Is it normal for the burst rate to slow down when you stop down the aperture?

Praefos wrote:

Hi Guys,

I have the M3, M6 and M6 MkII. I also noticed the slow down. My reasoning is the following:

Every mirrorless camera (from Canon) will try to attempt auto focus wide open, because they get a cleaner image and the framerate, they can achieve, is higher.

When you actually take a shot, the camera has to adjust the aperture to your settings. This might result in a lag. This aperture lag is only part of a sum of different lags combined.

This lag consists of frame grap lag, AF lag and Aperture lag.

Frame grap lag is the time until the sensor has been exposed correctly in order to check for correct AF.

AF lag is the time until AF is achieved.

Aperture lag is the time until the aperture blade have been moved to the correct Position.

Usally the Frame grap lag is quite low, because the camera always uses the maximum aperture (low aperture number) to achieve a quick exposure of the sensor. This might not be true for dark situations.

The AF lag can be considered quite low and nearly constant as long as the camera has already achieved focus. This is especially true for manual focus (no AF) or continues AF (AF has probably already been achieved). If you're using a slow focusing lens or even a bright lens, this might be a big factor until you achieve focus.

Aperture lag is inherintly a logical occurance within mirrorless cameras (and maybe DSLR in live mode), because the camera has to close down the aperture blades and has to wait some milliseconds. This can depend strongly on the lens and it's response time to the camera commands and the communication speed throught its mount system.

Possible fix through Canon:

Canon could fix this situation by offering a mode, which actually closes the aperture to the set aperture number and doesn't use the maximum aperture for AF all the time. This will prevent the aperture lag from occuring.

I have and used a couple of MF lenses. Those lenses will always give you the right depth of field preview, because the camera cannot control the aperture. This also means, it will not suffer from AF lag or aperture lag, resulting in a maximum burst rate.

It will suffer from frame grap lag. This can be a negative and a positive side effect. Due to high ISO during manual focusing, you might see your subject very noisy. But you will notice a drop in framerate and thisshould tell you to open up your aperture blades.

Side note: With this mode your focus point might not always be in the middle your depth of field.

This is all well and good, however it doesn’t explain why this slowdown only happens on  adapted  lenses, and not native EF-M lenses.  Something else is at work here.

R2