Partial,spot metering and compensation question.

[James.Thomas]

Hello everyone,

I've been practicing with the different metering modes in different situations to try and get used to which ones suit certain situations since asking your advice a few weeks ago.

Now in a few weeks time my family and me are going to visit some friends in Norway,which will hopefully give me some opportunities usually unavailable in the UK to practice them on.

What I would like to know,is if I use the likes of spot and partial metering to obtain the exposure of certain objects surrounded by the bright snow.
Will I still need to use compensation for the brighter snowy areas to expose it correctly,even though my camera isn't actually metering for them?

Many thanks in advance,

James.

 

[artyman]

Quick answer is no, but what is the tonal value of the subject, your meter will try and get to 18% grey whatever mode it's using. So you would get different results with say spot metering pointed at a bright yellow shirt against a purple one. You have to think about what the camera is seeing and adjust as appropriate, then check the histogram.

 

[James.Thomas]

Right OK I think I'm with you now...

So for instance,the bright yellow subject using spot is more likely to expose the surrounding snow closer to it's proper contrast,and the dark purple subject more likely to make it an off grey colour seems as it's a lot further away from the snows contrast.

Is that correct?

 

[HoppyUK]

A spot reading will measure what is within the circle. It will then make that tone mid grey, whatever it is, which means it will sit around the middle of the sensor's dynamic range - in the middle of the histogam.

If your subject actually is mid grey, that is fine - that's where you want it, and the lighter/darker tones will fall into place either side in their natural position. But if you meter off somebody's bright yellow top, then it will be too dark and the whole scene will be under exposed. Likewise, a dark top will create over exposure.

So the trick with spot metering is to meter off a mid grey (18% grey) target. Once you know, it's usually not hard to pick out a tone like that, or to know that stuff like skin/faces are usually about one stop brighter, grass is often there or thereabouts, tarmac usually not far off - that kind of thing, and then make an appropriate adjustment.

You should always check the LCD/histogram/blinkies to make sure in difficult situations, but that's often hard to see in very bright snowy conditions. Here's a plan, which is an adaptation of spot metering and incident light reading technique.

The palm of your hand is usually 1.3 stops brighter than 18% mid grey. So turn it upside to the light, meter off your palm, and then increase the indicated exposure by 1.3 stops (make shutter speed longer, or f/number lower, or ISO higher). Give it a try, maybe +1 or +1.6 depending on skin colour and how often you wash, but you'll never be far out with that method.