Canon 30D "Safety Shift"

[Janice]

Custom function 16 on the 30d is safety shift - enable or disable.
It is described thus "This works in the AV or TV mode. If the subject's brightness changes suddenly and the current shutter speed or aperture becomes unusable, the shutter speed or aperture is shifted automatically to obtain a suitable exposure".

Can anyone tell me how this is different from the usual run of things ie, you are in AV mode and choose F8. Suddenly the light changes and the shutterspeed alters to counteract that and obtain a suitable exposure.
Or if you are in TV mode and choose 1/125, the light changes and the aperture shifts to obtain a suitable exposure.

Cant tell how or why you would use it???

 

[pswillies]

A quick googling gave this http://www.naturescapes.net/072004/ej0704.htm#16

It seems that it's only really relevant at the extremes. i.e. You're in AV mode and set at the maximum aperture (f/2.8 say), but the shutter-speed required for a correctly exposed shot is beyond the capabilities of the camera. Safety-shift will automagically adjust your choice of aperture to a value that will give you the correct exposure.

 

[CT]

Agreed. The manual explanation is absolute pants, but that's what it is - if you're in AV and the camera runs out of compensatory shutter speeds during a light change, it will change the aperture to compensate. Vice versa in TV mode.

 

[Janice]

Ah thanks guys. Understand now. Now why couldnt they say that in the manual.....or would that be far too easy!!!