Why does a mirrorless camera have a mechanical shutter?


JackAllTog Plus
10 5.7k 58 United Kingdom
17 Oct 2019 10:37AM
I'm hoping someone can help me understand why does a mirrorless camera have a mechanical shutter? I can understand why some mirrorless cameras have a sensor cover when you change lenses. But what is the benefit of a physical shutter on a mirrorless camera?

E.g. spec's like this for the new OM-D E-M5 mk III
Continuous Shooting 30 / 10fps (electronic / mechanical) - https://www.ephotozine.com/article/olympus-om-d-e-m5-mark-iii--vs-olympus-om-d-e-m5-mark-ii-comparison---what-s-new--34122?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Ephotozine+%28ePHOTOzine%29

When would i choose mechanical over electronic, or does the camera choose for me?

Thanks
Stuart

Join ePHOTOzine for free and remove these adverts.

Chris_L 5 5.3k United Kingdom
17 Oct 2019 10:45AM
The sensor has XX million pixels and in order to create an exposure of 1/1000th second every pixel would have to be read in an incredibly short time. With a shutter you just expose the sensor to the light from that fraction of a second then process the information at your leisure like film but not quite.

Some people shoot electronic shutter all of the time but because of the way the sensor is read you can jet a jello effect and banding from led and fluorescent lighting.

You can opt to have electronic shutter for first curtain only and there's no real negative that I can think of when doing that.
JackAllTog Plus
10 5.7k 58 United Kingdom
17 Oct 2019 10:51AM
So if sensors could have global shutter reading - rather than sequentially reading the pixels then this would no longer be an issue.

Mechanical shutters create audible noise and that was one of the big benefits i wanted to see from mirrorless cameras.
Chris_L 5 5.3k United Kingdom
17 Oct 2019 2:38PM
Even with a global shutter a high res camera might not be able to get the speeds needed, having to switch the sensor on and on off so quickly, I believe that a real shutter can still have an advantage, and at high speeds a real shutter works as a curtain and it works well.

It surprised me when I got my first mirrorless. I expected it to work like a typical cameraphone or a compact.

In the kind of situations where you need silence you are probably going to be able to use electronic shutter without worrying about it. Slow moving stuff in silent churches, street photography of people at walking pace etc and in many high speed shutter situations - football, motorsports etc you can probably get away with the noise.
Paul Morgan 18 19.4k 6 England
18 Oct 2019 12:55AM

Quote:So if sensors could have global shutter reading - rather than sequentially reading the pixels then this would no longer be an issue.

Mechanical shutters create audible noise and that was one of the big benefits i wanted to see from mirrorless cameras.



The shutters are pretty quite in most of these things, some like silent shutter for the silence, some become self concious of the shutter noise as well thinking everyone can here it.

There not good for flash photography.
LenShepherd 11 4.0k United Kingdom
18 Oct 2019 8:51AM
One reason is to protect the delicate sensor surface when not actually taking pictures.

Another is that mechanical shutters have advantages when photographing subjects moving across the frame.

Sometimes the electronic shutter speeds available are less than for a mechanical shutter.

JJGEE 14 7.6k 18 England
18 Oct 2019 9:30AM

Quote:One reason is to protect the delicate sensor surface when not actually taking pictures.

Confused Sad

When I take the body cap or lens off of my camera I do not see a shutter only either the mirror or when flipped up the sensor area, which I believe is a filter not actually the sensor itself..... this is the thing I clean with a blower brush / wet swabs.
Chris_L 5 5.3k United Kingdom
18 Oct 2019 11:25AM

Quote:One reason is to protect the delicate sensor surface when not actually taking pictures

Definitely not a reason for the mechanical shutter. If the shutter was closed to protect the sensor there wouldn't be any image in the camera's viewfinder or on the LCD screen. When removing the lens, with the camera switched on or off I can see the sensor and clean it.
Tianshi_angie 4 2.6k England
18 Oct 2019 12:20PM
I see the sensor too - which I have cleaned but been unable to remove a spot on it!!!Sad
lemmy 12 2.8k United Kingdom
19 Oct 2019 6:33PM
With an electronic shutter when you press the shutter release the electronics start to read the first row of photo sites and scan through sequentially line by line reading and clearing them to the last . That takes time. If you set a speed of 1/1000th, each line is activated for that time in turn but that doesn't affect the time taken to run through the whole image scan, top to bottom.

With a mechanical shutter, the shutter closes when you press the release, then opens and closes for the shutter time set, the sensor is read and then cleared and the shutter opens again. So although the scan takes the same time, the photo sites have only been exposed for the length of time allowed by the shutter

Because the sensor scan time is slow, if you want to use flash you will be limited to a very slow shutter speed. Most cameras don't bother. Olympus allow you to use 1/20th. but that's of limited use except in the darkest of surroundings. For the same slow scan time reason, electronic shutters are not good with fast moving subjects due to subject movement during the scan. With my Panasonic G9, I can set a shutter speed of 1/32,000th but the scan readout remains the same.

The e-shutter has the advantage of allowing higher shutter speeds - 1/32000th as opposed to 1/8000th on my G9, for example and completely silent operation. It can't wear out and it saves battery power and it eliminates shutter shock. Plus, having no moving parts, it can operate at much higher frame rates for burst shooting.

The mechanical shutter, on the other hand, allows for much higher and therefore practical flash sync speeds and practically no distortion of fast moving subjects. Only two major advantages but both crucial. And that's why it is there.

There'll be a practical global shutter which can read each site at once some time in the future, I suppose but at the moment the amount of electronic circuitry necessary makes them a non-runner for consumer use.






Sign In

You must be a member to leave a comment.

ePHOTOzine, the web's friendliest photography community.

Join For Free

Upload photos, chat with photographers, win prizes and much more.