, experimentation is the key!)
2)Put camera in MANUAL mode on the mode dial
3)Set FEC to +1 on the flash head

4)Shoot RAW (this allows you to recover some highlights that might get blown as a result of #3 above)

5)Set ISO to 200 (to start)
6)Set shutter speed to 1/180s
7)Set f-stop to whatever DOF you want


Now if the flash runs out of "power" because of high ceilings, you can raise the ISO or open up the f-stop to compensate. Or you can slow down the shutter to bring more ambient light into the exposure (in addition to adjusting ISO/f-stop) If the ceiling is REALLY high (like in a church), you may need a reflector to throw some of the light forward (I use the Joe Demb Flip-it).

Quick and dirty outdoor fill flash tutorial -
Basically, if your subject is in shade and the background is bright (ie under a tree) or majorly backlit, fill flash is your friend. Think of those times when you got a properly exposed background, but the subject was almost pitch black.

Put camera into Av mode, metering will set the shutter speed to expose the overall shot (which in the situations that call for fill-flash will generally be the background) based on your selected aperture/ISO.
Make sure flash is set to HSS (in case your shutter speed go faster than 1/180s) and P-TTL. Fire away! The shutter speed/f-stop/ISO will expose the background, and the flash should output enough power to light up the foreground.

Now to control the background exposure, you use exposure compensation on the camera body (which would adjust the shutter speed), to adjust how much fill for the flash exposure, you use Flash exposure compensation. The trick is balancing the two (as it is with indoor work), and that comes with experience/experimentation.

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