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01/07/2005 02:12:42 PM · #1 |
Pretty much all digital cameras have a little display (when you're in manual mode) that shows whether you're underexposed or overexposed for what the camera sees through the lens. If I set up my D70 with my new SB-800 to take a shot of a flower and I point the speedlight at the ceiling and I have the camera in maual, is the camera taking into account the fact that I'm using a speedlight? Does it know I've pointed it to the ceiling instead of directly at the flower? Can I trust what it's telling me about the exposure? I haven't gotten all the way through my SB-800 manual yet (I know, don't kill me), and I'm having a hard time wrapping my mind around how it works- particularly since the over/under exposure display doesn't seem to change if I have the speedlight on the camera or not. Any clues?
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01/07/2005 02:42:53 PM · #2 |
The meter will show that it is "underexposed", because, well, it is -- the flash is just that, a flash of light for a split second, during which time the exposure will be "right" because the flash will add enough light to "get it there".
In order to determine how much flash power is needed, the cameras fires a metering pre-flash of a known power level right before the shutter opens. The camera meters this flash, and determines how much actual power is needed to properly expose the shot. The shutter opens and the real flash fires at the calculated power level.
Because the metering pre-flash also bounces off the ceiling (or whatever), in essence, yes, the camera/flash combo really is smart enough to "do the right thing".
This is one of the biggest differences between on-camera dedicated speedlights and studio strobes. With studio strobes, you need to use a light meter and adjust their power manually in order to obtain an accurate exposure.
Hope that helps!
Message edited by author 2005-01-07 14:45:33. |
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01/07/2005 02:50:19 PM · #3 |
Thanks for that Eddy.
So how does the photographer decide what shutter speed and aperture to shoot at, if the meter is metering for the available light? If I set it to be a full 3 stops underexposed, will the speedlight make up the difference? Wow, this is more confusing than I thought ;)
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01/07/2005 02:57:33 PM · #4 |
you would have to adjust the flashes exposure compensation to purposefully underexpose a shot.
i use an omni bounce on my 550ex, and set the flash exposure compensation to +2 so it doesn't underexpose the shot.
in manaul shooting mode - i set the aperture, and shutter how i want for DOF or stop motion, and let the flash do the rest.
at least i think i am correct in doing this ;}
the flash will adjust power based on your camera settings.
and available light present
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01/07/2005 03:07:13 PM · #5 |
Okay- so I should just set the aperture and shutter for what I'm trying to acheive (like for example, a fast shutter speed so I can hand hold), ignore the meter, and let the flash handle lighting the scene well enough for me. That makes it easy then. I can see this will require lots of testing. Thanks for the help.
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01/07/2005 03:14:41 PM · #6 |
Originally posted by EddyG:
This is one of the biggest differences between on-camera dedicated speedlights and studio strobes. With studio strobes, you need to use a light meter and adjust their power manually in order to obtain an accurate exposure. |
You mean you don't just spray&pray? Doh! I knew I was missing something. :)
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01/07/2005 03:26:35 PM · #7 |
yeah - but like the camera itself - combined with the flash it would be good to bracket until you get the hang of how the two work together.
i bet the flash has a bracketing option built in ;}
Originally posted by ahaze:
Okay- so I should just set the aperture and shutter for what I'm trying to acheive (like for example, a fast shutter speed so I can hand hold), ignore the meter, and let the flash handle lighting the scene well enough for me. That makes it easy then. I can see this will require lots of testing. Thanks for the help. |
Message edited by author 2005-01-07 15:27:07.
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01/07/2005 03:33:43 PM · #8 |
Originally posted by ahaze:
So how does the photographer decide what shutter speed and aperture to shoot at, if the meter is metering for the available light? |
It depends. If you are going for 100% illumination by the flash, then the shutter speed, in Manual mode, is largely irrelevant. Whether it is 1/15th of a second or 1/200th of a second, as long as you are below the X-sync (cross-sync) speed of your camera, the duration of the flash (which you have no control over and is usually measured in thousandths of a second) is what determines the "speed" and stops the action.
In terms of setting the aperture in Manual mode, that is mainly based on your desired depth of field. If you want everything in focus, and have the flash power to do it, you can shoot at Æ’/16 and the flash will try its hardest to put out enough power to properly expose the scene. (This can be tricky if there are things close to the camera though, since light output falls off with the square of the distance -- things close to the flash will get lots of lot and things far away won't get much at all.)
If you want to mix flash with ambient (using the flash only as fill and not the primary source of illumination), that is when you need to start dialing in negative FEC (Flash Exposure Compensation) and "dragging the shutter" to mix in the ambient lighting -- at least in Manual mode. On Canon cameras, using the Tv or Av modes (shutter and aperture priority, respectively), the camera meters for ambient light by default and only adds enough flash output for fill...
Flash photography can definitely be confusing, but can be quite rewarding when you start understanding it.
Originally posted by ahaze:
Okay- so I should just set the aperture and shutter for what I'm trying to acheive (like for example, a fast shutter speed so I can hand hold), ignore the meter, and let the flash handle lighting the scene well enough for me. |
Remember that your camera has a maximum X-sync shutter speed. You can't use the flash at faster shutter speeds, because the second curtain of the focal-plane shutter will start traveling before the first curtain gets to the other side. This results in "black bars" in your photo. But like I said above, typically it is the duration of the flash itself that stops the action, not necessarily the shutter speed, when you are using the flash for the vast majority of the exposure.
But the "ignore the meter" part is mostly correct -- unless you are mixing ambient into your exposure (then you need to be aware of the shutter speed). Otherwise, the camera/speedlight will work together to try and provide the correct exposure.
Message edited by author 2005-01-07 15:45:09. |
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01/07/2005 03:42:00 PM · #9 |
Thank you EddyG. I think I'm gonna have to read that about 10 times and take about 200 photos before it all sinks in!!
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