Histogram/zebras - what am I seeing?

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Abrak
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Histogram/zebras - what am I seeing?
2 months ago

I am pretty confused about the histogram and zebras.

1) I understand that the histogram shows a pixel as overexposed when any of its RGB values is 235 (out of 255) or greater (this according to Friedman's book). So shooting raw it maybe blown but may well not.

2) I have zebras set to 100+. I like the zebras because they show which areas of the image risk being overexposed. But I dont have any idea what 100 equates too.

You can see the problem in these 2 photos....

The first shows the histogram and zebras at 0EV. The histogram shows a small area as being 'overexposed' but maybe all is recoverable in post. The zebras seem to show a large area - practically half the image.

At -0.7 EV obviously very little of the image is 'overexposed' but my zebras set to 100+ still show a large part of the image overexposed. If I ratchet down the exposure far enough say to -2.5EV I can get rid of the zebras at which point the histogram is well short of the far right.

So what, in fact does '100' equate to in RGB values?

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