Coming back from family vacation from Mallorca where I used my 2 months old Sony A7IV (ILCE-7M4) and also tested the effect of using silent or mechanical shutter on the photos' dynamic range I wondered how much I used the mechanical shutter (called as 'shutter count') of my camera. I knew I had less than 2000 clicks (mainly with silent shutter) before left, and returned with cca. 3000 photos (mostly taken with mechanical shutter), so my total clicks should not exceed 5000.
As known, the 'shutter count' is the number of the mechanical shutter (Focal-plane shutter) actuation of a camera, however, in case of a mirrorless model one may take tens of thousands of photos with the electronic shutter, and the 'shutter count' still remains zero, if has not used the mechanical shutter, at all. Opposed to the electronic shutter the mechanical shutter has an expected lifespan, and the higher the actuation number ('shutter count') the more the camera lose its market value, so it's wise to keep an eye on this number.
There are couple of websites provide free service to show the camera 'shutter count' value by reading it from an uploaded camera JPG or RAW file (How to Check Your Camera’s Shutter Actuation Count). I submitted a fresh RAW file to https://shuttertool.com/, (as recommended by PetaPixel), also to https://www.camerashuttercount.com/, and both showed my 'shutter count' with the value of 9665! Uhm, surely know I have no more than 5000 clicks in that new camera, so how is it possible?
I started to verify my camera config settings to understand what could have caused this unreal high number. I took a few test photos with various shutter settings and uploaded the image files to 3 different free 'shutter count' provider websites and observed the followings:
use of fully electronic shutter – as expected, it does not increase the 'shutter count'
using mechanical shutter with EFCS (Electronic Front Curtain Shutter) ON, (here only the [mechanical] rear curtain moves) – the 'shutter count' increases with 1, as expected
use of mechanical shutter with EFCS OFF, (when both the front and the rear curtains move) – the 'shutter count' increases with 2, NOT as expected! Note: regarding the shutter curtains roles, see explanation later.
Wondered, whether the double counting is a camera settings issue, I did reset my camera to factory defaults and repeated the tests. I got the same results :(
Ok, so then it might be a firmware issue! I updated my camera firmware version from 1.11 to 2.00 (latest). Repeated the mentioned tests again, and got the very same findings, again!
Well, understanding the possible negative side effects of using EFCS (ON) on image quality (ref. What Is the e-Front Curtain Shutter function? vs Mechanical vs Electronic Shutter vs EFCS) I always set EFCS OFF when use the mechanical shutter. One may argue if it makes sense or not, my personal choice is using fully mechanical or fully electronic shutter, no hybrid mode (when EFCS is ON) preferred.
In order to make clear the term 'mechanical shutter actuation' first need to understand what exactly is the mechanical shutter. See excerpts of the definition by two different sources:
"In a modern DSLR or mirrorless camera, the mechanical shutter has two curtains or blinds, each made of several blades, that open to let light reach the sensor and then close at the end of the specified exposure time. It uses two curtains so that the exposure is consistent across the whole sensor" (Ref. What Is the e-Front Curtain Shutter function?)
"In general, focal plane shutters use two mechanical shutter curtains. The front and the rear curtain shutter which are located in front of the image sensor.
In mirrorless and translucent mirror cameras, the shutter stays open during live-view mode before you take a picture. The front curtain closes when the shutter button is pressed, and then opens again to expose the image sensor to light for a given exposure time (shutter speed). The rear curtain closes after the given exposure time is done." (Ref. What Is the e-Front Curtain Shutter function?)
Recommend also, to check out an excellent visual demonstration on YouTube How Shutter Works (from 1.15 m).
Confirmed then, a (conventionally used) mechanical shutter unit consists of 2 (the front and the rear) curtains, which are positioned on the opposite side of the shutter unit (at the top and bottom) and one standard actuation (or cycle) consists of the activation of both curtains. As mentioned, with EFCS ON the [mechanical] front curtain is not used, instead, the exposure starts electronically, but it is finished by the [mechanical] rear curtain.
For geeks only: What is the difference in the mechanical shutter operation in DSLR and mirrorless cameras:
in a DSLR before picture taking the front curtain is closed. Pushing the shutter button triggers the front curtain to open, followed by the rear curtain close, then front curtain close and rear curtain open. The front curtain remains closed after the click.
in mirrorless cameras the curtains (they both together are the parts of the MECHANICAL SHUTTER, just like in DSLR) run the same amount of movement in an actuation cycle, but the front curtain moves in reverse order. Initially, both curtains are open. A 'click' triggers the front curtain to close and to open immediately, followed by the close and open cycles of the rear curtain. Both curtains stay open after a photo is taken.
As we now from a DSLR World one click (in single shooting mode) results one photo and an increase with 1 in the 'shutter count'. As also understood, the shutter in mirrorless cameras built and work technically by the same way as in DSLR: under one actuation cycle the two opposite-located curtains have an open and close motion (in different order), so 1 click should increase the 'shutter count' value with 1, as well.
