Focusing in extreme low light?

[dannequin]

I have a Rebel XT, just sold my 50mm 1.8 and Sigma 10-20... so lately I've been shooting pictures for a friend who DJ's, and the lighting in the club is very limited. The only time I get good lighting is when they flash the lights during parts of the music...

I'm using my Rebel XT with my 18-55... I've looked at custom functions with AF Assist and other things, but I don't find that helping the best. What are some other options that I should look at for taking photos in basically pitch dark? I don't like to use manual focus, but have had to in order to get some decent shots.

[ManuGD]

I think you need to buy a fast prime!

[iAMB]

Are you using flash?

[dannequin]

I use the pop up flash for now because it's not a big environment...

Would the 10-22 EF-S be a fast prime?

[Roy G. Biv]

I use the pop up flash for now because it's not a big environment...

Would the 10-22 EF-S be a fast prime?

"Prime" = Fixed focal length ie. 50mm
"Fast" = 1.8 - 1.2

Your 50mm 1.8 that you sold was a fast prime but sucks in low light for AF.

[mike_d]

I use the pop up flash for now because it's not a big environment...

Would the 10-22 EF-S be a fast prime?

No, that's a zoom. Prime lenses have only one focal length, like the 50mm f/1.8 you had which is actually a pretty quick prime.

[District_History_Fan]

Honestly, something other than an XT body would be a serious improvement to. It hasn't got the greatest Af.

[hollis_f]

I use the pop up flash for now because it's not a big environment...

Get a proper flash. It will perform better than the built-in one and it has an AF-Assist function to help in low-light.

[neilwood32]

Try searching for night club photography in the forum search and you will find lots of useful ideas.

[toxic]

Your options:

1. Get a newer camera
2. Use fast lenses (f/2.8 or wider). I'm assuming that camera has an extra-sensitive center point with f/2.8 or faster lenses
3. Get a hotshoe flash with AF assist (Canon 430ex or above)
4. Learn how to focus in poor lighting - contrast edges, focusing on another object in the same focal plane
5. Learn how to manual focus

[Rudeofus]

To all those recommending fast primes: I hope you all are aware that the camera's AF system does not take advantage of anything faster than F/2.8. An F/1.2 prime might give you all kinds of creative options but (assuming similar lens quality) no better AF behavior than an F/2.8 zoom.

[hollis_f]

To all those recommending fast primes: I hope you all are aware that the camera's AF system does not take advantage of anything faster than F/2.8. An F/1.2 prime might give you all kinds of creative options but (assuming similar lens quality) no better AF behavior than an F/2.8 zoom.

Apart from the fact that it lets more light into the camera. Which will improve AF.

But apart from that - no difference.

[toxic]

Apart from the fact that it lets more light into the camera. Which will improve AF.

But apart from that - no difference.

The AF system performs no faster with f/2.8 than it does with f/1.

My work deals with low-light shooting a lot, like wedding banquets in rooms that are as dark as a cave. Sharp (correctly auto focused) images are very important because my prints are mostly 8" x 10." My EF24-70mm, f/2.8L autofocuses a bit slowly in extremely low light. When focusing a subject about 25 feet @ 70mm, it doesn't hunt, but it takes a while for the focus point (a non-cross type) to focus. To improve autofocusing performance in low light, I have been considering getting either a f1.2/85mm or f1.8/85mm and/or a f1.4/35mm or f2/35mm. However, I am concerned that in extremely low light the EOS-1D Mark II will be slow to autofocus even with an f/1.2 lens because the subject matter has very low contrast. I think the f/1.8 lens would have higher contrast which leads to better autofocusing. I am also concerned that the f1.2/85mm or f1.4/35mm will autofocus slower than the f/1.8 and f/2 alternatives. Could you tell me which lenses will autofocus faster and more accurately between lenses have a larger f-stop vs. lower f-stop, please?

When it comes to AF speed in low light, the first issue is whether the camera can autofocus at all without a focusing aid such as an AF Assist beam. If it can, then differences in AF speed (without the AF Assist beam) are going to be affected primarily by differences in lens design. Generally speaking, lenses with a rear-focus optical design, such as the EF85mm f/1.8 USM, are going to autofocus faster than lenses that move their entire optical formula, such as the EF85mm f/1.2L II USM. In that particular comparison, the difference in maximum aperture is irrelevant. In the case of EF35mm f/1.4L USM vs. EF 35mm f/2, both lenses have similar AF speed despite differences in focusing systems, so there's no particular advantage to one lens or the other in the specific area of low-light autofocus performance.... (emphasis mine)

http://www.digitaljournalist.org/issue0708/tech-tips.html

there are some other articles I can't find. Basically, all that happens with the extra-sensitive point is that the camera will autofocus to with a precision of 1/3 of DoF, rather than within DoF.

[dannequin]

Would the 40D have a better AF system for lowlight?

[dle42]

Would the 40D have a better AF system for lowlight?

Yes; for one, it has the special center point for f/2.8 lenses that came along since the 20D, IIRC. Also, I believe the outside points are all cross-type, so they are quicker to focus (in case you use anything other than the center point).

[Rudeofus]

Apart from the fact that it lets more light into the camera. Which will improve AF.

Into the camera, onto your sensor, but not to the AF sensor. The AF sensor has no idea your lens is any wider and performs exactly the same. For most cases this also applies to the view finder image: unless you have special focussing screens which do not come with your camera by default, you see the exact same image regardless of how much faster than F/2.8 your lens may be.

[RDKirk]

A greater amount of light striking the AF sensors does permit faster calculation of exposure, and because every system has a lower EV limit, a faster lens extends that limit to dimmer light (ISO and shutter speed being equal).

The AF accuracy tolerances, however, do not improve above f/2.8, which is when the camera turns on the high-precision algorithm.

Using the camera in extremely dim light, you have to use the same techniques we used with split image rangefinders in the manual-focus days. Find clear linear contrasts in the subject close to the intended focus point and focus on them.

Frequently, if you focus manually close to the intended subject, the autofocus system can grab it even if it could not focus from an extreme OOF position.