1D MKIII AF - How Dark Till No AF?

How dark does it need to be before the 1D MKIII AF stops being effective?

I had to use Live View to MF while I was shooting with a 35L in a bar, and my images show pretty clean exposure with... But again, my autofocus wasn't able to lock.
f1.6
ISO 3200
Shutter Speed 1/25

PS, even at those extremes the images look so clean! I love this camera!

Baaah, could someone mov this to EOS Cameras forum?

I don't know about the 1d3 but the 5D2 is terrible in this regard, it's less sensitive than even the 40D

If you know how to use a split-image rangefinder, you can extend useful focusing of even a 5D to as low as you can physically see.

Yeah. After the night at the bar I've been considering a katz split prism. Maybe even a oem canon focus screen.

Don't know about one shot, but ai servo craps out at about f2.8 iso3200 1/30... but then again, you really don't need tracking when the shutter is that slow, any subject movement after the shutter goes will give you blur, and ai servo can't adjust to that.

drPheta wrote in post #7580767
Yeah. After the night at the bar I've been considering a katz split prism. Maybe even a oem canon focus screen.

No, I'm talking about using split-image rangefinder techniques with the Canon autofocus system. If you use the same technques, you can get the AF system to outperform an optical split image rangefinder in dim light.

drPheta wrote in post #7577911
How dark does it need to be before the 1D MKIII AF stops being effective?

I had to use Live View to MF while I was shooting with a 35L in a bar, and my images show pretty clean exposure with... But again, my autofocus wasn't able to lock.
f1.6
ISO 3200
Shutter Speed 1/25

PS, even at those extremes the images look so clean! I love this camera!

Its autofocused for me in darker conditions. Are you AFing on a point that has some contrast?

The 1D MK3 is by far the best low light AF camera I've ever used. 2nd place was the 20D, followed by the 1D MK2 and 1D MK2N, and 300D. The improvement from the MK2's to the MK3 is very noticeable. I've also used the D3 (with 24-70) and D700 (with 70-200VR) in relatively low light at Henry's (camera store), and while they were very quick cameras, my 1D MK3 locked focus noticeably faster than both of those (I would put those cameras at slightly faster than the 20D).

I shoot primarily low light, and the best example was at a nightclub for a fundraiser in January. Average shots were about 1/25s at F2.8 and ISO3200 (some were much lower), and the camera was instant (using the 24-70L and 70-200/2.8L IS). I used selected focus points, not always center either. About half were taken using off center AF points.

Here is an example:
90mm, F2.8, ISO3200, 1/8s

130mm, F2.8, ISO3200, 1/40s

When my camera gets back from Canon with the recall fix, I will test it to see exactly how low it can go.
.

drisley wrote in post #7614970
The 1D MK3 is by far the best low light AF camera I've ever used. . .

Yes, I can accept all this, but I too am beginning to feel that the really low end is no longer performing, or performing as well as it was prior to the fix ~ still great IMO, and so far not a problem ~ I've not put this to the test, just an observation as the subject came up.

Gerbee, so you updated the firmware AND had the hardware fix?

See, that's the thing. I specifically remember my 1D being able to focus in low light with f1.4 (50mm 1.4 lens) down to pretty darned low. I don't recall it hunting, but after sending in to Canon this past month I can't get a lock on the conditions I posted on at the top.

FYI, here's what I'm talking about. These shots needed Live View

I'd imagine the eye area would be high contrast enough for low light focusing. But, even still I tried the shirts, jackets/skin interface, etc. I couldn't get a lock and had to use Live View.

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

drisley wrote in post #7615675
Gerbee, so you updated the firmware AND had the hardware fix?

Yes, I have and I'm pleased enough too. I would not have reported this low light observation, as it's still much better than the 1DMKIIn and goes without saying, than the 5D.

I've just 'tested' mine under EV 5/100ISO, low contrast subject ~ no difficulties using my 70~200mm ƒ2.8L that I normally use with it.

For my low low light stuff I take the camera off AI Servo and use One Shot - YMMV

This should be no contest for the 1DMKIII.

The second picture though, may be put off by the back lighting. This is something I find irritating with most Canon cameras actually, they do have a tendency to be disturbed by bright backgrounds.

drPheta wrote in post #7616161

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO