Electronic vs Mechanical Shutter for Diamond Ring and BBs

For those using mirrorless cameras to shoot the TSE, I have a question that I have been noodling. In previous eclipses, I have used mechanical shutter and have no issues pulling the solar filter off 15s before C2 and after C3 to capture the diamond ring and beads.

This year, I am planning to use electronic shutter on my Sony A7IV to keep any potential shutter shock and EQ mount vibration to a minimum.

At about 3am, my mind started asking if using electronic shutter during this phase exposes the sensor to more abuse. With a mechanical shutter, the sensor gets brief breaks from the harsh sun that it does not get with electronic (I think)

Any thoughts? Thanks in advance

I’m glad you asked this - I’ve been wondering the same, having just switched to mirrorless.

I was chatting with Michael Zeiler as part of our webinar prep last week and he mentioned that he and a bunch of hard core eclipse chasers were talking about this back in October at the annular eclipse and the general consensus was that removing filters up to a minute before C2 is ok, given the very high obscuration of the Sun.

Michael was shooting mirrorless then, so I guessing that was factored into the discussion - I may drop him a line and ask to confirm!

That said, as I understand it, mechanical shutters on DSLRS have two “curtains” (Front and back), some mirrorless still have a back curtain, and others (e.g. Nikon Z8, Z9) have neither, so it’s not entirely straightforward.


Thanks!! I have also spoken with another photog that shot electronic shutter at the 2019 eclipse with no issues. Sleeping peacefully now…

I’m not sure I understand the issue. With a mirrorless, the sensor is always exposed to whatever light is coming from the scene in between shots. The mechanical shutter only closes right before a shot is taken, and then again to terminate the exposure, after which it opens again. Many cameras also have a electronic first curtain option, in which the shutter doesn’t close at all, (except at the end) but the exposure is initiated electronically. Electronic shutter just takes this all the way and both initiates and terminates the exposure without the brief closure of the a mechanical shutter.

So since the shutter is open, and the sensor exposed, during all the time that a picture is not being taken anyway, I don’t see what difference the type of shutter actuation would make. The time that even a mechanical shutter is closed is very, very small compared to all the time the sensor is exposed.

For what its worth, I don’t have much concern about removing my filter, with the shutter open, at 30 seconds before C2. Even before mirrorless I used live view on dSLRs with the full sun in the frame without incident. Now, that would have typically been with a wide angle lens, and longer focal lengths do have more of a potential issue for damage. However, the little sliver of sun visible at 30 seconds just doesn’t transmit anywhere near as much total energy as the full disk. The other factor is time: if would take time for even full-sun energy to heat up a sensor to the point of damage; it would not be instantaneous. Since we are only exposing the sensor to the unfiltered light for a few seconds before C2 and after C3, there just isn’t much opportunity for accumulation of heat.

But am I missing some aspect of why the shutter actuation type would make a difference in mirrorless?


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That makes perfect sense! Duh! Of course the shutter is open the whole time anyway. Thanks for taking the time to straighten me out


With a mirrorless, the sensor is always exposed to whatever light is coming from the scene in between shots.

I guess I’m not 100% clear on what would be happening during any period when the camera was on but not showing any preview image, at least for mirrorless with a back curtain shutter. When “ready to shoot”, then, for sure it’s exposed.

Well, the only way that a mirrorless camera can display an image on the back screen or in the electronic viewfinder is from the sensor. So if you are looking at the scene through either of those, then the shutter must be open and the sensor exposed to light. If the camera has some way to be on but somehow have the mechanical shutter closed (and I can’t see what the utility of that would be), then the sensor would not be exposed, but of course you couldn’t see or compose the scene. My camera doesn’t have such a mode, put perhaps others do.

On my camera if I leave the physical on/off switch to On and just let it sit, it will display the scene seen by the sensor until a certain timeout is reached, at which point it turns of the display and probably most of the electrical functions of the camera, but the mechanical shutter remains open. Though the sensor may be deenergized, it is still exposed to light.

The mechanical shutter does close when I turn the physical switch to off, but even that is an option enabled by a menu function; without that enabled the shutter would remain open and the sensor visible even if I took off the lens.

So for instance during the eclipse the camera will be shooting continually with an interval timer, and the shutter will remain open and the sensor exposed the whole time. I don’t think I could set it up to be any different.


I’m sure you’re completely right - I need to learn more about the physical operation of mechanical shutters.

That said…

I can’t see what the utility of that would be

The utility could conceivably be precisely this scenario - optical protection for the sensor that is otherwise left exposed to whatever the uncovered lens happens to be pointed at, whether the camera is in use or not.

P.S. I did read through this but haven’t fully comprehended it yet:

Canon, at least, doesn’t seem to see the need for that, as there is no mechanism for that. However, when you switch the camera off, you do get a message admonishing you to keep the lens cap on when the camera is off, presumably to keep from exposing the sensor (or the shutter curtain, if you have chosen to enable that) from being burned by the sun, should you leave it pointing that way.

Paradoxically, and unlike my previous Canon dSLRS, the R5 does not automatically close the shutter when you take off the lens. I find this aggravating, as I used to routinely change lenses with the camera switched on without worrying about dust getting to the sensor. Now I have to remember to switch off the camera before changing lenses.


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