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

I have a Canon M5, and I recently noticed that if I stop the aperture down, my max burst rate takes a pretty noticable hit, especially when using servo (continuous) autofocus (going from a max of 7FPS to around 4 or worse). It's a lot less noticable in one shot AF, but it does definitely slow down. It gets worse the more I stop down. I had a DSLR before and don't recall this ever happening. Is this an issue unique to the M5, or among mirrorless cameras of this price range? I can't come up with a logical reason as to why, since all cameras focus at the lens' max apertures anyways, and closing down the aperture is pretty much instantaneous.

PS: for those who are wondering, I was using an adapted EF Sigma lens, but this still happens with my Canon EF-M 15-45 as well, though curiously at a darker aperture than the Sigma.

What shutter speeds are you using? Stopping down the lens will slow the shutter speed, other things being equal.

Wintereater wrote:

I can't come up with a logical reason as to why, since all cameras focus at the lens' max apertures anyways

Not necessarily. Do you have Exposure Simulation enabled? At many exposure combinations the lens will indeed remain stopped down for (servo) autofocus! Just observe it. It’s possible that the AF is what’s slowing things down. Turn Exp. Simulation off and see what happens.

Let us know,

R2

I was shooting in full manual mode not aperture priority, so stopping down should not and did not change anything but the ISO which was set to auto (in any case, I was shooting at 1/1000th, so plenty fast enough to not slow the max burst rate). I also tried keeping ISO on manual as well and it still slowed down.

I turned off exp simulation, and it didn't fix it. However, I did discover something weird. So at max aperture (f/5.0 in my case), servo AF works as expected (7fps). Stopping down from 5.6-8.0 it slows way down (3-4fps), but from 9.0 and above, it quickens back up noticably (6 fps), although not to max speed. I'm so confused. I have every setting set to manual so I don't know what could possibly be changing.

Edit: after turning off my camera and on again, anything below max aperture resulted in the same, below max speed burst rate, but it was consistent at all apertures for some reason. I even turned off auto white balance but no change.

Also, if the exposure sim. and aperture thing were true, then the slowdown when using one-shot af shouldn't be happening.

Wintereater wrote:

I was shooting in full manual mode not aperture priority, so stopping down should not and did not change anything but the ISO which was set to auto (in any case, I was shooting at 1/1000th, so plenty fast enough to not slow the max burst rate). I also tried keeping ISO on manual as well and it still slowed down.

Bear in mind that generally higher ISO shots have larger file sizes, which may influence burst rate. So, stopping down will increase ISO (either on Auto or manually, assuming you adjusted the exposure to suit the slower aperture), which will generally increase file size.

I cannot explain why it would speed back up at f9 though ?

Do you have continuous AF (different to servo AF) turned on ? That may be trying to focus between shots even if on One Shot ?

It could be a 3rd party lens peculiarity ? Since your 15-45mm behaves differently, it may be a combination of things (like continuous AF + lens "issues" + file size).

Colin

Wintereater wrote:

I turned off exp simulation, and it didn't fix it. However, I did discover something weird. So at max aperture (f/5.0 in my case), servo AF works as expected (7fps). Stopping down from 5.6-8.0 it slows way down (3-4fps), but from 9.0 and above, it quickens back up noticably (6 fps), although not to max speed. I'm so confused. I have every setting set to manual so I don't know what could possibly be changing.

Did you actually observe your aperture as I recommended? It’ll be an eye-opener. At many exposure combinations the lens will remain stopped down or partially stopped down (in Servo AF mode). The ISO and E/V of the scene will also affect this. If you watch, you’ll see that the aperture will remain (wide) open at other times.

I’d presume that this behavior is to facilitate AF (and maybe other functions?)

Edit: after turning off my camera and on again, anything below max aperture resulted in the same, below max speed burst rate, but it was consistent at all apertures for some reason. I even turned off auto white balance but no change.