Anyway, even if all the above terms are clear and valid SONY might apply a different logic how 'shutter count' is measured, so let's check another SONY camera. NOT to my surprise I found the 'shutter count' increases with 1 even if I use the mechanical shutter having EFCS ON or OFF in my A7III. Actually, it really makes sense, as 1 click is just one actuation of the shutter mechanism, as we just discussed, and does not matter if only the rear or both curtains used. Seems the teams at SONY worked on the A7III and A7IV firmware did not talk to each other? Are not there internal standards how to handle attributes like 'shutter count'?
So far I had a couple of mirrorless cameras (mostly Fujifilm models, like the X-T3, S10, T20, etc), where I also used the EFCS OFF (so both mechanical curtains activated), and never saw double counting for a single click. Just double checked a series of consecutive RAW files from these Fujis at page How many shots has my Fuji taken? and reconfirmed the 'shutter count' always increased with 1 when the mechanical shutter was used.
By the way, why is it an issue to double count the mechanical shutter use for a camera? Well, this works the same way as the milage in cars. The more shutter count your camera (or the more milage your car) has the less money you may get when sell it on the second hand market. Now, imagine, you use your A7IV camera for 2-3 years and took 50k photos all with the mechanical shutter with EFCS OFF, and your 'shutter count' is showing 100k actuation cycles! The camera is less attractive for potential buyers and finally you can sell your camera at a considerably lower price with this high level of apparent use! (ref. Sony Shutter Count Guide: Everything You Need to Know About Shutter Count and Your Sony).
Suspecting a generic firmware issue with the Sony A7IV cameras I contacted SONY.HU support and described the ILCE-7M4 shutter count miscalculated issue, also asked to forward my findings to the global software development team.
SONY.HU first advised to leave the camera at an official service point for inspection. I did, and the Service engineer confirmed the higher value of shutter count, also stated the same what SONY.HU replied later via e-mail. See translation of the message in English:
"The camera counts the clicks of the shutter, and not the number of the photos the camera took. In case the EFCS is OFF then both the shutter curtains move, so the shutter count increases with 2, while with EFCS ON the camera counts 1 for every actuation. However, when using fully the electronic shutter the shutter count of the camera won't increase."
Well, these statements agrees with my findings and seems SONY is aware of this behavior of the given model. Anyways, based on the above explanation I still believe counting 2 for 1 actuation of the shutter mechanism is incorrect, and not only incorrect, but also not consequent for various Sony alpha models, (see the example of A7III), where the shutter count works correctly, as expected. Unfortunately, I have no information about other SONY models how the count works there.
And now, do you want an even faster pace of growth of your A7IV shutter count? Here is the way.
As known, SONY implemented a well-anticipated anti-dust protection for lens exchange: one can set the shutter to close when power off the camera, physically separating the sensor from the outer air. For now I bet you already have an assumption: yes, both the curtains close when power off the camera, then open, when power on. Yes, this is one more cycle per curtain, so increase the 'shutter count' by 2.
When use fully manual shutter and power off the camera after each shot your 'shutter count' increases with a whopping value of 4 (2 by the exposure driven by both mechanical curtains, then additional 2 by closing, then opening both curtains by power off and on, respectively).
When activate EFCS (ON), then 'shutter count' increases with 3 per each click and power off (1 per the rear curtain when taking the photo, then plus 2 by closing then opening both curtains for power off and on.
Fully aware, these uses are not real life examples, but support well my theory on the weird A7IV shutter count calculations, also still good to know these things, and help to use functions, when they are really needed (use the electronic shutter whenever possible and activate the referred anti-dust function only for lens exchange in dusty, windy conditions).
Unnecessary to say having 'shutter count' value 5k or 9-10k in a camera does not make a real difference, since the camera is still at the beginning of its life-cycle, but, with the experience recently gained it is easy to prevent the high pace 'shutter count' growth and the the excessive value loss of the unit in longer term.
Believe, my two tests together undoubtedly prove that SONY counts the curtain activation separately instead of considering the shutter (incl. the 2 curtains) as a working unit in terms of 'shutter count'. Seems, the same bug or misconception cause further "apparent lifetime" shortage of the A7IV body.
Now I understand why my '5000 click camera' has over 9000 'shutter count' value:
I deactivated EFCS, so every click increased the value with 2
As mostly photographed at the sandy beach I activated the "shutter close at power off" feature. In order to save battery I tend to switch off the camera very often (when not using), which increase the shutter-use-value by 4 with these many before-camera-shut-down photos.
Taking 3 to 3.5k photos with these settings easily doubles the number of the real clicks (~5k) and turned into a false high 'shutter count' value.
Need to mention the 'shutter count' value read from the camera RAW or JPG files by a 3rd party web application might differ from the value read directly from the camera by official SONY support, but think it is quite unlikely, as the mentioned sites explicitly mention the supported camera brands and models, also, never heard a related complain.
Wonder what is your experience with various brands and various models regarding the calculation of the 'shutter count'?
Do you also believe SONY should release a firmware update to fix the counting issue for the affected model?
Sony cameras are high value and high value retaining products in general, and I am happy to use the E-mount platform for the excellent quality and very handy cameras, and also for the wide lens choice the platform offers. The above described software (firmware) issue obviously does not affect the functionality of the mentioned camera model, but negatively affects to retain its value over the years. That's why I expect SONY to revise the revealed issue and release a firmware update which fixes the 'shutter count' determination.