Shutter lag on digicams

I hope this subject has not been discussed in depth but I could not find it in a search.

I can understand why the camera needs time to focus but why does it still have shutter lag after the button is fully depressed once focus has been obtained? Surely all the information required by the camera is acquired when the shutter opens and on my Oly this can be as fast as 1/4000. I am guessing that it has something to do with processing speed or memory because DSRL's don't have this problem but reason that that only becomes a factor after the shutter has opened. :?

why does it still have shutter lag after the button is fully depressed once focus has been obtained? Surely all the information required by the camera is acquired when the shutter opens and on my Oly this can be as fast as 1/4000

Your shutter doesn't "open". It is electronic. From the time you actually get focus lock, several things happen.

calculate white balance

calcultate exposure (pre-flash to get information)

close down aperture

activate the electronic shutter

initialize image processing components (clear the image that is on your LCD as you are framing)

These things are all done when you push the button, not as you are viewing the scene.

George hit it on the head. I think the main delay is that the camera has to switch from video capture mode (what you are seeing on the LCD) to "take photo mode." That takes a while and is the reason that you get much less shutter lag when the back LCD is turned off - kinda hard to frame the shot though...:-)

Cheers

James

Actually, many cameras calculate the exposure, and do the pre-flash, on the first half press of the shutter. My G2 does this.

The big thing, for SLRs, is getting the mirror out of the way. The 20D, which is very fast compared to the rest of the cheaper DSLRs, is 75 msecs.

For digicams, this is not the case, since they don't use a mirror viewfinder. And in fact, the latest sonys have final shutter lags of 9-15 milliseconds! And some of the more recent canons are not too bad - the G6 and Pro1 are around 70-80 milliseconds - about the same as the 20D.

The oly's really perform poorly in this regard. Being much slower even than SLRs - in the 125-250 msec range, (yes, that is near 1/4 second!!!).

Don