Maybe try resetting your camera back to Factory Default (always a good starting point).

Also, if the exposure sim. and aperture thing were true, then the slowdown when using one-shot af shouldn't be happening.

True.  As to why your framerate is slowed in One Shot AF mode, perhaps the lens is partly to blame. Check lens firmware?

I don’t recall a slowed framerate when I had my M5.  I always had all in-camera processing disabled though.  Check all of your settings.

Since you mention that your Canon lens exhibits largely the same issue, it has to be something common to both (as you’ve been speculating).  Have you tested this in different environments?  You aren’t using flash by chance?  (The M5’s responsiveness is slowed greatly).

Well, good luck to you.  Be sure to report back!

R2

Bear in mind that generally higher ISO shots have larger file sizes, which may influence burst rate. So, stopping down will increase ISO (either on Auto or manually, assuming you adjusted the exposure to suit the slower aperture), which will generally increase file size.

I controlled for ISO by keeping it low during my tests and still had slowdown immediately after shutting down, irregardless of what the exposure was like in the end. I even changed the JPEG size to the smallest possible to eliminate any issue with file size

I cannot explain why it would speed back up at f9 though ?

After testing more, the slowdown at each aperture varies for some reason. The one thing that remains consistent though is that it slows down from max any time I stop down (even half a stop), and it never slows at max aperture (which isn't very bright to begin with with my lenses).

Do you have continuous AF (different to servo AF) turned on ? That may be trying to focus between shots even if on One Shot ?

There are only autofocus modes on the M5, One-shot and Servo AF. One shot should not be focusing between shots in burst mode and yet it slows, though not as dramatically (only losing maybe 1-2fps).

It could be a 3rd party lens peculiarity ? Since your 15-45mm behaves differently, it may be a combination of things (like continuous AF + lens "issues" + file size).

Colin

I don't think it's a third party lens issue. While it does behave slightly differently with canon's own lens, it still happens :/

Thanks for your input.

Did you actually observe your aperture as I recommended? It’ll be an eye-opener. At many exposure combinations the lens will remain stopped down or partially stopped down (in Servo AF mode). The ISO and E/V of the scene will also affect this. If you watch, you’ll see that the aperture will remain (wide) open at other times.

I’d presume that this behavior is to facilitate AF (and maybe other functions?)

I did check, and it behaves like I though it would (opening up all the way between shots during burst mode). I even set the aperture to the smallest it can go. I tested it in bright environments and dark environments and the behavior is mostly the same.

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

True. As to why your framerate is slowed in One Shot AF mode, perhaps the lens is partly to blame. Check lens firmware?

Everything is up to date.

I don’t recall a slowed framerate when I had my M5. I always had all in-camera processing disabled though. Check all of your settings.

I might try that. Even things like chromatic aberration correction and periphery illumination correct?

Since you mention that your Canon lens exhibits largely the same issue, it has to be something common to both (as you’ve been speculating). Have you tested this in different environments? You aren’t using flash by chance? (The M5’s responsiveness is slowed greatly).

I tested it in both light and dark environments, and the amount that it slows down seems unrelated to the light levels and ISO. No flash.

Thanks for your input.

Wintereater wrote:

Did you actually observe your aperture as I recommended? It’ll be an eye-opener. At many exposure combinations the lens will remain stopped down or partially stopped down (in Servo AF mode). The ISO and E/V of the scene will also affect this. If you watch, you’ll see that the aperture will remain (wide) open at other times.

I’d presume that this behavior is to facilitate AF (and maybe other functions?)

I did check, and it behaves like I though it would (opening up all the way between shots during burst mode). I even set the aperture to the smallest it can go. I tested it in bright environments and dark environments and the behavior is mostly the same.

Then you're missing it. It does stop down at certain exposure settings in servo mode (I've witnessed it). Once it reaches a low enough E/V, it'll open the aperture back up in order to facilitate AF.

