I have had my 7D for a couple of weeks and am generally happy with it. I just discovered today that it has one perplexing limitation.
It will shoot at 8FPS quite nicely until you get below a certain amount of ambient light. Not exposure, but ambient light. I am sure this also relates to maximum aperture of the lens too. As soon as the light falls below the equivalent of 3200ISO, 1/100 and f2.8, the frame rate drops. This happens in normal view. If the camera is set to live view and continuous shots are taken it stays steady no matter what the ambient light is. This tested in manual mode where the camera has to do no thinking.
I am quite surprised by this as my 40D and my 20D do not exhibit this behavior. They both hold on to their maximum frame rate no matter what the light. Yes, I have disabled all the auto processing in the 7D, and yes I have gone over every setting to make sure there isn't anything to interfere.
So I went looking and sure enough, page 93 of the manual, last footnote:
"In low-light areas or indoors, the continuous shooting speed may become slower even if a fast shutter speed is set."
Gil_W wrote:
High ISO speed noise reduction probably. There is a CF for that too, which you can disable.
If that doesn't do the trick, then we need to convince Tramm Hudson to hurry up and port "Magic Lantern" from the 5Dmk2 to the 7D. That could be one of the many "requirements" for such a firmware update.
Was your lens set to AF when the fps dropped? And do you have your CFs set to give priority to focus? Any conditions that reduce focus time will also reduce fps. And this is true with every body, not just the 7D.
I don't have a 7D, mine is on order, though I've looked at the manual. See page 93 (at the bottom) where it mentions that low light can effect shooting speed.
So you're saying that with settings that make it impossible for the camera to have any idea of, or be affected by ambient light (not metering, not focusing), somehow the camera knows when the light is low? Does this happen no matter the ISO? If you don't have a lens attached, cap off, camera in high-speed shutter mode, M mode with fast shutter speed, you press on the shutter and fps is reduced as you walk from a well-lit room in to a closet? Like there's a sensor on the camera that's independent of all other functions?
No Russ. It appears that the total EV entering the camera is responsible. If the light entering the camera drops below proper exposure for ISO3200, 1/100 and f2.8, then the number of shots per second starts to drop. All auto settings off, fully manual exposure, and no focusing going on. Moving the camera from dark to light areas while running causes the frame rate to go up and going into a dark area makes it drop. All of this in what is fully manual operation.
The same thing does not happen with the 20D nor the 40D. They hold on to their maximum frame rate no matter what.
It does not make sense that the camera has to do this. What this implies is that if you want to do high speed frames in darker situations you might be out of luck and the 40D will do better!
Interesting, but I don't have an answer.
In AF mode I'd see the camera limiting max FPS in low light. (Yet, shouldn't one have the ability to override AF by enabling the drive priority ?)
However, you are saying you lose FPS in manual mode. Could be a firmware glitch ?
Petkal, I don't know what the reason is. It is mentioned as a cryptic footnote in the manual. And as I said, the limitation goes away in live view mode!
Fascinating. And weird. So what's the tecnhical difference with live view that eliminates the phenomenon? (Of course if you knew that, you wouldn't have posted!)
I might hazard a guess that the new fangled exposure meter array and/or the new fangled focusing array are still active and holding things up even though it is set to fully manual. Putting the camera in live view takes them off line because the mirror is up and they lose their view. So if I am right, there is no reason for this to happen because if the arrays can be disabled with live view, they should be able to be shut down and ignored in normal mode.
In one of the other 7D discussions here someone commented that it's due to the new metering system. Whether or not that is fact remains to be seen... Maybe Chuck Westfall will clarify this in his monthly column for the Digital Journalist if someone takes the time to submit the question.
It probably has to do with the shutter speed. Below a certain threshold, the framerate must slow down. It takes time to cycle the mirror/shutter between frames.
And this has nothing to do with the shutter speed - IE: like the 40D's 6.5, than falters as the SS slows (obviously, since you cant make 6fps @ 1/15th of a second)
