Canon EOS M6 Mark II - Analysis of Shutter Shock

During some discussions, shutter shock came up with the Canon EOS M6 Mark II.  Simply put, shutter shock is the vibration that happens at the start of the exposure caused by the movement of the shutter.  This usually happens in slower shutter speeds around 1/200th to 1/25th shutter speed.

Usually, this isn’t a problem on Canon mirrorless, because they used to always have EFCS (Electronic First Curtain Shutter).  In basic terms, there is the first curtain (the shutter opens up) and the rear curtain (the shutter closes) to control the exposure.  To minimize shutter shock, manufacturers employ EFCS so that the first curtain is done electronically and not mechanically.  This eliminates shutter shock.

Electronic shutter is something different – this is when the camera electronically controls the start of the exposure and the completion of exposure electronically.  This is also called silent shutter because there is no noise whatsoever when the camera takes a picture.

However, there are problems with a fully electronic shutter and that has to do with the readout speed of the sensor.  The slower the sensor and the more “rolling shutter” the sensor will exhibit with motion, and banding with some forms of lighting.  So it’s not a perfect replacement for EFCS.

For some unexplainable reason, with the M6 Mark II, there is no EFCS.  There is an electronic shutter, but no EFCS.

While during usage, I’ve never experienced shutter shock with this camera, or so I thought.

Since we have the ability right now to test lenses, and measure the results, testing the effect of shutter shock with a variety of EF-M lenses is possible.

Since the M6 Mark II has a fully electronic shutter – testing the M6 Mark II in mechanical shutter versus electronic should tell us if we are indeed missing out on having EFCS.  (again, both a fully electronic shutter and EFCS, share the first curtain being electronic).

The test scenario consists of

• A high resolution MTF edge diagram
• M6 Mark II on a tripod in the portrait position.  This was chosen so that the shutter movement was not against the strongest part of the tripod.  With the camera on its side in portrait position, the shutter movement is “pushing” to the side of the tripod, versus “down” as it would in the landscape position.
• The camera settings are Auto ISO and either Manual or Tv mode.  Shutter timer of 10 seconds is used to effectively dampen any shot to shot vibrations with the mechanical shutter.
• The camera is not touched for shooting.  Shooting the image and changing the shutter speed is done via Wifi. The camera is only touched when changing the shutter from mechanical to electronic which is at the start of the sequence.
• The sequence starts at 1/400th of a second and goes to 1/10th of a second in 1/3 stop increments.
• The MTF 50 is measured and compared between electronic shutter and mechanical shutter.
• IS was turned off the lenses (prior to these tests I compared the results with and without IS and it made very little difference)
• We are using out of camera JPEG with sharpening set to default, and all corrections turned off.  We aren’t really concerned about the MTF values, simply the difference between the values achieved by the two shutter methods.

The first lens was one in which I thought would show the poorest performance for shutter shock.  Atypically longer lenses show it the worst.  The EF-M 55-200mm was the first lens I tested at 200mm.
Here are the results at 200mm.

Yeah. Umm. Wow.

Being this dramatically different was completely unexpected. I should note, that I repeated this test three times to compare the results to see if it was measurement error and each test returned very similar results.

For 1/400 to 1/250 you will notice that the absolute lp/mm delivered by both the mechanical and electronic shutter is lower – this is because it was higher ISO.  Interestingly, this is also a means of testing high ISO capability of a camera – I wonder how come no one is doing it this way? 

From the result we can see that from 1/200 down to 1/80 in full mechanical mode, the image quality is far less than electronic, with 1/80 being the worst.  However, the mechanical shutter never does significantly improve until it starts to get better by around 1/10th of a second, but still trails dramatically.  Both the mechanical and electronic test images used the same ISO for the same shutter speed, so there’s no variance in caused by ISO’s (as an example, if the 1/125th image for mechanical shutter used a higher ISO than the 1/125th image for the electronic shutter – in this case, both images for 1/125th were ISO 1000).

It is fair to say that at 200mm, do NOT use the mechanical shutter if you can help it.

We also tested at 55mm to see if the 55-200mm lens fared better when you decreased the focal length.

As you can see the results are much better, there are minimal differences between the mechanical and electronic images.  You probably in the real world would not even notice the difference between these two.  The worst value seems to be around 1/100 to 1/60th of a second.

The conclusion we can make from the EF-M 55-200mm is that care must be exercised as you increase the focal length.  As you get closer to 200mm the mechanical shutter will dramatically reduce the image quality.

Canon EF-M 15-45mm

The next lens we took a look at was the EF-M 15-45mm, expecting good results because at 55mm the EF-M 55-200mm was pretty good.
 
I was a little surprised by these results because they were a lot poorer than the EF-M 55-200mm.  It appears as if the EF-M 15-45mm is it's worst, well from around 1/160th of a second through 1/20th of a second.  Perhaps the IS unit isn't as rigid as more expensive lenses, and there's a little bit of optical element movement even with IS turned off? I think more testing is necessary for this lens.

This is a lens that looks like it takes a hit with the camera not having EFCS.  If you can and if you need the most exacting resolution from the EF-M 15-45mm then I suggest you use an electronic shutter when you can.

