Question on lighting and shutter speed.why half my picture is missing when 2x shutter

[Dajuan]

You'd be able to exceed the sync speed if you were using speedlights instead of studio strobes. If you were using speedlights, then change the camera config to High Speed Sync, or the equivalent for your manufacturer. You can also exceed camera manufactures sync speed with PocketWizard Flex TT5s.

 

[Village Idiot]

You'd be able to exceed the sync speed if you were using speedlights instead of studio strobes. If you were using speedlights, then change the camera config to High Speed Sync, or the equivalent for your manufacturer. You can also exceed camera manufactures sync speed with PocketWizard Flex TT5s.

There's limits here as well. Not all hot shoe flashes have a HSS option. Even then, they become inefficient. The flexes (mini can do this as well, IIRC) have limitations with certain cameras and may only get you a third of a stop or two.

 

[RacePhoto]

Op... Change your shutter speed to 1 second, I bet you virtually get the same image. Why 1 second? Just so you learn that flash exposure isn't affected by shutterspeed unless you exceeded the sync speed.

BINGO! The shutter speed doesn't change the exposure with a flash! The flash duration is somewhere in the range of milliseconds, as you decrease the power, the flash duration also decreases, roughly in line with the power.

Canon Speedlites have a duration of about 1/750th of a second. So if someone uses a 60th or could sync. at 1/500th, the flash would be exposing the sensor the same amount of time. In a dark room a 1 second exposure would be the same as 1/500th.

If the OP wants more light, get a bigger flash, move the flash closer. Less flash? diffuser or move the flash back. You can also use power settings on some flashes and use the TTL features on some automatic cameras, in which case you can adjust the light that the camera will allow through the lens.

But no matter what, the shutter speed isn't the way to control flash except in the case of fill flash or daylight syncro matching.

 

[pgriz]

When using a flash that emits a single pulse, the sync speed is the fastest shutter speed you can use that will allow the flash pulse to fully illuminate the sensor. To overcome that, you need a camera/flash combination that emits a series of quick flashes which allows you to use a faster shutter speed than the sync speed. In the Canon system, that's known as "high-speed" flash setting. Because the light pulse is now actually a rapid series of smaller pulses, the range of the flash is reduced. This option is only available for ETTL, as the camera and the have to work together to determine the acceptable flash exposure duration.

 

[pgriz]

Setting aside ISO for the moment, here are some of the exposure/photographic relationships.
1) Ambient light exposure is controlled both by shutter speed and aperture.
2) Flash exposure is controlled by aperture, flash power setting and/or distance from subject. Note: NOT the shutter speed.
3) DOF is controlled by aperture and focal length (also the crop factor, but let's ignore that as well).

So, if you are shooting a scene with mainly flash (minimal ambient light contribution), then the aperture is set based on DOF considerations, the flash power is adjusted to give proper exposure (for the chosen aperture), and the shutter speed is set at the highest speed to ensure that the ambient light contribution is minimal.
- bright interior : ambient exposure would be 1 sec, at f/8 (iso 100). Assuming you want the DOF given by f/8, and your flash has a guide no. of 100, you'd set the flash at a distance of 12.5 ft. to get the proper flash exposure. If you set the shutter speed at 1/200 sec, that is 9 stops faster than what you would need to expose for ambient, and therefore the contribution from ambient will be essentially zero.
- full sun: Ambient exposure would be 1/200 sec at f/11. If you're trying to "kill the sun", then the flash should be at least 4 stops more powerful than the ambient, which means you'd need to have f/44. Using a flash with a guide number of 100, you'd need to set it 2 ft. from your subject to get enough light to make that exposure. Practically, most lenses don't go beyond f/22 or f/32, so you'd need a ND filter to reduce the light. A 2-stop ND filter will allow you to shoot at f/22 and get a four stop flash exposure (over ambient). As well, you'll probably want a more powerful flash since most people don't want to have a flash 2 feet from them.

If you are shooting a scene with some ambient light contribution, then do the above, but now lower the shutter speed to an appropriate value to allow more ambient light to enter.
- bright interior: using the above example, your exposure would need to be at about 1/4 sec. (2 stops below full exposure) to allow some ambient to show up. Everything else would stay the same.
- full sun: 2 stops below full exposure for ambient would be 1/200 sec at f/22. So now the flash needs to be set at a distance of 4.5 ft (guide no. divided by f/stop) to give you proper exposure with flash, and a two stop underexposure with ambient.

If you are shooting a scene with mainly ambient, but some fill, then you need to lower the flash power to several stops below the ambient exposure so that the flash does not compete with the ambient.
- bright interior: proper ambient exposure is 1 sec. at f/8, so you need a tripod. To give 2-stop underexposure for flash, you need to have flash adjusted for f/16, so a distance of 6.25 ft.
- full sun: if you're shooting full ambient at 1/200 sec at f/11, then 2-stop flash underexposure would be equivalent to f/22. The flash would need to be at a distance of 4.5 ft. to act as a 2-stop fill.

The other way to control flash power is by variable power settings on the flash. Instead of moving the flash back and forth to get the right amount of light, you can adjust the power setting on the flash to give you the right amount of light. 1/2 power is 1 stop, 1/4 power is 2 stop, 1/8 power is 3 stop, etc.

Of course, if you use umbrellas, light modifiers and bounce flash, the guide number calculations are useless. This is where a good flash meter becomes an essential tool, AND a good flash with the ability to change power/output levels becomes important, and you will not be using distance to control the light.

 

[Derrel]

I'm trying to do a white background by using 3 remote flashes. Two at the background, turning up the power to make my gray cloth white... while my third light firing at 45 degree in front of the subject... In this case a pillow.

While playing around with different shutter speed, one thing that struck interesting to me (which I cannot figure out) is why I cannot go beyond 1/200 sec on my shutter speed.

Here are two pictures to demonstrate my problem:

Although at 1/400 sec the picture looks like it would be properly exposed, but half my picture is missing. Why is that? at 1/320sec approximately a third of my picture is gone. And this seems to be related directly to my shutter speed. In the pictures above, the shutter speed was the only variable that changed, the ISO and Aperture stayed the same.

I got a feeling the answer to what's going on is a stupid one, but I can't figure it out!

Reminds me of the old joke about a guy who goes to his doctor and says, "Doctor when I do this with my arm, the pain just kills me!"

And the doctor says, "Well, then, don't do that with your arm!"

So....keep that shutter at 1/200 second or slower, and you'll be fine.