Disadvantages of electronic first curtain shutter?

Question

There is a setting in menu of my camera wether to use or not to use electronic first curtain shutter. So far I know that using electronic first curtain reduces shutter lag and the noise my camera makes when shooting photos. And electronic first curtain shutter could also be useful to reduce camera vibration when shooting distant subjects, like in moon photography.

So, three good reasons to use it. Should I use it? Is there any disadvantages when using electronic first curtain shutter? There must be, or why else would they even give me a setting in camera menu to choose whether to use it or not.

Answer 1

Summary:

• Usually useful. Noise reduction is significant.
  A single muted unsharp mechanical noise may be overlooked in many situations. But the "double tap" of two mechanical curtains is fairly distinctive.

• May cause problems with

  • high speed motion

  • older Minolta lenses
    The effect at high shutter speed is observed with 2 Minolta lenses that I tried, and not seen with 1 Sony lens. See end.

  • and at very high shutter speeds (~+ 1/8000 s)

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Added: See "Yes!!!" at end.
EFCS may cause large under-exposure at very high shutter speeds.
Sample of 1 so far. Mine !!!
Makes sense (see end) but exact basis as yet TBD.

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Sony SLT & mirrorless cameras and many Canon EOS DSLrs offer EFCS.

I have a Sony A77 SLT - I use it in EFCS mode and have only used mechanical FCS to compare the modes. For me the main advantage is reduced noise. The SLT fixed mirror and single shutter operation vastly reduce noise compared to a mirror plus 2 shutter actions SLR.

It is implied by Sony that the EFCS may cause image blurring with moving objectcsat large apertures at larger focal lengths. The rationale for this is given below - basically the EFCS has a finite dot writing speed which causes it to be unable to provide a high enough "enable" signal to start sensor light-writing.

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From this web discussion.

The Sony NEX5n manual says (lost in translation):

They note that Sony suggests EFCS not be used in some situations eg.

• When you shoot at high shutter speeds with a large diameter lens attached, the ghosting of a blurred area may occur, depending on the subject or shooting conditions. In such cases, set this item to [Off].

And then provides this plausible discussion:

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The first electronic curtain is likely rate limited by the clock it shared with readout. So it can't clear rows faster than it could read them. The second curtain isn't limited by this clock. A mechanical shutter with a sync speed of 1/250 exposing at 1/8000 will move a slit 250:8000 of the height of the frame across it. If the height has 4000 rows, then the size of this slit is 4000*250/8000 = 125 rows. For an electronic shutter, which has a sync speed of say 1/12 (at still resolution; the A77 shoots at up to 12fps, right?) this becomes 4000*12/8000 = 6 rows. At 1/24 it would be 12 rows. So if you're panning with a fast lens wide open, tracking a subject, it's not hard to see how the background could smear.

What they're really saying is that at high shutter speeds and narrow depth of field, turn it off when shooting moving subjects. Sports, wildlife; that sort of thing.

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Sony also say:

• When a Minolta/Konica Minolta lens is used, set this item to [Off]. If you set this item to [On], the correct exposure will not be set or the image brightness will be uneven.

See Stan's comment in this. I'd have thought that the camera could easily add delay if required - say a default delay if the lens is not in the camera's "library". And a user adjustable delay could easily be added.

And discussion says:

Not sure what the difference in lenses is; maybe newer Minolta and all Sony branded lenses have better defined aperture timing, or can go from one aperture to another without passing through an implicit reset state (wide open). Or some other practical difference that matters here.

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Yes!!!

My A77 often exposes incorrectly at very high shutter speeds - ay high ISO and bright day when subject matter swings from shadow into bright sun.
In aperture priority mode, as light increases shutter speed increases. As increaseing light moves shutter speed from 1/4000s to 1/6000s the image darkens appreciably and at 1/8000s the image is massively underexposed.

BUT I just tried this with mechanical front curtain shutter and the problem appears to vanish. This testing was done with CFL bulbs and a white ceiling as its 1am here but I'll be trying this in daylight asap.