Canon EF-M 32mm F1.4

The next lens I wanted to test, was a prime that didn’t have IS – just to see if the non IS lenses fared better.  So I tested one of my personal favorites, the EF-M 32mm F1.4.

 
We can quickly see that shutter shock does not seem to be a problem with non IS lenses. Or possibly none Zoom / IS lenses.  There are little differences between mechanical and electronic shutter when the EF-M 32mm is used.  Here you can really see the difference that ISO makes on the resolution.  I ran this test twice just to make sure I didn’t mess up and not switch the camera in between electronic and mechanical.  The test results were the same in both cases.

Conclusion

I’m disappointed in Canon.  The M6 Mark II is a hopped-up little camera that is fun to use and is an amazing performer – but the deliberate lack of EFCS on this camera reduces it’s ability in some cases to deliver the highest IQ possible. The M6 Mark II (as well as the 90D) are the two most exacting and demanding cameras on the market today, as both have 32.5MP APS-C sensors when the rest of the industry mostly has 24MP.  However, this makes it more puzzling as it is more prone to show the effects of shutter shock than any other camera as well.

This demanding sensor will show any camera warts – and this is a pretty ugly one, with a long hair stuck in the middle of it.

The problem may be the IS units in the EF-M lenses as they be slightly moving with the shutter vibration, but there is one thing for certain - using the mechanical shutter with at least the EF-M image-stabilized lenses we have tested so far - is a problem.

To be fair, in most cases, the M6 Mark II camera even without EFCS will have enough resolution that even if you do use the mechanical shutter – you won’t see the difference on your final print unless you are printing super huge, and if you are printing super huge then you are going to be most likely using a prime lens anyways.  It is not an excuse, because as far as I’m concerned there is no excuse for not having an EFCS option when that option has existed in every Canon camera since I believe the EOS 40D.  Yes, that long ago.

If you like having the potential of printing or viewing large, or cropping significantly then you should be aware of the possible limitations of the lack of EFCS on the M6 Mark II.  Shooting images with the mechanical shutter, you want the shutter to not fall within the range of 1/200 to 1/50 of a second, if you have an EF-M lens with IS (or one of the zooms apparently).   Shutter speeds in this range will have issues with shutter shock and will degrade your image quality.  If you must shoot within those shutter speeds, consider switching to the electronic shutter.  However, keep in mind that lights and motion will not appear correct using an electronic shutter.  This does not mean the entire camera is trash, it simply means that the camera has some very specific limitations to when you can use the mechanical shutter.  You have to be aware of those if you want the best possible image quality from your camera.

From doing these tests, we will be continuing to further rest the EF-M lens catalog in more detail against both mechanical and electronic shutters. 

Addendums

May 6th

Added some clarity to the conclusion.

May 5th 

Since many have asked about the performance with and without IS.  This was the sample test using the EF-M 55-200mm at 200mm with the test scenario described above.

The lp/mm may not be the same across charts, because this was a preliminary dataset taken just to prove the theory that testing for shutter shock this way would actually work well.  As you can see, the difference between IS and no IS in this case, is down to purely measurement differences.

May 7th

Further discussions about raised the point of why the EF-M 32mm F1.4 didn't exhibit the same problems and if you could technically define it as shutter shock then.

This did cause me to pause, and I had to think back to some hazy knowledge on Canon's "cheaper" IS units I recalled that someone mentioned they were working with springs to reduce size, weight and cost.  Finally found a reference in the digital picture which mentioned that the IS units in Canon's EF-S 10-18mm lens contained had a IS lock like "image stabilization optics are locked in place with a spring suspension mechanism rather than a center lock mechanism.".  This would lead the lens to be more susceptible to the shutter vibrations.  With the IS unit on, it could be that the gyros are getting the vibration from the shutter but unable to move the IS unit fast enough to correct for it.

A possible conclusion to all this is that shutter shock is the cause of the problem and it's amplified by the fact that EF-M lenses contain a weaker / lighter / cheaper IS units than Canon's, for instance, L grade lenses. 

This is why we are seeing the effect more on the EF-M IS lenses and less on the EF-M 32mm F1.4 (but do note, the effect is still there, just much much less and nothing to worry about).  This probably also means that if you are attaching a EF L lens to the camera, you may not have a problem, if you lock the IS in the off position.

Of course, this is all just guesswork, and there's only one company that actually knows the real answer for this.  If we ever get through COVID, I'll ask them ;)

We will still include in with our lens tests, a shutter shock test, because until Canon fixes this problem - it is information you should be aware of if you are shooting with the Canon M6 Mark II with any of Canon's EF-M lenses that contain image stabilization.

May 9th

Some have suggested that it may be the tripod resonance causing most of the issue, so today I took out the EF-M 15-45mm and shot it handheld.  With the mechanical shutter the Lp/mm at 45mm was 35.8 and with the electronic shutter the lp/mm was 42.7.  That is a 16% degrading at 1/200th of a second.  The values that were done on the tripod was 43.8 lp/mm with electronic shutter and 34.0 lp/mm with the mechanical shutter - basically within measurement/testing error.

I think it's safe to suggest, that the tripod is not adding undue vibrations into the test at this time.

Also I think important to note, was that my grip on the camera at the time of shooting was the traditional two-handed grip, with my left hand cupping around the bottom of the lens for support.