Old camera model

#62

@agriggio’s link covers that. Fortunately, you don’t need RawDigger to examine your raw files.

I wouldn’t do that if I were examining the raw file. And as I and then others have indicated, I wouldn’t process with the base curve most of the time, esp. if you are using filmic.


Other remarks

1. It is entirely possible that your metering is broken. It is not unusual but don’t assume it is so right away.

2. Metering is tied to focusing (and possibly WB). You can separate the two for composing if you prefer a feature like back button focus, etc.

3. Metering is tied to the histogram (or the live view), which is unfortunately the case for all cameras tied to the JPG preview, not the raw file.

4. Due to point 3, your metering would be off say about 1-1.5 EV if your goal is to do ETTR. We call that headroom. For less technical photographers, the headroom actually protects them from overexposure; it is a good thing unless you know what you are doing.

5. Use Manual mode. That way, you get full control over your settings. The are many settings to turn off if you want your live preview to reflect the raw output as much as possible.

6. I had other things to say but I forget… :stuck_out_tongue:

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#63

The problem is evaluative metering, you can’t really count on it as a base for personalized exposure. If you need to be precise measuring the light then you’ll have to resort to center-weighted or spot metering.

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(Gustavo Adolfo) #64

Not sure what you mean.
It is probably the cheapest card in the market. It’s only a cheap cardboard. But it’s sold as 18% grey, for photography.
Not sure why you’ve pointed to a 12% grey, although I’m aware of the 12 x 18% grey dispute (although I don’t understand it :thinking:).

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#65

If you are really pedantic, not all materials are equal and useful in all situations. :wink:

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(Gustavo Adolfo) #66

Thanks @afre for your comments.
Fyi, I turned off every possible setting that might be pushing the image from the neutral stance, although I’m not looking at the camera’s histogram. (But it’s good information knowing that the in camera histogram comes from the jpg)
As for point #1, that’s the one I’m trying to discard, although I agree with @shreedhar that even if the metering presents a bias I can compensate for that.

That’s what I thought it could mean, and probably it isn’t the best one. But even so, would it cause more than one stop shift, like it seems to be the case?

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(Gustavo Adolfo) #67

One thing: doens’t this dcpreview post explain what I need to understand but can’t?

https://www.dpreview.com/forums/thread/2938408/37445447

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#69

A bias is normal but a broken meter isn’t. You need to verify.

You need to check your raw files. Each stop should represent a doubling or halving of the raw values. I am sure you know how to stop up or down with aperture, shutter speed and ISO…

It depends on how your camera meters; and how consistent the material is under various conditions, along its surface, and how reflective and opaque it is, etc., etc. The key is to know your material so that you know what to expect when viewing the raw file. If your values don’t match your expected value by a lot, then you know that something is amiss.

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(Gustavo Adolfo) #70

:blush: yes, I know, although I haven’t been using that since I had my SLR, back in the nineties…

EDIT: Rest sure that for the grey card pics I took, the camera was correctly set up. (In D5, no blinking shutter speed / aperture indicator.)

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(Glenn Butcher) #71

That was fun… I opened _MG4250.CR2 in rawproc, with rawdata=1, so no processing at all was applied. Your camera produces 12-bit raw data, so your maximum value is 4096. libraw says your camera’s min black is 128, but the dcraw adobe_coeff entry says 0, so we’ll just assume dcraw is correct and your camera has a 0-4096 data range.

The image appears to be a full-framed neutral tone, no borders, no other stuff to influence the histogram. Without white balance, the gray tone appears to be at about 518, with the camera white balance applied it goes to 737 . 18% gray in 12-bit would be 737, so I’d say your meter is right on.

I did all this with rawproc data, which is floating point 0.0-1.0, so I had to do some math to convert back to the unsigned integers delivered by the camera. I also found that a monochrome histogram of the raw data isn’t that useful, better would be RGB collected from the individual values of the mosaic pattern, so I’ll be programming that change shortly…

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(Glenn Butcher) #72

Okay, I think I did this a bit wrongly. I used the max channel values to imply the gray tone, when I probably should have used the means. So, for the opened image without any processing, that mean is 421 (@gadolf, from the rawproc info dialog I averaged the rmean, gmean, and bmean, then multiplied it by 65535 to get the integer value). After white balance, that number is 550, so it’s still about 1/2 stop below the 737 value that is 18% gray for your 12-bit camera.

Others, pipe in if you see other considerations or corrections. A good exercise, has given me pause to think through my histogram mods a bit differently…

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