In this case it may be that the very fine tolerances between electronic turn on and mechanical exposure removal are easily swamped by small error in mechanical timing.
Even at a full curtain traverse time of say 1/250s, to get 1/8000s effective the shutter needs to be open 250/8000 = 1/32 ~+ 3% of the width of the sensor. If shutter edge is "out" by 1% in position the exposure may be reduced by 1/3. A 2% position error gives only 1/3 exposure and a ~= 3% position error gives ~= darkness.

This may well be a calibration adjustment. More anon when/if I find out.

Added 2:

I do not have time now to experiment further at present but:

Exposure with and without EFCS at 1/8000s was good with Sony 50mm, f/1.8 (DT 1.8/50 SAM) even when imaging a CFL light bulb and surroundings at f/2.4.

Exposure problems occurred at 1/8000s with EFCS but NOT with mechanical FCS with

• Minolta 17-37 f/2.8-4 D -> usually an excellent performer.

• Tamron 28-200mm, f/3.8-5.6 -> an "only OK" lens overall.

Answer 2

The main disadvantage is that it won't work properly with all lenses (particularly A-mount or other adapted lenses, but also aging E-mount lenses). The mechanical delay introduced by the normal operation of the shutter will allow the iris to close down normally for just about any lens that isn't damaged (or suffering from major dust/grit ingestion); the timing is similar to the mirror flip of a traditional SLR. The EFCS (electronic front curtain shutter) reduces shutter lag to the point that the iris may not have time to close down completely, which can both affect overall exposure for long exposures and cause exposure grading (changes in exposure across the frame) for shorter exposures.

As long as you are using Sony E-mount lenses that are in good condition (or adapted lenses that are manually stopped down), it shouldn't be a problem.

Answer 3

I shoot with the Sony A77 and use the electronic first curtain shutter by default.

Pros:

• reduced audible noise(only second curtain makes sound)
• reduced lag between trigger and shutter actuations
• less physical inertia from the shutter and resulting in less camera shake

Cons:

• some have experienced exposure issues due to timing differences between the shutter and other components(lens aperture speed of stopping down, remote flash, etc.)
• uneven wear of the first vs second shutter
• potentially more sensor noise

I've personally not experienced the exposure issues, but that's just with my gear, setup, and use cases. Given sufficient illumination for proper exposure, the added heat/energy from the electronic noise shouldn't be an issue.

I have noticed that using the mechanical first curtain, I do experience more camera shake from the added inertia. The sound level difference is noticeable as well between the two modes.

Answer 4

To achieve even exposure, that first curtain may not turn on the whole sensor at once, but must travel at the same speed with mechanical second curtain. With current technologies, electronic curtain is slower than a mechanical one (which is why they haven't ubiquitously replaced mechanical ones after all), so the mechanical curtain has to be slowed down - resulting in less audible noise and shake. Disadvantages of the slower shutter: slower max sync speed and more pronounced rolling shutter. The more complex setup of synchronizing between first and and second curtain means higher chance of erratic exposure at highest speeds due to curtains misalignment.

With fully mechanical shutter, that electronic first curtain still has to be run through to turn on the sensor, and mechanical first curtain has to wait for that to finish before exposing the sensor. With electronic first curtain, there's no need for such wait, so there's less shutter lag - considered generally an advantage, but could feel like a small nuisance if you're already accustomed to a longer lag and are getting action shots earlier than expected. Such inconvenience should pass in matter of hours or days, but might matter when considering only brief usage. It has been speculated that some lenses might not have enough time to fully adjust aperture. This problem, if real, should be limited to very few digital era lenses though, since there was no need for such wait on film cameras either.

Answer 5

I know this post is old, but I wanted to put in my two cents.

I have a Sony A77 Mk2. The way I shoot is take multiple photos, then compare them at 100% magnification and look for any sort of blurring. I do this as for some reason I have trouble steadying my hands, but that's beyond the point.

When I switched over from my A300 to the A77 Mk2, I started to notice noise in my photos. I took it in, and they disabled the setting (along with the enable Distort Comp), I found the images were cleaner.

However, just recently (like mins ago), it was bugging me "is this doing what I think it is". So I ran another test run, and found that while small, I did see detail lost with the setting enabled (saw what was pencil erasings or like on an item, they were crisper with the setting off).

So I have noticed that there is more noise with this setting enabled, and while small, it was enough to bug me.