Confusion over good dynamic range

Mr.Pink

Mr.Pink

Mr.Pink

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Apologies for a newbie question, but it is something that has confused me for a while. I am trying to understand how to get good dynamic range.

As i understand it, if a camera is left on P or Auto, it tries to expose for 18% grey. To get more control, if a compostion is mainly bright colours or lots of whites, i should set the exposure 1 or 2 stops over to try and keep the details in these bright areas. Conversely, if the composition contains lots of dull, or darks and blacks, then i should expose 1 or 2 stops under to try and keep the blacks.

Is that right so far?

What about a very contrasty composition? The most obvious example that springs to mind is the bride and groom shot. Her in her whites dress, and the groom in a black suit. How on earth would you manage that? surely something has to give?
I have seen some awesome shots in here with incredible dynamic range, but never understood how it was achieved.
TIA
 
I read your question the other day and was tempted to reply but didn't want to on my phone :p

So here goes. As I understand it dynamic range can be described in laymens terms as the luminance range, or even brightness range. If you're describing the scene you are shooting then it is the range from the darkest black spot in the frame, to the brightest white spot in the frame. However, you can talk about the dynamic range of your camera, which describes the range/contrast that your camera can physically capture. Your camera wil have a significantly lower dynamic range than your eye. This is why you get crushed blacks or clipped whites in a very contrasty scene.

Here is a simple example off the top off my head. Say in the real world the brightest white is 100% and the darkest black is 0%. Say that your eye can see a 70% proportion of that, anywhere along the scale at one time. So you could look at the black area and see everything from 0%-70%, or you could focus on the brightest area and see 30%-100%. Now say that your camera can only see 30% of that range. That is the dyamic range of your camera and it's with that in mind that you have to set up your shot. If you want to see the darkest elements of the scene you will have to meter (expose for) the 0%-30% range. Of course, everything over 30% will be horribly clipped. Or, you can meter for the top 30% (70%-100%). Then, you'd lose all detail in the shadows. However, what most people would do is meter for the middle 30%. So you'd expose for 35%-65%. You'd then get a 'normal' picture, but of course due to the limited dynamic range of your camera you would still be losing anything under 35% and anything over 65%. Make sense?

So, in practice, and taking your example. You now know that your camera can capture a dynamic range of 30%. When you set up your bridge and groom shot you would need to make sure that the blackest blacks in the shot are lit sufficiently to be within the same 30% range as the brightest part of the dress. Or, you make sure there's not too much light on the dress as that will push the top-end of your dynamic range too high. Essentially when people are lighting shots, unless they're doing something wacky the main reason they are using lights is to squash the scene's dynamic range into that magic 30% so the camera can capture it all.

I hope that helps. In reality that made-up 30% can be properly measured in (f) stops.

This link may or may not help too: http://www.cambridgeincolour.com/tutorials/camera-metering.htm

EDIT: I wrote all that and realised that the most helpful piece of advice I can give is to start reading your camera's histogram after taking a shot! That is the clearest and most concise explanation of dynamic range out there! If you don't know how to read a histogram you should learn!

http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml
 
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Many thanks for the info and the links.

Quite interesting about the histogram. I didn't realise what a useful instant feedback tool it was, in fact i don't think i have ever used it.:o
 
Mr.Pink said:
Many thanks for the info and the links.

Quite interesting about the histogram. I didn't realise what a useful instant feedback tool it was, in fact i don't think i have ever used it.:o
Click to expand...
a lot of people don't - and that's surprising! I'm quite used to looking at that rather than the actual shot a lot of the time.
 
If you're worried about exposure mistakes and don't mind a bit of post work then shoot in RAW if you don't already - it gives you a bit of wiggle room when making adjustments.

It's not a get out of jail free card if you completely screw up but you'd be surprised at what you can rescue sometimes.
 
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