Contrast Auto Focus vs Infra Red

[Sdashiki]

Ok, I am always shooting in low light situations for work.

Large conference rooms, lowered lights for a PowerPoint presentation.

And my Olympus dSLR uses contrast focusing, I think. Which means, if its dark it has to pulse the flash (much to the anger of my subjects who go blind) to get enough light and focus correctly.

Id focus manually, but the focus screen is matte, Id have to buy and install a split image...not really my idea of fun.

Ive used dSLRs that use infrared light to check distance and focus using that, much better in low light. But of course not useful in ALL situations, but its not even an option on my Olympus.

Is there a reason I find FEW dSLRs that actually use infrared focusing anymore? Cant cameras have both!?

 

[ChrisA]

The "IR" focusing is really just the same contrast method. What the IR system does is project a pattern of vertical bars on the subject. The normal contrast system sees these bars and focuses just as if the lights were turned on. Why is this not more common? It costs a few bucks for the IR lamp and at the low end people care about the few bucks.

The other method is to use the distance scale on the lens. If the subject is 8 feet away just set thelens to "8".

I'd prefer to manually focus with a split screen focus aid. If you are shooting during a point point briefing I doubt your subject is moving very fast so manual focus should be easy if only you had the split screen thing that use to be standard in all 35mm cameras.

 

[Abstract]

The Olympus strobes the flash because it uses contrast AF. It strobes the flash to provide very short, temporary moments of light so that the AF system can work. Same with Canon, Pentax, etc. I'm not sure if all Canon models do, but I know the 350D strobes the flash.

Nikon's use a little light on the front face of the camera, and never strobes the flash. I love it. Like Chris said, it just projects vertical bars onto the subject so that the AF can work.

 

[isleofjib]

could you put some sort of IR filter over the strobe that flashes and maybe that would help cut down the amount of light being pulsed while still allowing the camera to focus?

 

[Sdashiki]

Methinks I just gonna have to buy a replacement focus screen. THey sell split image ones, just seem like a pain to install.