D200 how to avoid over-exposure ?

Started May 26, 2006 | Discussions thread
OP Stefaan De Rore Regular Member • Posts: 132
Re: Spot meter on highlights

tnielsen wrote:

Hi Stefaan

Let's for a moment assume we are talking B&W-photography
18% grey is the tone lightmeters are calibrated to "seing". What
this means is that if you point your camera towards a white piece
of paper covering the whole field of view, and let the light meter
decide on exposure, the resulting image will be 18% grey - sort of
medium grey. If you do the same with a piece of dark grey paper,
the same thing happens: The image will turn out 18% grey. The
lightmeter measures light reflected from the scene and has no
chance knowing whether the scene is dark and well-lit or light and
poorly lit. Does this make sense?

It does make sense. Just wondering why they call it 18% gray but I read somewhere else that this is the percentage of reflection on a gray card

Now if you spotmeter from the brightest part of your scene, the
camera will set exposure as to make the highlights 18% grey. If you
overexpose by one step, highlights will by rendered "one step
lighter" than 18% grey .. and so on. On the D200 an overexposure of
2.7 steps will render highlights completely white - on the verge of
blowing. There is nothing physical about 2.7 .. this is just how
the sensor in D200 behaves .. on the D70 it was more like 2.3

If you say 2.7 renders highlights completely white does this apply to the JPEG or the RAW ?

At higher ISO-settings the dynamic range of the D200 decreases and
you reach the point of blowing highlights sooner.

I hope this made a bit more sense

It does, thank you for the information.

best regards

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