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Is this right?

L

Lugztaz

[H]ard|Gawd
Joined
Jun 21, 2004
Messages
1,783
So I was getting ready to take pictures of some computer equipment I'm trying to sell. I got a flash from my dads old camera set and it's worked great. Now I pulled it out and it wasn't flashing. I fiddled with it for awhile and got it to work but the pictures are...not right.

Here are some quick pictures at different shutter speeds.

1/250

1/400


1/640


1/1000


1/1600


1/2000


1/3200



Now, these are all with the flash. Without the flash they are normal, is this normal? I'm under a florescent light and this flash is obviously old but I have no idea if this is wrong or normal.
 
Last edited:
ApEtc said:
A flash is effectively instantaneous. The amount of flash light picked up by the sensor is the exact same no matter your shutter speed. The shutter speed will only change the amount of ambient light. If you want to change the apparent effect of the flash you need to adjust aperture.

A lot of dSLRs nowadays have a sync speed of 1/200th or 1/250th, but a few have 1/500th. This means you have to use this shutter speed or slower for the flash to work properly. If you exceed this speed in normal flash mode, the shutter will actually already be closing by the time the flash fires and you will get what you are seeing above.

If the camera and flash support high speed sync, you can enable it and use the flash at even the fastest speeds. I believe the Rebel XT's sync speed is 1/200th, but it does also support high speed sync. Check your flash's manual to see if (and how) it supports high speed sync.
Click to expand...
This.
 
GLSauron said:
you're in M mode.
As you decrease exposure time, you get less light. Even with the flash.
Click to expand...

Why does it do it from the bottom up like that? Is that because the flash is pointing straight up or what?
 
So your saying the flash is not firing in acordance to the camera and it's settings? like maybe it fires to fast?

its possible, or you might have a setting wrong.
 
A flash is effectively instantaneous. The amount of flash light picked up by the sensor is the exact same no matter your shutter speed. The shutter speed will only change the amount of ambient light. If you want to change the apparent effect of the flash you need to adjust aperture.

A lot of dSLRs nowadays have a sync speed of 1/200th or 1/250th, but a few have 1/500th. This means you have to use this shutter speed or slower for the flash to work properly. If you exceed this speed in normal flash mode, the shutter will actually already be closing by the time the flash fires and you will get what you are seeing above.

If the camera and flash support high speed sync, you can enable it and use the flash at even the fastest speeds. I believe the Rebel XT's sync speed is 1/200th, but it does also support high speed sync. Check your flash's manual to see if (and how) it supports high speed sync.
 
Lugztaz said:
Why does it do it from the bottom up like that? Is that because the flash is pointing straight up or what?
Click to expand...

The shutter has two curtains that run from the bottom to the top of the frame, exposing the bottom of the photo first. When you're shooting at a shutter speed above the sync speed, the flash fires after the bottom curtain has already started to close.

here's a visualization: http://dptnt.com/2007/10/flash-sync-speed/

BTW, you can potentially damage your camera if you hook an older flash up that has a high trigger voltage, so be careful when you're using older gear with a newer camera.

http://www.botzilla.com/photo/strobeVolts.html
 
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