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Thread: A boring but possibly useful shot (A7RII)

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    Subscriber Member tashley's Avatar
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    A boring but possibly useful shot (A7RII)

    After all the excitement of 'Lloydgate' and having myself experienced the way in which the camera can hold RAW highlights far better than the histo, blinkies or zebra imply, I did a little test. The following image had to be exposed at -3EV to stop there being any sign of zebra (set at 100+ and with other video settings at defaults) but I then shot it at all compensations allowed, up to +2, and the first file that shows no clipped highlights (or shadows for that matter) in LR was at -1/3rd, which is 2.66 stops headroom above that suggested by the zebra.

    I've been using a rough rule of thumb that I have about 1.5 stops headroom over the 'blinkies' up until now. Here, the blinkies kick in at -2, whereas -2.3 has no blinkies. So that's two stops better headroom than blinkies in terms of headroom.

    So, given that even though Zebra is basically a video feature but is also pre-shot rather than post-shot and therefore more useful, I am going to experiment with the technique of dialling compensation in negatively with this sort of scene (dark areas but with highlights I want to preserve) until the zebra disappears and then dialling it back up by 2.33 or 2.66 stops. Clearly this depends on the profiles and effects you have set up for video shooting but for me this is a starting point that could be useful.

    What do others think?

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    Senior Member mjm6's Avatar
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    Re: A boring but possibly useful shot (A7RII)

    Tim,

    I presume the window frame was saturating first in this image?

    I think that the zebra highlights can be difficult to be universally addressed in this manner, or possibly that you may not want to push it as tight to the limit.

    I believe these appear when you have saturated a channel (any channel), and then you have the buffer built in, which is what you are trying to eliminate somewhat. However, a channel can saturate even if the pixel isn't white looking (think blue sky, or a blue lake maybe?), and therefore you have to be somewhat careful, because a saturated channel is difficult to overcome, and you may be prone to posterization problems as you approach the limits of that saturated channel when you make adjustments to the image later on.

    I generally will go up from the zebras about 1/2 stop or so in the exposure, but I don't typically go up any higher because I don't want to have a channel saturated.

    It does seem that the v2 camera has a nicer shoulder in the response curve than the original a7r, so you may be able to take your approach just fine, but I would be thinking about doing some careful testing to make sure that you aren't going a bit too high with the exposure compensation.

    ---Michael
    a7r, a7rII, FE 16-35, FE 24-70GM, FE 70-200, Loxia 21mm, 35mm, 50mm

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    Re: A boring but possibly useful shot (A7RII)

    Tim,
    Useful test. I hadn't thought about using Zebra settings but it makes sense. I don't shoot video so never paid any attention to Zebra.
    With Canon 5DIII I used the blinkies on the LCD to help with exposure compensation. I found that if I was starting to get blinkies on a bride's dress it was perfect since there was about 1.5 EV of headroom from their in the raw file.

    Haven't even checked to see how to set blinkies on the Sony. Just seeing the quick review image is enough to confirm that I'm good.

    My approach to digital has been similar to transparency exposure. i.e. making sure I have highlight detail then let the shadows fall where they may. With Fuji XTrans and the Sony I've found that its hard to get the shadows to blockup. Even i bright sun. Especially with the later releases of Lightroom. If I'm suspicious about dynamic range I set the camera to auto burst then pick the file that works best. Or, if necessary merge them to HDR in Lightroom.

    I've also built a custom camera profile that applies a linear tone curve when importing the raw file into Lightroom. That offers another option for processing with the highlight details, as well as shadow details well below clipping point in Develop Module unless the file is really off exposure.

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    Re: A boring but possibly useful shot (A7RII)

    Quote Originally Posted by tashley View Post
    After all the excitement of 'Lloydgate' and having myself experienced the way in which the camera can hold RAW highlights far better than the histo, blinkies or zebra imply, I did a little test. The following image had to be exposed at -3EV to stop there being any sign of zebra (set at 100+ and with other video settings at defaults) but I then shot it at all compensations allowed, up to +2, and the first file that shows no clipped highlights (or shadows for that matter) in LR was at -1/3rd, which is 2.66 stops headroom above that suggested by the zebra.

    I've been using a rough rule of thumb that I have about 1.5 stops headroom over the 'blinkies' up until now. Here, the blinkies kick in at -2, whereas -2.3 has no blinkies. So that's two stops better headroom than blinkies in terms of headroom.

    So, given that even though Zebra is basically a video feature but is also pre-shot rather than post-shot and therefore more useful, I am going to experiment with the technique of dialling compensation in negatively with this sort of scene (dark areas but with highlights I want to preserve) until the zebra disappears and then dialling it back up by 2.33 or 2.66 stops. Clearly this depends on the profiles and effects you have set up for video shooting but for me this is a starting point that could be useful.

    What do others think?

    Sounds good but wouln't it be dependent on colour balance and your profile settings (i.e. contrast, colour space, saturation)

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    Re: A boring but possibly useful shot (A7RII)

    Tim. Great minds and all that!! I hadn't seen this thread but had just watched the video part of the reviewof the A7rII on the LuLa website and they talked about zebra a feature I have never used so tried it out and came to basically same conclusion as you, -2 and then dial back seem to show that there is a 2 stop headroom but I Have to say that it is a bit of a cumbersome way of going about it and wish that it could just be more accurate and linked to the RAW file in the first place. An interesting eperiment but I will probabaly rely more on my judgement as I find these thing to be very distracting when trying to compose

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    Subscriber Member tashley's Avatar
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    Re: A boring but possibly useful shot (A7RII)

    Quote Originally Posted by timparkin View Post
    Sounds good but wouln't it be dependent on colour balance and your profile settings (i.e. contrast, colour space, saturation)
    Yes, which is why they are all at defaults (other than setting colour space to Adobe)...

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    Re: A boring but possibly useful shot (A7RII)

    Quote Originally Posted by tashley View Post
    Yes, which is why they are all at defaults (other than setting colour space to Adobe)...
    Doh! I read that too fast obviously ;-)

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