However I don't think that's the cause of your delay issue. The slowdown that you're describing is too consistent. I have witnessed a slowdown when flash is used, and narrowed it down to new flash communication protocols (as it gets distance information from the lens).  That can be overcome tho.

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

Maybe someone else will chip in.  I sold my M5 when I picked up the M6ii (no slowdowns at 3, 7, 14, or 30 FPS.).

True. As to why your framerate is slowed in One Shot AF mode, perhaps the lens is partly to blame. Check lens firmware?

Everything is up to date.

I don’t recall a slowed framerate when I had my M5. I always had all in-camera processing disabled though. Check all of your settings.

I might try that. Even things like chromatic aberration correction and periphery illumination correct?

Still, those are normally performed after capture and shouldn't slow the framerate.

Since you mention that your Canon lens exhibits largely the same issue, it has to be something common to both (as you’ve been speculating). Have you tested this in different environments? You aren’t using flash by chance? (The M5’s responsiveness is slowed greatly).

I tested it in both light and dark environments, and the amount that it slows down seems unrelated to the light levels and ISO. No flash.

Dang.  We've covered about all the bases.  Running out of ideas.

R2

Wintereater wrote:

Did you actually observe your aperture as I recommended? It’ll be an eye-opener. At many exposure combinations the lens will remain stopped down or partially stopped down (in Servo AF mode). The ISO and E/V of the scene will also affect this. If you watch, you’ll see that the aperture will remain (wide) open at other times.

I’d presume that this behavior is to facilitate AF (and maybe other functions?)

I did check, and it behaves like I though it would (opening up all the way between shots during burst mode). I even set the aperture to the smallest it can go. I tested it in bright environments and dark environments and the behavior is mostly the same.

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

I still have my M6, as well as M6II, so I just tested the M6. Here's what I found. With EF-M mount lenses (I tested the EF-M 18-55 and the Sigma EF-M 16 F1.4) I notice no slowdown from 7fps when stopping down. However, when I use EF lenses with the adapter (I tested the EF 50 F1.8STM and the EF 85 F1.8), I do notice a significant slowdown when stopping down, even a little. I would say that it slows from 7fps to around 4fps. It's certainly a big enough difference that you can hear it right away. So, from this quick test at least, with the M6 it seems to be an adapter issue (I'm using Canon adapters).

True. As to why your framerate is slowed in One Shot AF mode, perhaps the lens is partly to blame. Check lens firmware?

Everything is up to date.

I don’t recall a slowed framerate when I had my M5. I always had all in-camera processing disabled though. Check all of your settings.

I might try that. Even things like chromatic aberration correction and periphery illumination correct?

Since you mention that your Canon lens exhibits largely the same issue, it has to be something common to both (as you’ve been speculating). Have you tested this in different environments? You aren’t using flash by chance? (The M5’s responsiveness is slowed greatly).

I tested it in both light and dark environments, and the amount that it slows down seems unrelated to the light levels and ISO. No flash.

Thanks for your input.

Wintereater wrote:

Bear in mind that generally higher ISO shots have larger file sizes, which may influence burst rate. So, stopping down will increase ISO (either on Auto or manually, assuming you adjusted the exposure to suit the slower aperture), which will generally increase file size.

I controlled for ISO by keeping it low during my tests and still had slowdown immediately after shutting down, irregardless of what the exposure was like in the end. I even changed the JPEG size to the smallest possible to eliminate any issue with file size

I cannot explain why it would speed back up at f9 though ?

After testing more, the slowdown at each aperture varies for some reason. The one thing that remains consistent though is that it slows down from max any time I stop down (even half a stop), and it never slows at max aperture (which isn't very bright to begin with with my lenses).

Do you have continuous AF (different to servo AF) turned on ? That may be trying to focus between shots even if on One Shot ?

There are only autofocus modes on the M5, One-shot and Servo AF. One shot should not be focusing between shots in burst mode and yet it slows, though not as dramatically (only losing maybe 1-2fps).

