I'm having trouble with the autofocus in low light. It doesn't seem to work. Is this more the lens I'm using or the camera body? Any low light tips?

-- DEAN ANHORN (arrowhunter2@yahoo.com), March 24, 2002

Answers

What lens are you using? My Rebel does okay with lenses of about 2.8/3.5 and faster maximum apertures but does not do well with slow lenses.

-- Lee (Leemarthakiri@sport.rr.com), March 24, 2002.

Sadly, most inexpensive autofocus cameras are notoriously bad at focussing in low light conditions. And manual focussing is pretty difficult as well, partially because the viewfinders tend to be rather dim and because there are no manual-focus assist aids like split circles in them.

The best thing to do is probably to get an external flash unit. Most external flash units (including all of Canon's) have bright red lights which illuminate a patterned area, helping the autofocus system to lock on in low-light conditions. You can then turn off the flash before taking the photo if you want to take the photo with available light.

Canon also sell a device for triggering external flash units wirelessly - the ST-E2. It's got an AF assist light as well but no flash and is smaller than most flash units. So it's a good option, albeit an expensive one, for low-light autofocus assist without flash.

-- NK Guy (tela@tela.bc.ca), March 24, 2002.

When it is really dim--dim enough to need a tripod, it is best to use only the center cross sensor (I hope the AF sensors are selectable on a Rebel!?). Why is this necessary? The outer AF sensors--sensitive mainly to horizontal lines--have difficulty focusing in low light and/or low contrast situations. So, manually select the center sensor and turn off all other AF sensors. It is extremely important to lock focus on a contrasty detail, e.g., an eyebrow rather than a smooth forehead or the edge of a roof against the glowing skyline.

Low light AF is enhanced considerably by using a fast prime lens such as the EF 50 1.8 or EF 35 2.0, rather than a slow zoom. A stop or two of additional light makes a big difference in AF performance. The increased depth of field of a wide angle lens, e.g., EF 28 2.8, also helps improve low light AF. A bright image in the viewfinder is an further benefit of using a fast lens.

In candlelight murkiness or complete darkness, you must use the AF assist light of a Speedlite to autofocus. With a near-infrared AF assist light you may continue to use automatic focusing point selection. It's a shame Canon omitted the built-in near-infrared AF assist light. It made low-light AF elegant and convenient on the A2 and older Elans. If you don't want the flash to fire, you'll have to turn it off after AF while keeping the shutter pressed halfway to maintain AF lock (other EOS cams have a custom function to disable the flash but use the AF assist light). If you have good eyesight (or use the distance window) and a fast prime, you can still focus the old fashion way, manually!

-- Puppy Face (doggieface@aol.com), March 25, 2002.

if the ambient light level is really bad, focusing manually will not help not because there are no manual-focus assist aids like split circles in them but you won't be able to see the subject clearly through the viewfinder to focus it properly. when you switch the focusing mode to MF, the sensors within the camera remain active. so when focus is achieved, those focusing points get lighted below the viewfinder. so overall its just that instead of camera rotating the focusing ring, you are doing it for camera, may be to save power or to achieve focus in low light condition.

one should select the focusing points automatically. only then you will be able to see the effect properly. this is useful independent of whether your eye-sight is good or bad. if the camera is not malfunctioning, it will show the correct focusing points which achieves focus when you focus manually.

assuming that you have selected the focusing points automatically, and trying to focus manually, then there is an interesting point to be noted. you will find that when the focus is achieved (i.e. 1 or more focusing points lights in the viewfinder/LCD display), these points are not stable but keep on changing. i mean different points get lighted. this happens mainly when you hand-hold the camera. this gives a how un-stable your camera is in your hand. this give rise to camera shakes.

-- sajeev (chack74@yahoo.co.in), March 25, 2002.

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-- Osama bin Laden (obinladen@alqaida.org), March 27, 2002.

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-- Venkat (venkat_p_iyer@yahoo.com), March 27, 2002.

Actually it's getting quite juvenile.

-- Mullah Mullah (mullah@mohamed.org), March 27, 2002.