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Thread: A7 - EFCS limitations

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    A7 - EFCS limitations

    I was experimenting using very short shutter times today with the A7. At exposure times shorter than about 1/2000 second, a gradient begins to appear at the top of the frame, becoming quite strong by 1/6400 and 1/8000 second. Turning off the Electronic First Curtain Shutter option eliminates it.

    Based on what I know about how EFCS works, I'm pretty sure this is just a characteristic limitation of the EFCS implementation on this camera. Does anyone else have thoughts about it?

    thx!
    G

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    Re: A7 - EFCS limitations

    Yes this is a well known issue. Happens on other bodies with EFC as well (eg Canon 5D)

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    Re: A7 - EFCS limitations

    Quote Originally Posted by mbroomfield View Post
    Yes this is a well known issue. Happens on other bodies with EFC as well (eg Canon 5D)
    Thanks, I thought it must be. This is the first camera I've owned that includes EFCS, I hadn't seen it before. :-)

    G

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    Re: A7 - EFCS limitations

    Quote Originally Posted by johnnygoesdigital View Post
    EFC is an incredibly useful feature.
    I agree. I just want to understand when to turn it off ... :-)

    G

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    Re: A7 - EFCS limitations

    I had to re-write my comment...

    I did not go above 1/2000th, but if I needed higher I would not hesitate to turn it off on the A7. The 36MP of the A7/r might be more sensitive to camera movement because of the smaller pitch and movement of the mechanical shutter that might induce unwanted results with long lenses. My understanding is the EFC is basically a scan with no mechanical connection, a kind of digital MU It's interesting that the A7r does not have this feature when it clearly would benefit from it.
    Last edited by johnnygoesdigital; 23rd March 2014 at 16:38.

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    Re: A7 - EFCS limitations

    Quote Originally Posted by johnnygoesdigital View Post
    The 36MP of the A7/r might be more sensitive because of the smaller pitch and secondary movement of the mechanical shutter that might induce unwanted results with long lenses.
    Unfortunately the a7R does not have EFCS, only the a7.

    Godfrey, can you post the effect in your a7 shots. I've looked at my 1/2000 - 1/4000 th sec shots of my NEX 5 and 6 and cannot see anything, but probably I don't know what I'm looking for

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    Re: A7 - EFCS limitations

    I don't think the smaller sensors have the problem. I've also never seen it on my 5/6 Nex's. Essentially it's just a problem with data transfer speed

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    Re: A7 - EFCS limitations

    Quote Originally Posted by mbroomfield View Post
    Yes this is a well known issue. Happens on other bodies with EFC as well (eg Canon 5D)

    Hmm, I have the Canon 5D, and I do not think it has EFC (electronic front curtain ?)

    Not even sure if it is applicable for that camera since it does not have live view, and hence, the mirror action would take precedence over mechanical front curtain.

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    Re: A7 - EFCS limitations

    Quote Originally Posted by Godfrey View Post
    I was experimenting using very short shutter times today with the A7. At exposure times shorter than about 1/2000 second, a gradient begins to appear at the top of the frame, becoming quite strong by 1/6400 and 1/8000 second. Turning off the Electronic First Curtain Shutter option eliminates it.

    Based on what I know about how EFCS works, I'm pretty sure this is just a characteristic limitation of the EFCS implementation on this camera. Does anyone else have thoughts about it?

    thx!
    G
    Hmm, this is interesting, how did you do the test that found this issue with EFC?

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    Re: A7 - EFCS limitations

    Quote Originally Posted by mbroomfield View Post
    I don't think the smaller sensors have the problem. I've also never seen it on my 5/6 Nex's. Essentially it's just a problem with data transfer speed
    I think the idea behind EFC, is that there's considerably more movement with two mechanical shutters moving back and forth. The EFC scans or blacks out the photosites in the same manner the mechanical shutter would block them, so less movement. With 35mm FF sensors with very small pixel pitch, the movement is more pronounced, especially with longer lenses.

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    Re: A7 - EFCS limitations

    I noticed it first as a darkening of the upper edge of a photo made at 1/6400 second.

    with EFCS OFF:


    with EFCS ON:


    I then tested at all exposures from 1/8000 to 1/800.

    As you can see from this JPEG, https://dl.dropboxusercontent.com/u/...45/EFCS_A7.jpg, the effect can be subtle with a gradient in the image. But on a clear, solid blue sky it was dramatically visible, particularly with a bit of underexposure.

    If you look at the image pairs, it becomes noticeable in the EFCS ON series at exposure times shorter than 1/2500 second. Below that, the difference is not easily discernible.

    G
    Godfrey - GDGPhoto Flickr Stream
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    Re: A7 - EFCS limitations

    It's on the a99 and I have seen suspicious shading on quite a few images, since I shoot in ultra bright conditions at times and love to show the highlight tones the sensor produces.

    It is widely regarded as a totally good thing with very little attention devoted to a decent study by the otherwise forensic web fault-finding community.

    Sony had this to say recently:

    '•If shooting with high shutter speeds when a large diameter lens is attached it is recommended this feature be turned off. Otherwise, some ghosting or blurring may occur.'

    and

    'It is possible that certain areas in a picture that are not in focus may break up, depending on the subject and shooting conditions when using a large diameter lens at fast shutter speeds. Additionally, when using Konica Minolta™ lenses, pictures may not be properly exposed and image brightness may appear inconsistent. In either of these situations, it is recommended to turn off the electronic front shutter.'

    https://us.en.kb.sony.com/app/answer...BzUi1QbA%3D%3D

    There is probably a menu dive needed to do so. Trouble is: you may not notice it on the camera and not be able to revisit the shot.

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    Re: A7 - EFCS limitations

    If you look at the image pairs, it becomes noticeable in the EFCS ON series at exposure times shorter than 1/2500 second. Below that, the difference is not easily discernible.


    It's good you have the option of either...Besides if shooting @1/8000th you might not need EFC anyway.
    Last edited by johnnygoesdigital; 23rd March 2014 at 20:18.

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    Re: A7 - EFCS limitations

    It happens on NEX's as well. Here is an example on the NEX-5N (EFCS on left): Image
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    Re: A7 - EFCS limitations

    Thanks for all the examples, much appreciated.
    I'll take another look at my files.

    Best way to describe it now (for me) is one sided vignetting at the top. I was expecting a more horizontal darkening, so I have learned something new here.

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    Re: A7 - EFCS limitations

    Quote Originally Posted by horshack View Post
    It happens on NEX's as well. Here is an example on the NEX-5N (EFCS on left): Image
    Are you sure it's left? I see a much more vignetted dark sky on the right.

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    Re: A7 - EFCS limitations

    Quote Originally Posted by pegelli View Post
    Thanks for all the examples, much appreciated.
    I'll take another look at my files.

    Best way to describe it now (for me) is one sided vignetting at the top. I was expecting a more horizontal darkening, so I have learned something new here.
    As you can see from the two examples of the trees, it is horizontal. It's just that the subsequent test with the sky shots had a gradient to the illumination that wasn't there in the original capture ... different times of day/cloud conditions.

    G

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    Re: A7 - EFCS limitations

    What can happen - and this is what makes it difficult to apportion 'blame' to EFCS - is that the blue sky in many places has a natural gradient relative to the sun's position, time of day and atmospheric conditions, very often this is left to right (or vice versa) in your chosen composition.

    I have seen this many times and it does not detract from the image, but I see it less with the a7r, so colour me suspicious - for my unusual photography.

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