Fastest EFCS shutter speed usable on the a7RII?

[l_d_allan]

This is where native vs non-native lenses come into play. For native lenses the camera is aware of the properties of the lens,

Thanks for "digging deep" into this issue. I'd admit that much is "over my head".

I've just started seeing how my Canon EF lenses work with FotodioX adapter. So far, so good (with very limited testing).

However, I did notice that the EXIF mis-identified the lens. It seemed to find perhaps a close match among the Sony lens lineup.

Could that be involved? Is that typical for use of adapters with electronic connections?

 

[uncreativename]

Yesterday I looked at shutter travel time for silent shutter operation on the Sony a7RII. Incidentally, we noted that the electronic first curtain shutter (EFCS) pretty faithfully emulated the acceleration of the mechanical second curtain, at least at 1/500 second.

On the Nikon D810, EFCS stops working at shutter speeds above 1/2000. On the Sony alpha 7 cameras with EFCS, Sony advises against using the capability at fast shutter speeds, but let's the user decide how far to push it.

So, let's push it and see what happens when we take pictures of a high-frequency triangle wave on an oscilloscope with the time base set to 500 microseconds (us) per division.


1/1000, mechanical shutter


1/1000 EFCS

You can see that the EFCS image has a little less exposure at the top of the image, but you probably wouldn't notice that in a real photograph. The all mechanical image is pretty even.


1/2000 mechanical


1/2000 EFCS

Now the EFCS exposure is suffering from nonuniformity noticeably, but would probably be fine for many purposes.


1/4000 mechanical


1/4000 EFCS

The EFCS exposure at the top of the image is about 1/3 of that at the bottom. This should normally be avoided.


1/8000 mechanical


1/8000 EFCS

There is essentially zero exposure at the top of the EFCS image. Not useful.

The synching of electronic and mechanical behavior over time, temperture, wear, and sample variation is an iffy business.

I used to say that users should avoid a7x EFCS shutter speeds of over 1/2000 second. Based on these results, I'm dropping that to 1/1000.

--
http://blog.kasson.com

Thank you for this. It's a shame there's not a quick way to disable it. I hope for an automatic option at certain shutter speeds

 

[JimKasson]

Thank you for this. It's a shame there's not a quick way to disable it. I hope for an automatic option at certain shutter speeds

I would be afraid that Sony would design the automatic option so that it turns off EFCS with non-native lenses, which would definitely be throwing the baby out with the bathwater.

Jim

 

[JimKasson]

Thank you so much for doing all this great work.

Jim

 

[Horshack]

Based on my testing, native lenses still suffer from exposure errors at the end of the frame (and intra-frame), which implies that only the interval between the EFCS ending and MSCS starting is dynamic - the rate of the EFCS reset itself is constant.
For non-native lenses the camera has no information about the potential magnitude of oblique light rays from one exposure to the next. For such lenses I believe the camera is using a hard-coded default interval between the EFCS and MSCS, an interval that will work well for certain apertures but not others. This is supported by experiments performed in this thread, where the same lens performs well at certain apertures but not others, with respect to underexposure at the start of the frame. For example as depicted in the full-field exposure error chart data:

Full-Field EFCS Exposure Error Graphs, Sony 55 FE vs Mitakon 50

Revision to the first paragraph above. I actually do see evidence that the EFCS timing varies during the exposure rather than just at the start of the exposure - and this change would actually be necessary because just changing the timing of the start of MSCS would simply change the overall exposure rather than correct peripheral exposure errors at the extreme ends of the sensor.

The evidence of dynamic intra-frame EFCS timing are the exposure bands present at certain apertures. For example, here's a full aperture series of the Sony 55 FE (animated GIF, 5 seconds per frame):

Sony 55mm FE @ 1/8000, EFCS Exposure Error Heat Map for full-aperture series

I believe each diffuse exposure band in the images represents a timing change of the rolling reset of the EFCS, and it varies by aperture. Again, this would be done to allow the timing to accommodate peripheral exposure errors while not altering the overall exposure.

 

[sebbe]

If I would have known that earlier

Thanks for your researches!

 

[J A C S]

More examples here:

http://www.dpreview.com/forums/post/55600402

 

[Neuropsychology]

I always shoot my portraits with EFCS off

 

[theosudarja]

It's just the delay between closing and opening lens aperture, and being exposed while the the aperture blades still in progressing.

 

[Ewgeniy_77]

Here we are in 2024 and the problem is still the same. ) Here is a photo of the E-FRONT. Now I understand why the bokeh is not all equally round. And some (above the shovel tip) are almost gone. From what I've read here, it looks very much like E-FRONT artifacts, or am I wrong? After all, the shutter speed is quite long.
Camera: Fujifilm X-T5. Lens: Viltrox Pro AF 75 F/1.2. In-camera jpeg. Resolution reduction and size optimization with JPEGmini Pro.

Exposure time 1/125 s
Aperture 2.0
Focal length 75 mm
Focal length (EQ35mm) 113 mm
Sensitivity 2500
Exposure bias +1
Metering mode Pattern
White balance Automatic
Exposure program Aperture priority



--
Beginning photographer

 

[J A C S]

Those small ones could be flare. The rest are due to mechanical vignetting.

 

[Ewgeniy_77]

Thank you for the answer. So I'm wrong about E-FRONT and it can be used for continuous CL shooting?

 

[AlephNull]

Here we are in 2024 and the problem is still the same. ) Here is a photo of the E-FRONT. Now I understand why the bokeh is not all equally round. And some (above the shovel tip) are almost gone. From what I've read here, it looks very much like E-FRONT artifacts, or am I wrong? After all, the shutter speed is quite long.
Camera: Fujifilm X-T5. Lens: Viltrox Pro AF 75 F/1.2. In-camera jpeg. Resolution reduction and size optimization with JPEGmini Pro.

Exposure time 1/125 s
Aperture 2.0
Focal length 75 mm
Focal length (EQ35mm) 113 mm
Sensitivity 2500
Exposure bias +1
Metering mode Pattern
White balance Automatic
Exposure program Aperture priority

This very old thread was about exposures from 1/1000 to 1/8000

Your exposure is 1/125 - far below the speeds they were discussing.

Not something for you to worry about here.

 

[Ewgeniy_77]

Your exposure is 1/125 - far below the speeds they were discussing.

Not something for you to worry about here.

Thanks for the answer. That's good, but I'm more concerned about this: Different distances at the start of exposure and on the sensor surface, and when the second curtain closes the sensor. Or is this effect also not noticeable at shutter speeds greater than 1/1000, i.e. 1/125-1/1000?



--
Beginning photographer