Bizarre 7d Continuous shooting speed variation

Ok new 7d owners, I want you to try something out here. I have confirmed that this happens on at least one other 7d apart from my own. Once you have tried it, does anyone have any idea WHY?? it does it.

So...put the camera in high continuous mode. ONE SHOT FOCUS Put it in TV mode and set a reasonably fast shutter speed so that you can get 8fps. Pull the trigger and let 'er fly. It will rattle along at 8fps. Now put your hand in front of the lens or swing it round to point at a dark area in your house or something. All of a sudden the shooting speed drops!

Now this is in one shot focus so there is no focusing going on to slow it down. This had me puzzled. So i tried it in manual exposure mode. Same thing!! In manual mode, the camera should surely just rattle off the frames without thinking, doesnt matter if they are correctly exposed?!?

So i tried a few different settings and found out that you can stop this by using the AE lock button ( or setting AE lock to the shutter button)

So this would indicate that something in the exposure system is causing the slowdown. Once locked to the exposure using the AE button it works. In which case why does it do it in Manual mode?? In manual mode the AE lock button does not function so there seems to be no way of preventing it happening in M.

It also does the same thing if you switch the auto focus OFF on your lens. Seemingly ruling any weird focus things out.

I looked in the manual. Indeed there is a note at the bottom of the page about continuous shooting stating that the speed may vary in dark rooms. But it offers no explanation, and I dont remember this being a factor in any of my previous cameras. I just tried my 5dII and it certainly doesnt behave in the same way.

I know the likelihood of this ever making any difference to me is slim but I just wanted to know why id does it??

It also varies depending which lens you use. Sticking an f4 lens on it makes it considerably more susceptible. Even when shot at equivalent apertures. I put my 50mm 1.8 on the camera and aimed it at a dark corner of my room but set the aperture to f4 and achieved a much faster shooting rate than i did with my 24-105 f4 even though i was shooting in MANUAL exposure mode.

EDIT:: See my post below. It is NOT something to do with Custom Functions as far as i can tell.

Is there a custom function for safety shift, i.e is it enabled and overruling the exposure when it is darker..?

What is the number in the VF? Does the buffer have plenty of room?
Also check out the CF mentioned above.
Does it try to refocus between shots because that could effect speed as well. Try it in manual exposure and Manual focus.

EDIT+*+* reread your post and saw that you set your lens to AF off. See if there is a custom function that hinders firing when focus is not obtained.

Neilyb wrote in post #8728480
Is there a custom function for safety shift, i.e is it enabled and overruling the exposure when it is darker..?

Either this or...

On the 1-series, you can tell the camera to favor focus over speed and it will slow the burst speed in an effort to try and ensure more frames will be properly focused.

If the AF on the 7D is based on the 1DMkIII, perhaps it's slowing the burst to give itself more time to focus?

FlyingPhotog wrote in post #8728521
Either this or...

On the 1-series, you can tell the camera to favor focus over speed and it will slow the burst speed in an effort to try and ensure more frames will be properly focused.

If the AF on the 7D is based on the 1DMkIII, perhaps it's slowing the burst to give itself more time to focus?

Yep, that makes sense. It's CF setting...

Yes a CF setting was the first thing i thought of. But all the CF settings are similar to the 1 series (which i also own so have experience with)

The settings you are thinking about are the same one the i thought would be the one to change too. It changes whether to favor shooting speed or focus accuracy and whether to still fire the shutter even if focus is not achieved.

BUT this CF is only valid when you are actually using AF. In my tests, the foucs was not seeking because it was switched off. And I also tried it in One shot mode. Again it obtains focus fine to begin with (VERYquickly i might add) and does not seek at all during continuous shooting and yet you still get the slow down.

There are no other Custom functions that would seem to be relevant. The fact that is is stopable by using the AE lock button is so weird.

Also , to answer one comment above. There is a safety shift function and it was set to OFF.

What about in Manual focus?

Yep , does exactly the same thing in manual focus as I mentioned.

I would call and ask Canon.
Since it mentioned it in the manual is there anything in the troubleshooting section in the manual?

