7D high speed continuous shot problem

[Mark1616]

There is something weird going on with my 7D when shooting in high speed continuous drive.

Basically in low light/under exposed situations it will not hit the 8fps, probably not even making 4fps.

To test this I've gone for manual focus (takes out any focus release issues), manual exposure so shutter speed is up over 1/2000s so can attain the 8fps and then shot. If I point at a correctly exposed or over exposed area then it will fire off as expected, if then somewhere less bright it will slow the shooting right down.

I've tried a settings reset to make sure nothing funny is going on but still no joy.

Any ideas?

[schent1]

I have noticed a slow down at time too. Thought it was related to focus as it has happened to me in good light on occasion. I have not done any test so you are ahead of me on this one.

[JustinThyme]

Ahh....a victim of marketing.
A couple of things here Mark. Firstly the cameras processor is slowed by shooting low light high ISO and if you have NR turned on its slowed even more. The 7D has a single digicIV processor where as the 1D IV has dual digic IVs. Secondly If you compare file sizes you will see the low light high ISO images are much larger than the good lighting low ISO images so your buffer fills up faster and the write time takes longer but this would be more likley seen as shorter bursts counts. If you need speed in low light try a smaller jpeg size and turn off NR. You will just have to do NR in post process.

[shadokachr]

Actually the 7D has dual Digic IV processors. Low light image files contain more black areas and create a larger more dense file. Also if the highlight tone priority is activated it can and will slow it down as well. Finally, the cf card read-write speed is also a factor.

[JimC]

As JustinThyme mentioned, NR settings might be slowing it down, as those settings do have a big impact with some Canon models.

For example, if you look at the Canon T2i review at dpreview.com, they measured a max frame rate of 2.5fps shooting jpeg fine with NR set to Strong, whereas that camera was able to shoot at 3.7fps with NR turned off.

http://www.dpreview.com/reviews/canoneos550d/page12.asp

But, they didn't publish their 7D tests both ways. So, you'll have to see what you get using different NR settings to find out if that could be the culprit or not.

[JustinThyme]

Originally Posted by shadokachr

Actually the 7D has dual Digic IV processors. Low light image files contain more black areas and create a larger more dense file. Also if the highlight tone priority is activated it can and will slow it down as well. Finally, the cf card read-write speed is also a factor.

Thanks for pointing that out!

That would certainly explain why it can get 8FPS

Concession its not the processor so it leaves the rest and as noted above if you are using slow CF (not that you would) in these days of speed and UDMA it could slow it down just because of the larger images.

[Mark1616]

It is just a feature of the camera, no anything to do with settings (I don't use highlight tome priority or in camera noise reduction and have 60mb/s cards). There is loads about this happening all over the web so I'm stuck with it. It really doesn't affect real world shooting apart from low light flash with high fps.

[wave01]

Hi from what you say it is low light plus flash. I assume you use external. My thoughts firmware issue it may just be waiting for a flash to charge, it may think its using an internal one which is why I say firmware issue

[Mark1616]

The flash part was just an example of the only time when this slow down might get in the way of shooting a sequence where I want high speed rather than being the only te it occurs. Also the camera doesn't wait for the flash to charge, it will shoot away no matter if the flash fires or not. I will try to word what I meant again. As this 'feature' of the 7D only has an effect in low ambient light then normally those are not situations where I would want the high speed continuous shooting as shutter speed would be down so not doing sports etc, it is only some cases where I'm using flash that I might desire a fast burst and with the 7D that isn't possible. It's fine now that I know this isn't a camera fault so I'm not too concerned.