EV?

[mikethomas]

Hey guys,

I'm just looking through my EXIF data for my photos on my Pentax and I've noticed a value called 'EV'. Sometimes it's 0.0 EV other times It is displayed as +2.0 EV or +1.0 EV for instance. Is it an exposure value? (guessing). Because my more exposed images have a higher value and my darker photos have a lesser value. Forgive me if this sounds stupid but you've probably guessed I'm still figuring everything out..

First..is it a good idea to manually control this value? If so how?

Secondly, If I'm using say..Av or Tv mode..will The exposure be automatically set? therefore i shouldn't have to really worry about the value of it in the EXIF data?

Cheers

[RichardTaylor]

It is Exposure Value and the value is in F stops.

When manually controlling the exposure all you are doing is is increasing or decreasing the exposure in relation to what the camera is metering.

When using one of the "automated" modes the camera will determine the shutter speed or aperture, howvever you can "dial in" some exposure compensation (+- EV) if you feel it needs it.

For example I shoot a lot of motor sport, usually in shutter priority) and in bright sunlight I usually dial in -2/3EV to stop the drivers helmets (and any other white bits) blowing out.
(1)

Camera Canon EOS 40D
Exposure 0.003 sec (1/320)
Aperture f/10.0
Focal Length 400 mm
Exposure Program Shutter speed priority AE
ISO Speed 200
Exposure Bias -2/3 EV

[mikethomas]

Ok sounds simple enough!! thanks richard.

[sk66]

The question is, why is it changing if you are not setting it....

[candleman]

If it's changing by itself in Av, Tv or M ......I think you have enabled bracketing and don't know it.

Bracketing will automatically alter the EV with every shot at a pre-set amount.
usually 0.3 , 0.7 or 1 stop increments.

EV = the number of stops it will under or overexpose by.

Even in Av ot Tv, yes the exposure is automatic (within reason) ...however if you set a +0.7 EV it will force it to overexpose by that amount.. making it brighter.