A question of compensation - August
 

I thoroughly enjoyed the SLR College on metering modes, which reminded me of some of the basics. I did have a thought and a query.
The thought was that when talking about trade-offs in high contrast scenes, perhaps bracketing might have been mentioned. I know it opens up a whole new can of worms about HDR, but that would, surely, be the solution?
The query is relating to "A question of compensation". The box uses a subject which has mainly light tones. The advice is "Here you will need to dial in +1 or +2 compensation. With subjects that are dark in tone, negative compensation will be needed". Surely the oposite on both of these? If the subject is too bright, I dial in negative compensation.
Bob

You are, of course, right, Bob! Bright subjects will need exposure compensation of -1 or -2, and dark subjects will need +1 or +2. Good spot!

We also mistakenly called a B17 Flying Fortress, a Lancaster in the Apprentice feature! Oops! We've had a lot of e-mails about that one!

Huh? While your exposures will obviously need less stops in the light areas and more stops in the dark areas, that's just basic exposures..... when we talk about [B]exposure compensation[/B] it's for a different problem. Don't forget that your camera will try to give you a grey or midtone from whatever it sees in the meter. If I'm out in the snow it will give grey (or blue) snow, so I need about 1.5 stops [B]EXTRA[/B] exposure for white snow. If I'm in a coal mine the camera will, on its own, give me an exposure for grey.... if I want black coal I need about 1.5 stops [B]LESS[/B] exposure.

Yep, agree with GeoffWessex, for bright subjects, add exposure compensation and for dark subjects deduct exposure compensation. Your camera is going to try to make everything a mid-grey so you need to convince it the subject is white/black and not Man at C&A (that will test your music knowledge).

[QUOTE=GeoffWessex;19817]Huh? While your exposures will obviously need less stops in the light areas and more stops in the dark areas, that's just basic exposures..... when we talk about [B]exposure compensation[/B] it's for a different problem. Don't forget that your camera will try to give you a grey or midtone from whatever it sees in the meter. If I'm out in the snow it will give grey (or blue) snow, so I need about 1.5 stops [B]EXTRA[/B] exposure for white snow. If I'm in a coal mine the camera will, on its own, give me an exposure for grey.... if I want black coal I need about 1.5 stops [B]LESS[/B] exposure.[/QUOTE]

Indeed, that is true but I thought Bob was referring to the subject being over-exposed and therefore reducing the exposure so there was no clipping on the highlights end? The box-out mentions your mid-grey average and how to compensate however. And now I've managed to confuse myself! :rolleyes:

[QUOTE=Carly Drew;19821]Indeed, that is true but I thought Bob was referring to the subject being over-exposed and therefore reducing the exposure so there was no clipping on the highlights end? The box-out mentions your mid-grey average and how to compensate however. And now I've managed to confuse myself! :rolleyes:[/QUOTE]Me too.
I only shoot in RAW, which may make a difference - the camera doesn't try as hard (At all?) to compensate, except that ISO is on "A", so it does try to balance (on "P") Aperture Speed and ISO.
If I take a photograph of a White sheet of paper (With or without Garlic), the histogram finishes up on the right. I give Negative compensation and clipping is eliminated.
In Photoshop, I sort out White Balance and because it isn't clipped I get a good picture.
I am clearly missing something?
Bob

I used to shoot Velvia 50 slide film before going digital and got into the habit many years ago of locking exposure on a midtone area. I still find myself doing that now and find it works well for me. Slide film, like digital, was notorious stuff for clipping shadows or highlights and one had to be careful of doing either. Compensation was the norm in most instances. Shooting raw does give a better dynamic range than shooting jpegs, and for that reason raw is a no brainer to use. Shooting to the right is best as it is easier to recover detail from the highlights than it is from the shadows. You can use a grey card, the palm of your hand, or the grass beneath your feet as your midtone. Tweaking the raw from this stance should be a breeze.

Shooting to the right and reducing exposure in ACR does seem to give better results than the original digital advice of exposing for shadows and dragging the slider right in RAW conversion.

[quote=AndyStevens;19866]Shooting to the right and reducing exposure in ACR does seem to give better results than the original digital advice of exposing for shadows and dragging the slider right in RAW conversion.[/quote]

You might find this short essay interesting Andy. It is one that I have posted before. [URL]http://www.luminous-landscape.com/tutorials/expose-right.shtml[/URL]

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[QUOTE=Forseti;19877]You might find this short essay interesting Andy. It is one that I have posted before. [/QUOTE]Since this runs contrary to all the advice I have previously received and also since it doesn't seem to make sense, perhaps you could help me understand.

It is contrary to previous advice, in that data lost in highlights is so terminal that the recommendation has been to shoot "Left of centre" on the histogram, since there is more chance of recovering data in shadows. (My experience reinforces that -a picture with a bright window and harsh shadows can only be recovered in the shadows).

The bit that doesn't somehow seem to make sense in the essay is the assumption that the 4096 discrete tonal values are shared between the F-stops. That suggests that if I shoot at f2.8 I will get 2048 levels, whilst at F32 I will have 128levels. Or have I misread it? If I haven't misread it then frankly I find it hard to believe. The F stop is a mechanical thing, changing the amount of light that reaches the sensor. So the amount of light hitting it will increase / decrease, but why would that change the dynamic range (The frequency / colour) of the received light?

I hope I'm not boring anyone - :confused: - this is important stuff and if I am deluded I would like to know it!