Digital Compact Camera Auto Focus query.

davetrousers

Morning all,

In the olden days I had a Minolta 35mm compact camera that had auto focus and it would use infra red to help it focus. Now I have a Casio Exilim EX-Z1200 that just uses available light to focus, that can mean that in dark situations it can struggle to focus quickly.

Now to me, it seems odd that many digital cameras have gone away from infra red to focus, but I am in no way an expert. So I would be grateful to hear people's thoughts on this. I am not currently thinking of getting a new digital camera but it would be good to know if any cameras use infra red, and to gt people's thoughts generally.

Thanks for your help.

Strider590

Most compact digital camera's have both passive and active auto focus, it sounds like your Casio is purely passive.
Looking briefly at some reviews, im consistently seeing comments like "no frills digital pocket camera".

If your looking for a new one, try checking out http://www.dpreview.com, their reviews are pretty good.

isofa

Many still do!

Active autofocus (on older cameras and many compacts) uses ultrasound or IR to send out a beam for the focus, they read the reflected beam similar to sonar.

Active systems are useless on surfaces which reflect such as glass, and in general aren't as accurate as passive systems.

Passive autofocus (DSLRs and high end compacts) uses contrast detect, and will either fire a light beam (white or IR) or fire the flash in low light to ascertain the contrast levels. I've always found contrast detect focus to be extremely fast and accurate in normal lighting conditions.

My pro Canon Speedlite flash use IR beams (or very low red light) to assist with focus.

bob_a_builder

I seem to recall an orange led on the front of the camera coming on in such situations, and my previous camera was a Casio too ( broken now but I though it did it too)