Continuous AF is a menu setting, not a AF setting. It is where the camera will try to AF even if the button is not pressed (eg. the camera will try to AF when it is lying on a table turned on with no-one touching it). I don't know whether this would have any affect, but it is worth trying.

It could be a 3rd party lens peculiarity ? Since your 15-45mm behaves differently, it may be a combination of things (like continuous AF + lens "issues" + file size).

Colin

I don't think it's a third party lens issue. While it does behave slightly differently with canon's own lens, it still happens :/

Thanks for your input.

I still have my M6, as well as M6II, so I just tested the M6. Here's what I found. With EF-M mount lenses (I tested the EF-M 18-55 and the Sigma EF-M 16 F1.4) I notice no slowdown from 7fps when stopping down. However, when I use EF lenses with the adapter (I tested the EF 50 F1.8STM and the EF 85 F1.8), I do notice a significant slowdown when stopping down, even a little. I would say that it slows from 7fps to around 4fps. It's certainly a big enough difference that you can hear it right away. So, from this quick test at least, with the M6 it seems to be an adapter issue (I'm using Canon adapters).

Sweet, thanks for testing it out! The M5 and M6 have pretty much the same specs so I'm surprised that you had no issues with your native EF-M glass but I did. Someone else commented about their M6 Mark II having no slowdown whatsoever so it could possibly be processor related (correlated or causation?) or some other spec.

You didn't mention it but I assume you had no slowdown on your Mark II, right?

Continuous AF is a menu setting, not a AF setting. It is where the camera will try to AF even if the button is not pressed (eg. the camera will try to AF when it is lying on a table turned on with no-one touching it). I don't know whether this would have any affect, but it is worth trying.

Oh my mistake. I always have that turned off since it messes with my slow-focusing lenses.

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

Maybe someone else will chip in. I sold my M5 when I picked up the M6ii (no slowdowns at 3, 7, 14, or 30 FPS.).

The main reason I posted this question was to find out if the newer canon mirrorless cameras had this issue, so thank you for your input (although the M6 Mark II doesn't really interest me. Still hoping for an M5 Mark II). Have you tested out AF-Servo burst shooting with non native lenses? (EF, EF-S, third party) at all? Another user reported this issue, but only with non EF-M glass.

Wintereater wrote:

I still have my M6, as well as M6II, so I just tested the M6. Here's what I found. With EF-M mount lenses (I tested the EF-M 18-55 and the Sigma EF-M 16 F1.4) I notice no slowdown from 7fps when stopping down. However, when I use EF lenses with the adapter (I tested the EF 50 F1.8STM and the EF 85 F1.8), I do notice a significant slowdown when stopping down, even a little. I would say that it slows from 7fps to around 4fps. It's certainly a big enough difference that you can hear it right away. So, from this quick test at least, with the M6 it seems to be an adapter issue (I'm using Canon adapters).

Sweet, thanks for testing it out! The M5 and M6 have pretty much the same specs so I'm surprised that you had no issues with your native EF-M glass but I did. Someone else commented about their M6 Mark II having no slowdown whatsoever so it could possibly be processor related (correlated or causation?) or some other spec.

You didn't mention it but I assume you had no slowdown on your Mark II, right?

Yes, I tested the M6II with the EF-M 32 and the adapted 85. No slowdown.

Alastair Norcross wrote:

Wintereater wrote:

I still have my M6, as well as M6II, so I just tested the M6. Here's what I found. With EF-M mount lenses (I tested the EF-M 18-55 and the Sigma EF-M 16 F1.4) I notice no slowdown from 7fps when stopping down. However, when I use EF lenses with the adapter (I tested the EF 50 F1.8STM and the EF 85 F1.8), I do notice a significant slowdown when stopping down, even a little. I would say that it slows from 7fps to around 4fps. It's certainly a big enough difference that you can hear it right away. So, from this quick test at least, with the M6 it seems to be an adapter issue (I'm using Canon adapters).

