Ai Servo in low light

[Viggo]

Hi guys!

I'm think I will end up in straight-jacket soon. I've been trying to get lowlight images to focus properly, but it doesn't. I'm talking about normal indoor light , not anything crazy dark. If it's pitch black One Shot will work, but I'm dependent on Ai Servo. But still or not still subjects, it's just random if anything is in focus.

I use a 1d mkIV and 24 L II, 50 f1,2 L and the 50 is better, but not exactly perfect, my 85 1,2 II is to slow to miss or just to slow to hit.

Every lens is calibrated and they have been microadjusted to hit properly, and they all do, in good light.

QUESTION: Has anyone heard of any low light problems with the mkIV, I haven't... Or if anyone knows and have tried any settings that would work better.?

I feel I have tried every combinations of settings possible, but maybe not?

I mean what's the point in having super clean 3200 iso and an f1,4 or 1,2 lens when it doesn't focus in light lower than that I could use a 2,8??

Thanks!

 

[gbaturin]

Canon's AI servo is still rather poor, I'm afraid =( I tried it on my 50D, but quickly gave up - it's too damn slow. Maybe the 7D is better, I don't know, never tried it.

 

[leGreve]

Yeah... Although I love Canon, the very low light exposures, with little time to shoot, are hard to do. So if that is one of your main things to do, I could see the problem, but I would probably compensate with an EX flash or similar to fill the room.

 

[Loswr]

but I would probably compensate with an EX flash or similar to fill the room.

Compensate for what? I think the issue at hand is the autofocus in low light, not the exposure/image in low light. The AF assist lamp on external speedlites does not operate in AI Servo mode.

Viggo, how are you at manual focus? One option would be to use MF with a brighter focusing screen like the Ec-S or the Brightscreen p222.

 

[Admin US West]

The 1D MK IV is well known for its weak low light focusing. The 5D MK II is about the best. Attach a flash unit (580 EX II) which has a focus assist light. That will be about the best solution.

 

[hlphoto]

The 1D MK IV is well known for its weak low light focusing. The 5D MK II is about the best. Attach a flash unit (580 EX II) which has a focus assist light. That will be about the best solution.

Realise that focus assist will only work in one shot and AI Focus modes (and I'm not even sure about AI Focus, since I always use one shot in these situations).

 

[Admin US West]

Realise that focus assist will only work in one shot and AI Focus modes (and I'm not even sure about AI Focus, since I always use one shot in these situations).
[/quote]

Can you provide a reference that says this?

When the external flash is enabled, AF Assist is automatic on the 1D MK IV. It can be disabled by CFNIII-15, and it is not available in live view under certain conditions.

See pg 98, 119, 134, 216, 225 of the manual.

 

[hlphoto]

Are you sure? >> I don't own the 1D Mk4, do my work mostly with 5D-bodies and sometimes add in a borrowed 1D for sports and as a backup for videojobs. Both 5D's don't let me use the AF Assist during AI Servo focusing, only on one shot and maybe (never tested) AI focus.
I thought I had seen the 1D Mk4 perform the exact same behaviour.

Edit: Just checked, can't find anything about the focus-beam not emitting but also nothing that says it will do so while in AI Servo. I know I have been troubled by this not happening in dark situations (with both 5D bodies and my former 30D and 50D's) before so if someone can tell me how to get it to work, I'm looking forward to it.
Also found out the 1D Mk4 doesn't even have AI Focus, which says something about how much I use AI Focus to start with (only AI Servo and One Shot)

 

[Loswr]

Can you provide a reference that says this?

Sure, you can reference my post above, where I stated, "The AF assist lamp on external speedlites does not operate in AI Servo mode."



Seriously, though, have you tried it and found it to work? I know empirically that on my 5DII and 7D, the AF assist beam will not fire in AI Servo, and there are plenty of reports across the forums that this is true for other models including the 1DIV.

Recent Canon literature ignores the issue completely, but if you go back to the 30D white paper, there's a statement that, "ONE-SHOT AF is recommended for flash photography because the AF-assist beam cannot match predictive AI SERVO AF." The AF assist beam is essentially unchanged since the then-current Speedlites, but AI Servo has improved substantially. So, if the AF Assist couldn't keep up with the older 30D's AI Servo, it certainly can't keep up with newer ones...

 

[revup67]

Though this response is related though I won't touch the AI Servo as Neuro already covered this, in using the MP-E 65 yesterday without the flash at F11 it was complete darkness both in Live View and VF. As soon as I mounted the MT 24EX macro flash in E-TTL I had light in Live View and was able to focus. I would imagine the same would be true with the 580 EXII or similar E-TTL flashes so that in fact that may aid your situation especially if in Live View as I was able to at the very least manual focus in low light.

 

[Admin US West]

Can you provide a reference that says this?

Sure, you can reference my post above, where I stated, "The AF assist lamp on external speedlites does not operate in AI Servo mode."

You are right, I tried it just now. One Shot and AI Focus use the AF-Assist light, but AI Servo disables it.

I guess its never too late to learn something new.

I'm going to be doing a lot of very low light photography at a upcoming theatre event, However, I'll be using my 5d MK II without flash, and its never failed to AF in low light using center point and one shot.

 

[Viggo]

Thanks guys, but yeah no, the AF-assist is only in one shot, no question.

Manual focus isn't an option, and neither is One Shot. It can be absolutely PITCH BLACK and the One Shot focus will lock without any problem with any of my lenses.

The problem is the Ai Servo tracking abilities. Ai Focus doesn't exist on the mkIV.

I know one thing that would help matters a great deal, if Canon could release a firmware that would enable Spot-AF with all lenses, not only the super-tele's with the AF-button on the lens itself. They did with a 7D, give it to me also!!

 

[Viggo]

*Update*

I tried sitting the camera on a tripod, plenty of light and an easy to focus on subject (in Ai Servo). It locks on, but then in tiny steps just go back and forth trying to re-focus all the time, it's just pure luck to hit it right at larger apertures.

Tried the same thing with my gf's 5d2, and when it locks, it doesn't move AT ALL, so I can sit there and wait for hours without it trying to re focus, and it everything is in focus when I decide to hit the button.

I think the focusing points are just to big on the mkIV, so it get's info to the same point from different depths.

Needless to say, I'm very frustrated and dissapointed (especially since I had a very early edition mkIII which was USELESS!)

 

[outsider]

Plagued by the same restriction of not being able to continuously focus in really low light, I hacked together something that removed that limitation.
Since the limitation is in the flash/AF assist light (and not so much the camera's AF abilities), I built my own AF assist light.
It's essentially a laser pointer triggered by a momentary push button.

Details can be found on my blog at
http://adrian.onsen.ca/2011/05/af-assist-tool-version-1-0/

I'd be interested to hear your thoughts.

 

[motorhead]

I assume everyone is aware that AI Servo is not designed to achieve a confirmed focus lock? If thats whats needed then AI Servo is not the right tool for the job.

Instead it is designed to do the best it can in the time before the shutter is released. So there are bound to be high failure rates when conditions are not good, low light certainly qualifies as one such.