You mentioned "manual exposure" which has nothing to do with manual focus.

EDIT: I misread

dandig wrote in post #8728829
Yes a CF setting was the first thing i thought of. But all the CF settings are similar to the 1 series (which i also own so have experience with)

The settings you are thinking about are the same one the i thought would be the one to change too. It changes whether to favor shooting speed or focus accuracy and whether to still fire the shutter even if focus is not achieved.

BUT this CF is only valid when you are actually using AF. In my tests, the foucs was not seeking because it was switched off. And I also tried it in One shot mode. Again it obtains focus fine to begin with (VERYquickly i might add) and does not seek at all during continuous shooting and yet you still get the slow down.

There are no other Custom functions that would seem to be relevant. The fact that is is stopable by using the AE lock button is so weird.

Also , to answer one comment above. There is a safety shift function and it was set to OFF.

Look at the shutter speeds it uses when taking these dark pictures. I willing to bet the shutter speeds are a lot slower. I'd bet you have "safety shift in Tv mode" enabled, which will do exactly what you are seeing.

^^^

dandig wrote in post #8728829
There is a safety shift function and it was set to OFF.

Nope, i checked that too. The shutter speed is always exactly the same. If i set it to 1/1000 it stays at that speed even when the continuous shoot speed is slowing, its still at 1/1000.

Like i said, its mentioned in the manual , as a footnote on one of the pages. And I also had someone else with a 7d see if theirs did the same thing and they confirmed that it did..... which is very odd...

dandig wrote in post #8728212
Ok new 7d owners, I want you to try something out here. I have confirmed that this happens on at least one other 7d apart from my own. Once you have tried it, does anyone have any idea WHY?? it does it.

So...put the camera in high continuous mode. ONE SHOT FOCUS Put it in TV mode and set a reasonably fast shutter speed so that you can get 8fps. Pull the trigger and let 'er fly. It will rattle along at 8fps. Now put your hand in front of the lens or swing it round to point at a dark area in your house or something. All of a sudden the shooting speed drops!

Now this is in one shot focus so there is no focusing going on to slow it down. This had me puzzled. So i tried it in manual exposure mode. Same thing!! In manual mode, the camera should surely just rattle off the frames without thinking, doesnt matter if they are correctly exposed?!?

So i tried a few different settings and found out that you can stop this by using the AE lock button ( or setting AE lock to the shutter button)

So this would indicate that something in the exposure system is causing the slowdown. Once locked to the exposure using the AE button it works. In which case why does it do it in Manual mode?? In manual mode the AE lock button does not function so there seems to be no way of preventing it happening in M.

It also does the same thing if you switch the auto focus OFF on your lens. Seemingly ruling any weird focus things out.

I looked in the manual. Indeed there is a note at the bottom of the page about continuous shooting stating that the speed may vary in dark rooms. But it offers no explanation, and I dont remember this being a factor in any of my previous cameras. I just tried my 5dII and it certainly doesnt behave in the same way.

I know the likelihood of this ever making any difference to me is slim but I just wanted to know why id does it??

It also varies depending which lens you use. Sticking an f4 lens on it makes it considerably more susceptible. Even when shot at equivalent apertures. I put my 50mm 1.8 on the camera and aimed it at a dark corner of my room but set the aperture to f4 and achieved a much faster shooting rate than i did with my 24-105 f4 even though i was shooting in MANUAL exposure mode.

EDIT:: See my post below. It is NOT something to do with Custom Functions as far as i can tell.

It usually refers to the fact that noisier pictures take a lot more bytes to store. For instance, in the 50D, the RAW file size can go from 18Mbytes (at ISO100) to almost 30Mbytes (at ISO12800), and so the camera has to move larger files but, as it has only a certain mbps capability, the frame rate suffers .

Miguel

Was your ISO set to "Auto"? On page 63 of the manual, it seems to indicate that when the ISO is set to "Auto", the ISO will vary from 100-3200, in the green box, CA, P, Tv, Av, and M shooting modes. If it is, then my next question would be, is your High ISO Noise Reduction turned on in the CFunctions (actually, this alone may be the culprit if it is on)