Sweet, thanks for testing it out! The M5 and M6 have pretty much the same specs so I'm surprised that you had no issues with your native EF-M glass but I did. Someone else commented about their M6 Mark II having no slowdown whatsoever so it could possibly be processor related (correlated or causation?) or some other spec.

You didn't mention it but I assume you had no slowdown on your Mark II, right?

Yes, I tested the M6II with the EF-M 32 and the adapted 85. No slowdown.

Great to know! thank you!

Alastair Norcross wrote:

I still have my M6, as well as M6II, so I just tested the M6. Here's what I found. With EF-M mount lenses (I tested the EF-M 18-55 and the Sigma EF-M 16 F1.4) I notice no slowdown from 7fps when stopping down. However, when I use EF lenses with the adapter (I tested the EF 50 F1.8STM and the EF 85 F1.8), I do notice a significant slowdown when stopping down, even a little. I would say that it slows from 7fps to around 4fps. It's certainly a big enough difference that you can hear it right away. So, from this quick test at least, with the M6 it seems to be an adapter issue (I'm using Canon adapters).

Wow, thanks for testing Alastair!

I think the reason it doesn't ring a bell is that whenever I was shooting bursts, I was almost invariably at max aperture.  Tells me something about my shooting habits!

R2

Wintereater wrote:

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

Maybe someone else will chip in. I sold my M5 when I picked up the M6ii (no slowdowns at 3, 7, 14, or 30 FPS.).

The main reason I posted this question was to find out if the newer canon mirrorless cameras had this issue, so thank you for your input (although the M6 Mark II doesn't really interest me. Still hoping for an M5 Mark II). Have you tested out AF-Servo burst shooting with non native lenses? (EF, EF-S, third party) at all? Another user reported this issue, but only with non EF-M glass.

Hold the phones!

I just put my (adapted) 100L on the M6ii, and it did slow substantially when stopped down while in 15 FPS mode (but curiously enough not while in 7 FPS mode).

No slowdown at all when I have any EF-M lenses mounted (Canon or Sigma).  I haven't tested them All though.

R2

R2D2 wrote:

Wintereater wrote:

Maybe try resetting your camera back to Factory Default (always a good starting point).

I haven't tried resetting. I was hoping that someone with similar canon cameras would test theirs out to see if the same thing happens lol.

Maybe someone else will chip in. I sold my M5 when I picked up the M6ii (no slowdowns at 3, 7, 14, or 30 FPS.).

The main reason I posted this question was to find out if the newer canon mirrorless cameras had this issue, so thank you for your input (although the M6 Mark II doesn't really interest me. Still hoping for an M5 Mark II). Have you tested out AF-Servo burst shooting with non native lenses? (EF, EF-S, third party) at all? Another user reported this issue, but only with non EF-M glass.

Hold the phones!

I just put my (adapted) 100L on the M6ii, and it did slow substantially when stopped down while in 15 FPS mode (but curiously enough not while in 7 FPS mode).

No slowdown at all when I have any EF-M lenses mounted (Canon or Sigma). I haven't tested them All though.

R2

Right, so I just tested my adapted 100L on the M6II. At F2.8 in 14fps mode it gives exactly 14fps (within 0.1 either side). When I stopped it down to F4, it slowed to 11.3fps. Not a huge slowdown (and still faster than my previous speed demon, the 7DII), but definitely there. I tested it by shooting my iPhone in stopwatch mode, so I could see exactly how many frames it shot in the time. When I tested my Sigma 16 F1.4 at F2.8, I got 14fps, so no slowdown there. What did your M6II slowdown to with the 100L? And what did you stop it down to? Pretty much the only lens I use at 14fps with my M6II is the Canon 70-200 F2.8L IS II, and, like you, I'm always shooting that wide open (that's the point of that lens), so I'm not going to notice a slowdown.