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Gear Talk => Technical Support => Topic started by: AdamJ on September 12, 2012, 12:20:39 AM

Title: 24-105 / 7D slow burst rate
Post by: AdamJ on September 12, 2012, 12:20:39 AM
I've noticed that, in "Hi" mode, my 7D often won't fire at 8 fps with my 24-105 L attached. Other times it will. When it won't, it fires at about 3-4 fps. I've already established that it has nothing to do with the shutter speed being too slow. Also, none of my other lenses causes this behaviour.

I'm guessing that the diaphragm blades in the lens might somehow be "sticky" but it's only a guess. The lens is six years old so I suppose it has had plenty of time to develop some kind of problem like this. Does anyone else have any ideas?
Title: Re: 24-105 / 7D slow burst rate
Post by: neuroanatomist on September 12, 2012, 08:15:14 AM
Low light?  The frame rate drops to ~4 fps in low light (which supposedly allows time for accurate metering).

My 7D + 24-105L delivers 8 fps in good light.
Title: Re: 24-105 / 7D slow burst rate
Post by: AdamJ on September 12, 2012, 11:40:10 AM
Ah, that might be it - thanks Neuro. Having tested it in manual with a fast shutter speed, metering speed didn't occur to me as a factor. I'll check it again later.
Title: Re: 24-105 / 7D slow burst rate
Post by: RuneL on September 12, 2012, 07:34:10 PM
You can also setup (at least on the 1D's) if drive, AF or tracking has priority when shooting continuously.
Title: Re: 24-105 / 7D slow burst rate
Post by: dr croubie on September 12, 2012, 11:58:39 PM
Also, i've been reading mutterings around here that if you've got the v2 firmware, and you're in AI Servo, you only get 4fps. I can't confirm because i'm still to update mine. What firmware have you got?
Title: Re: 24-105 / 7D slow burst rate
Post by: Richard Lane on September 13, 2012, 08:42:45 AM
The decreased frame rate has nothing to do with the new 2.0 firmware update.  The 7D has behaved this way since its introduction.

As Neuro has pointed out, the 7D will decrease its frame rate in half, in low light in order to aid in metering.  It will do this in AV, TV and Manual mode.  In AV and TV if you lock exposure with AE Lock it will maintain 8fps.  For some strange reason, in manual mode and auto ISO or fixed ISO, which technically it is locking exposure, the 7D will still cut its frame rate in half in low light.

There are 3 workarounds to maintain 8fps:
1) using AE* lock in AV and TV
2) using live view
3) pressing the DOF preview button simultaneously while shooting in manual

Unfortunately, none of these techniques are too practical or beneficial, because generally if the light is so low that the frame rate is cut in half, then your exposures will probably be too dark anyway.  However, I have experienced this frame rate drop at dusk while shooting a bird in flight, flying low over the water of a dark lake, and occasionally with night sports in poorly lit portions of the filed, like the end zone. 

This was one of the main reasons that I upgraded to the MKIV, as I wasn't sure if the 7D was intentionally crippled by Canon.

So Adam, it's not your lens, however slower lenses in low light will accentuate the problem.

Rich