1d Mark IV Drive Speed

jase1125 wrote in post #15294523
That is what I am trying to figure out

Which CF's are you actually changing.

convergent wrote in post #15288694
Having spent many years working in electronics, it makes no sense (to me) that the body would slow down.

vvvvvv

jase1125 wrote in post #15288974
Takes a good bit of juice to drive the shutter mechanism at full frame rate, capture the image, process it, write to the card and drive the lens motor I suppose. Anyway, I am still trying to uncover the mystery of mine.

^^^^^^ yep

The body slows down because the software tells it to slow down. It's not slowing because of analog influences in the way a motor will slow down. In testing, Canon surely found that the camera becomes unreliable when there is not as much power available, and that slowing the FPS is likely the easiest way to make it reliable again.

Oh but it does. The mirror and shutter mechanisms are driven by motors. If the supply voltage for these motors is reduced, then they can't perform at their max capacity. The motors may be controlled by electronics that's digital by nature, but the conversion of current to magnetism in the windings is as analog as it has ever been, and it's very sensitive to which voltage you apply.

For the simplest motors (like DC PM motors), speed is directly proportional to voltage and torque to current.

apersson850 wrote in post #15294820
Oh but it does. The mirror and shutter mechanisms are driven by motors. If the supply voltage for these motors is reduced, then they can't perform at their max capacity. The motors may be controlled by electronics that's digital by nature, but the conversion of current to magnetism in the windings is as analog as it has ever been, and it's very sensitive to which voltage you apply.

For the simplest motors (like DC PM motors), speed is directly proportional to voltage and torque to current.

Are you suggesting that the camera decides a specific curtain separation for every shot to compensate for the speed they travel? During a long burst, the battery would see more drain, and the curtains would travel slower, so they would need to be closer together to maintain the exposure, right?

My bet would be that the shutter system is receiving a controlled voltage so they always function the same. The power drop would then only require a lower frame rate to keep the shutter running at spec.

The shutter itself is not affected. Exposure is the same. It's the re-arming of the shutter between shots, as well as the mirror movement (and film transport in old days' cameras) that's affected by the reduced supply voltage. I'm not sure how they do today, but in the old days, the specific movements of the shutter curtains was mechanically controlled, by springs, but cooking the springs between shots was electrically powered (in motorized cameras).

It could be that the shutter itself is also motorized today, but the pictures I've seen look more like the release of the curtains is electromagnetic, but the movement is by some spring, which is pre-tensioned by a motor.

Not to be funny, but, by chance, could you have the FPS limited to 8 vs. the 10 standard? I know I have set my limit to 8, and clearing the CFs would change this back to 10.

apersson850 wrote in post #15294869
The shutter itself is not affected. Exposure is the same. It's the re-arming of the shutter between shots, as well as the mirror movement (and film transport in old days' cameras) that's affected by the reduced supply voltage. I'm not sure how they do today, but in the old days, the specific movements of the shutter curtains was mechanically controlled, by springs, but cooking the springs between shots was electrically powered (in motorized cameras).

It could be that the shutter itself is also motorized today, but the pictures I've seen look more like the release of the curtains is electromagnetic, but the movement is by some spring, which is pre-tensioned by a motor.

Makes sense, cool to think about designing that stuff.

So do you think then that the FPS drop is just because the camera senses that the springs aren't loaded or the electromagnet isn't ready? I think that loosely falls under my hypothesis that it's software slowing things down intentionally because of reliability issues, rather than blindly firing the shutter with less spring or magnetic power.

The other possibility is that the software assumes that there will be trouble (as above) at a certain power level, so it just pulls back the FPS to get out in front of it without needing as much sensor feedback from various systems.

The motors running the cooking of the mechanisms in the camera are brush-less motors. So Canon says in their brochures. Thus they must have commutation feedback of some kind, and that can also be used for position feedback. Hence the camera can measure the result of the motor's movement, and therefore knows when the motor has performed the number of turns it has to do to make the camera ready to shoot. When controlling servo motors, you can select to trip if the motor has come too far behing (following error too large), or you can select to wait until it reaches the proper position. Often a combination of both is implemented.

In a system like the one in a camera, the simplest is to run the motor as fast as possible, then just wait a little longer when the power available is weaker. The other two options would be to stop shooting when you can't keep speed up, which is a bad option for most users, or limit the max speed to something you can keep up even with a low battery, a compromise most wouldn't like either.

Multi-axis motor/motion control happens to be my profession - that's why I know a bit about these things. The principle is the same, even if they are in different types of devices.

Cool stuff, and makes sense.

High ISO noise reduction slows my 7D down, or is it the buffer, or something like that much help, i know.