IR LEDs and Digital photography

I don't know much about cameras. I am at the stage where everything is pretty much trial and error. I do pretty well when i'm taking scenic pictures and night pictures, i know my way around my camera's manual settings, exposure, shutter, apeture...and what not.

But when it comes to pratical picture taking, like during parties, i find that my camera doesn't focus as fast as i want it to, especially in low light situations. I mean, when i'm taking scenic pictures at night, i can take dozens of pictures before i find the perfect setting. But in a party, especially when i'm outside, there is usually no usuable light around to assist my camera's auto-focusing capabilities. It usually takes me 2-3 tries before my flash-photos are decent; and by that time, my photo subjects are getting impatient.

So here is where the LED question comes in. I don't want to use my Surefire to light up there faces just so that my camera can focus properly. As a matter of fact, i don't even want to use my ARC LS or any other "visible" light...it's not very polite to do this to drunk college friends. Will IR LEDs work? Will it help assist in night time focusing for cameras...or does focusing need visible light? I've seen higher end digital cameras use a visible red LED or laser to assist in low-light situations. I wouldn't mind using a red LED...i would just look like a Borg or something...which is okay by me...i've always been the geeky one at parties. (You know, anti-social and everything. /ubbthreads/images/graemlins/grin.gif )

HMM, Good question!

I know that the Sony 707 and 717 cameras have built in IR illuminators.

Some cameras image sensors are more sensitive to IR than others but I don't have a clue about the focusing sensors in general.

I have a 16 LED IR illuminator kit... When I get a chance (It won't be today or probably not even tomorrow) I'll hook it up and try it out with my cameras and see if I can notice any difference.

THANKS Silviron!

I am aware of the two camera you have mentioned. My cousin has the F707 and i'm JEALOUS...of course it costs twice as much as mine. It shoots out several red lazers at the photo target before taking a picture. With almost ZERO ambient light, the camera does a flawless job at focusing...100%. The IR Illuminator you speak of also interesting. The sony cameras have the NightShot capability, i think that it is actually NV optics that take over. But i'm not sure.

BTW, i have an Olympus C700. I really hope that IR will help. If it does, Peter Gransee will have a nice check in the mail. /ubbthreads/images/graemlins/tongue.gif /ubbthreads/images/graemlins/grin.gif

If I'm not wrong, it's best for your beam to have a certain grid or pattern for your camera to lock on (Sony F707/F717). In this case, those optics that projects a square pattern of the LED die seems desirable. 5 watt non whites have this grid pattern. I think it may help. Anyone wanna do an experiment to find out?

I am not certain if IR would help much...

Most digital sensors ARE sensitive to IR light, but this is a BAD thing in color. For color sensors, they try to block as much IR as possible. If a camera has a separate focusing sensor (like a digital SLR), then IR may help. If, on the other hand, the imaging sensor is also used for focusing, then IR may not help.

Also, keep in mind that IR focuses differently than regular light. Have you ever seen a prism? You have blue and one end and red at the other. IR is off past red. A lens is just a special prism. Lenses are designed so that red and blue focus about the same, but they do not take any special care to be certain that IR focuses OK.

If you look at some old manual-focus SLR lenses, you may see a white or red dot that is used for focusing when using IR film. Just focus as normal, and then turn the lens a little more so that the dot is over the focus point. This is evidence enough that IR focuses differently!

Harrkev,

Thanks for the reply. I believe that my digi-cam uses the same imaging sensor for focusing. I don't think it has a seperate focusing sensor.

For what it's worth, i tried using my ARC LS with a red filter and took a fairly decent macro shot with flash in a completely dark room. It didn't take 2-3 tries to focus correctly. But then again, this was still a pretty bright visible light...i still don't know if a true IR light would help in this situation.

There was this talk about taking photography in complete darkness. Just use a high cut off infra red filter (above 800nm) on both the camera and the flash. They won't see the flash and the camera is all set to take infra red pics. Stealth photography at it's best!