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Thread: LCC exposure evaluation when using film curves...

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    LCC exposure evaluation when using film curves...

    Hi,

    My assumption has been, when trying to create the "best" LCC possible, that I should be evaluating the histogram while using a linear film curve, rather than any other curve (Leaf Portrait, Product, etc..). And that this curve should fall on the right side as much as possible, without blowing anything out... Right?

    I ask because I typically do not use the linear curve for my "real" (non-LCC) shots; I prefer one of the other film curves to give it the look I am after. And, it seems that when using these other film curves (Leaf Portrait, Product, etc..), they "boost" the exposure by about a stop or more.

    Yet the problem (I think) when using one of these film curves while evaluating an LCC is that they may make the histogram appear to be towards the right side, yet if you switch to a linear curve, the histogram then falls in the middle, or possibly even a little to the left (and is not "optimal?").

    Along a similar line, another question I have is if it would make sense to expose my scene for my "real" (non-LCC) images according to the histogram when viewing it with a linear curve. And then, when I switch to the curve profile I want for my "look" (eg. Leaf Portrait), I can drop the exposure by a stop to bring the histogram back under control. Wouldn't this provide a better exposed image overall? I just have this feeling that the Portrait Film Curve is really an under-exposed image and is tricking me, and that I should rely on the linear curve for exposure evaluation.

    I did find a tech reference file from the Mamiya Leaf website on LCC creation; however, it doesn't reference film curves and simply states that a histogram for an LCC should be between -0.4 and +0.8... And on this forum, I have viewed posts from Yair saying that it is best to have the right side of your histogram at +2. I'm just trying to sort out the current best practice.

    For reference, I use an Aptus 22 on an Arca Swiss M Line and am viewing the files in Capture One. Many thanks in advance for your help.

    Foster

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    Re: LCC exposure evaluation when using film curves...

    Don't worry if the LCC is not exposed optimally ETTR, if it's in the middle or even a little bit dark there's no problem, the noise will be smoothed in the process. So the coarse rules of thumb you've read is certainly adequate.

    The linear curve will give you a better view of the "actual" exposure though if you're curious, even better if you open it up in say RawTherapee (there you can toggle a raw histogram if you want) or RawDigger.

    Concerning exposing the real images, the profiles are tuned to work with the film curves, so what looks good with them is a good exposure for capture one. It is true though that there can be a bit of "unnecessary" highlight space, so in high DR lighting situations when I shoot landscape with my Aptus I overexpose a bit, and often the actual raw file is not overexposed. The histogram in the back is luminance-based though so you can't really trust it 100% for raw clipping, so if I overexpose a shot I also make another one which is not.

    I process my files almost exclusively in RawTherapee and Lumariver HDR though, so I suggest you check also with someone that knows more about how Capture One works.

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    Re: LCC exposure evaluation when using film curves...

    Torger,

    Yes, as you say the "actual" exposure is what I am curious about. Coming from a film background and having used (and being very comfortable with) my spot meter to evaluate and calculate exposure for film, I have found the non-Linear Film Curves to be a bit misleading, in terms of exposure. At least from what I have been used to. I will now consider the Linear Curve to be the better indicator of actual exposure.

    Thank you very much for the reply, I do appreciate it. As a side note, I found many of your articles (second-hand MFDB Guide) and posts to be very informative for me, and very helpful.

    Best,
    Foster

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    Re: LCC exposure evaluation when using film curves...

    Agreed. You're worrying far too much.

    1) Don't clip the highlight.
    2) Try to be above middle gray (on a standard film curve).

    Of those only #1 is critical. #2 is somewhat optional. It's ideal for perfect correction of color and falloff, but even if you underexpose two stops you'll find the LCC does a very decent job.

    By the way, these comments rely on the fact you're using Capture One. The cast correction routine in Leaf Capture was far more sensitive to proper illumination.
    Doug Peterson , Digital Transitions | Email
    Dealer for: Phase One, Mamiya Leaf, Arca-Swiss, Cambo, Eizo, Profoto
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    Re: LCC exposure evaluation when using film curves...

    Doug,

    Interesting that LCC in Leaf Capture is/was so much more sensitive than Capture One... I wasn't aware of that, and it explains some of the variance in the posts I was reading on LCC exposure techniques... Thank you for that.

    Foster

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    Re: LCC exposure evaluation when using film curves...

    Color cast is a smooth phenomenom which means that you can smooth the LCC image, ie the noise in it will be smoothed and thus it's not so noise sensitive. However, if you also want to cancel out dust spots those need to be in full resolution. I don't know exactly how C1 has implemented their algorithm but I would guess that they have a multi-resolution algorithm, ie color cast smoothed and bring in the dust spots full resolution, while probably leaf capture would do the whole file in full resolution and thus get more noise sensitive.

    In the small spots where dust is cancelled out it's probably still an advantage to have a low noise LCC also in Capture One.

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    Re: LCC exposure evaluation when using film curves...

    My observation is that Leaf Capture is far better in cancelling out dust spots.. In C1 the dust spots become somewhat visible again when making high contrast B&W for instance..

    I also feel that Leaf Capture is better in removing any lines caused by the different read outs from the sensor.

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    Re: LCC exposure evaluation when using film curves...

    That also indicates that Leaf does use higher resolution in their algorithm. I've implemented a LCC algorithm myself which is in Lumariver HDR, there we identify dust spots and separate those out in full resolution, and do smoothing on the rest. Haven't compared LCC performance with C1 though, but at some point I will. I like to compete :-)

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