Landscape Photography Exposure, ETTR and Highlight Spot Metering Accuracy

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In this short(ish) video I want to show you why your camera spot meter can be something of a ‘let down’ in exposure terms when you are trying to obtain an accurate highlight reading for your scene.

Most ‘in camera’ spot meters are a lot more imprecise than the user imagines.

Nikon spot meter ‘spots’ are generally 4mm wide. That means 4mm ON THE SENSOR!

On an FX camera the sensor is roughly 36mm wide, so the ‘spot’ actually has a ‘window’ or ‘measuring footprint’ that is 1/9th of the viewfinders horizontal field of view.

And don’t think that because you use a Canon you’re any better off – in fact you’re worse off because Canon spots are a tiny bit BIGGER!

In this example I use a shot taken with a Zeiss 21mm – this lens has a horizontal angle of view of 81 degrees.

So the 4mm Nikon spot has an angle of view equivalent to 1/9th the frame and hence 1/9th the horizontal AoV of the lens, in other words 9 degrees.

Aimed at the brightest highlight in the sky its footprint takes in sky tones that are dramatically less than highlights. So the reading it will give me is ‘darker’ than it should be.

My D800E has it’s highlight clipping/blow point 3.6 stops above its mid tone.

If I then apply ETTR to this reading by exposing at +3 to +3.3 stops it will result in blown highlights.

But if I use a 1 degree spot meter aimed at exactly the same place its much narrower angle sees ONLY THE BRIGHT AREA I’m aiming at. This gives me a much BRIGHTER reading, allowing me to push the exposure by +3.3 stops without blowing any of my highlights.

Hope this all makes sense folks.

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All the best

Andy