Exposure Question

[Mobey]

I have a dilemma... two exposure scenarios both in the same light conditions same subject. I know I must be missing something here.

1) in AV mode I selected f/4 and got a 1/10 shutter speed at ISO 400.
2) P mode automatically selected f/4 with a 1/60 shutter speed at ISO 400.

Both had a speedlite mounted and on in ettl mode

With everything else being equal why is the shutter speed so different?

Thanks
Kevin

[number six]

The key is you were using flash.

By default when you set your camera to Av mode it will attempt to expose for the ambient light, using the flash as fill only. In P mode it underexposes the ambient light so the flash is the main lighting.

That's why I use manual exposure when shooting flash. I usually use Av otherwise, but with ETTL flash you can select a number of different aperture and shutter speeds, allowing the ETTL to control the overall exposure.

So if I want the flash to be the sole lighting I select 1/250 second at f/8, for example, and the flash will overpower ambient light.

-js

[Mobey]

Thanks for reading .....I figured out for myself...The flash preset the shutter to 1/60 in P mode. Now I just have to learn more about the flash interaction in other modes.

Just new to this and I have a lot to learn but having a blast!

Kevin

[Mobey]

The key is you were using flash.

By default when you set your camera to Av mode it will attempt to expose for the ambient light, using the flash as fill only. In P mode it underexposes the ambient light so the flash is the main lighting.

That's why I use manual exposure when shooting flash. I usually use Av otherwise, but with ETTL flash you can select a number of different aperture and shutter speeds, allowing the ETTL to control the overall exposure.

So if I want the flash to be the sole lighting I select 1/250 second at f/8, for example, and the flash will overpower ambient light.

-js

Thanks...

Kevin

[birdfromboat]

that one still gets me. I almost always shoot Av, but sometimes I have the speedlight on just in case I want to shoot with fill or in case I end up in impossible ambient light. I just can't seem to remember to turn on the flash and switch to M all in one slick move, it's more like flash on, fire away, chimp the histogram, WTF, oh (slap forehead) switch to Manual, try to regain composure and look like I meant to do that. Repitition has not helped me learn, I seem to repeat the same actions expecting different results. Oh well........

[neilwood32]

that one still gets me. I almost always shoot Av, but sometimes I have the speedlight on just in case I want to shoot with fill or in case I end up in impossible ambient light. I just can't seem to remember to turn on the flash and switch to M all in one slick move, it's more like flash on, fire away, chimp the histogram, WTF, oh (slap forehead) switch to Manual, try to regain composure and look like I meant to do that. Repitition has not helped me learn, I seem to repeat the same actions expecting different results. Oh well........

Thats one of the reasons that any time the flash goes on the camera, it goes to M straight away no matter what else I have been shooting!