Low light focus performance

The faster the lens, the lower the light in which you can get good AF. However ALL cameras have some light limit below which AF becomes unreliable. You could try mounting a flash and letting it use its AF assist illuminator.

You might actually have gotten better results with the 40D since it has built in AF assist illumination!

"I've heard the 50 1.2 is soft" - who have you been listening to?

I knew the faster aperture lenses would be better in low light. Its why I switched to it outside. But I was asking is a 2.8 lens unreasonable indoors in the enviorment I desribed. Is it common for the guys who shoot these reg. to bypass the 2.8 in favor for the xtreme apertures or are they getting reasonable reliability with 2.8 and I have a malfunctioning camera. Was I setting myself up to fail the minute I mounted the lens.

I did use my speedlight and its AF beams. And it was still hunting. From the sound of your response, I was getting the best money could buy for the enviornment I was in.
>>"I've heard the 50 1.2 is soft" - who have you been listening to?

Internet pixel peepers. Same crap I read about the 85 f1.2L being soft at 1.2. Until I used one myself and witnessed how damn sharp it was wide open. I assumed most of it was unreasonable expectations. Some of those guys get crazy about lenses that arent as sharp wide open as 300 f2.8L wide open. Just unreasonable from a $1000 lens. I suspected it(50 f1.2) would perform well if in focus. As I stated above. I'd rather have a soft 50 1.2 image than an unusable OOF from anything else.

Sounds like I blew it. I should have went with the 50 all along. Still like to hear from those who shoot this stuff and the lenses they like ie 24 f1.4 etc.

Thanks

While the D3 and Nikon both have a reputation for better autofocusing, I doubt it would have helped you. If you were trying to autofocus without focus assist, and if you didn't use One Shot, center focus point (with focus assist), you will not get consistent autofocus in really dim conditions, even with wider aperture lenses. The cost of the camera has no bearing on this.

I gather you had some kind of external flash, since you mentioned bouncing a flash. There are ways to set up an external flash so you have focus assist but the flash doesn't fire (you can also use an ST-E2 for focus assist alone), although I don't know why you didn't use flash inside. That's what most wedding photographers do for truly dim lighting at wedding receptions. Some will use high ISO--3200 and 6400--without flash, but I bet they are still using focus assist of some kind.

If you used focus assist, it doesn't sound right that the camera hunted. I use a Tamron 28-75mm f2.8--not even a Canon lens--and with focus assist, it pretty much gets focus every time. You sure you were on One Shot, center focus point? If not on One Shot, you didn't get focus assist.

The 24-70mm has been known to have slippery autofocus/back/front focus issues, but if you don't notice bad autofocus in other situations, that isn't it.

I'd echo using one shot with the center focus point selected. Using Servo AF or allowing the camera to chose the AF point is probably asking for trouble in low light.

It's impossible to say whether an f2.8 lens is unreasonable indoors without knowing what the light levels were but I'd certainly expect AF to be fine (though maybe a little slow) under nomal "domestic" indoor lighting levels.

Were you getting AF confirmation signals ("beep", and or green dot illumination and/or AF zone lighting up)?

Thanks Nadine. I did use flash. Though I never knew the Af assist did not work in AI Servo. I thought it would not fire if it was too far away, but not at all. This is a representation of how dark it was. I was at f2.8 ISO 1600 and Manual Exp ranging depending on where I was. About 125th or so. I used the flash for everyshot last night always bouncing on anything I could find. Behind me, wall next to me, an umbrella next to me(the ones in the tables outside). Anything I could find to stop direct flash. This part was good.

I used Ai Servo most of the night until I went outide where I mounted the 50 1.8 and switch to One Shot because it doesnt work well with servo. I dont know why I didnt switch to one shot inside. I knew it would have a hard time in Servo in this low of light. I used all the selectable points through the night so I wasnt doing much recomposing. The Mark 3 doesnt matter about the center point. All of the ones I selected were cross type to f2.8. I guess switching slipped my mind as there was always people moving around and asking for pictures. Pretty busy all night.

I mean half the light of any wedding I've ever been to. But even in Ai Servo, I had instances where this thing would rack the lens back/forth from Macro to infinity looking for anything. Even one shot would have been no better there. But I guess if it was that bad, no camera could have focused.

Sounds like I had some bad judgment calls on some choices. When you are hired to do a job and you arrive and they've stolen all your light, you sort of go into survival mode in trying to get any shot at all and thinking of the little things to add up to a helpfull amount seem to land in the back of your mind.
Live and learn I guess. These little experiences will definitley stay with me. As I said, I never worked in this little light. I've had it bad before, but this was not meant to be. I took a camera reading in the middle with an expo at ISO 1600 f2.8 and 1/10th. I've done some shutter dragging but wasnt willing to drag that much. I could have jumped to 3200, but I'm stingy and the exposures were good where I was, just the lack of focus accuracy.

I think using the 50 and One Shot most of the night would have saved me probably another 30 shots.

Nadine, do you shoot these much. What lenses do you like and work well for the room sizes. I couldnt have imagined this enviorment at a wedding I was shooting where it really really matters

I never allow the camera to choose my focus point. I was selecting the 19 selectable throughout the night. The 19 are all crosstype to f2.8 so center point shouldnt have been needed.

Yes I was getting confirmation, but it was confirmed on other areas or no where at all. Seemed nothing in the image was sharp. Slow isn the word for it. I get the feeling I was really pushing the camera and lens to do something that was impossible in most cases. I guess I just got used to my equipment and started getting unreasonable in expectations. After a while you expect the equipment to do everything anytime anywhere when it just isnt possible. I guess I could have tried to MF. Probably been just as quick. LOL. I wasnt doing any speed shooting in there anyway. I guess I didnt do my job by taking over when the camera lost its way in Auto pilot huh.

ISO1600 f2.8 and 1/10th with expo disc was average. Pretty low.

Oh yeah Nadine, forgot. I have the 24-70 dialed in with Micro Adjustment on the body.

David--if you were in AI Servo, you were not getting ANY focus assist. So indoors, where you were in AI Servo, it was as if you were autofocusing with only the camera's autofocus system, which will definitely hunt in really dim lighting. You need to be in One Shot for the focus assist to even come on. So One Shot isn't better than AI Servo just by itself, no, but it is when you consider that you need it for focus assist to function. There is much of the problem, I think.

As Bob says, it is good to use center focus point even though your other points are cross type. I heard, because I don't have a 1DMkIII, that the center is still the most sensitive. And definitely pick your points, don't use auto focus points.

When I shoot wedding receptions, even outside at night with very little light, I use One Shot, focus assist, center focus point and other focus techniques to give myself margins of error. Not using wide open apertures is one, so dragging the shutter becomes important. There is also manual, zone focus for really, really dark conditions if even focus assist fails. I rarely go above ISO 1600, if that. I stay mostly around ISO 800. I use my Tamron zoom on my 5D. I sometimes use one of my tele primes, but mostly, it is the zoom for receptions. I also use off camera flashes, though, most of the time.