Histogram technicalities

[Mitchell]

I would like clarification about a technical aspect of the histogram.

I was told that if you divide the histogram into say 5 sections, the right-most section will include significantly more pixels than the section second from the right. Therefore the left-most section will be represented by the fewer total number of pixels.

I took from this that if you have an image that won't fill the entire dynamic range, you are better letting in more light, thereby push the histogram right (without clipping the whites). You then have the most number of pixels representing the image and you can adjust the exposure in PP.

Can the tecchies tell me whether these two points are correct or am I misguided?

Cheers
Mitchell

[digitor]

You are just a bit misguided - broadly speaking, the number of pixels in the image depends on the sensor in your camera, but you've perhaps just got a bit of a terminology problem.

Here is a good tute on the histogram: http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml

Cheers

[gstark]

You are just a bit misguided - broadly speaking, the number of pixels in the image depends on the sensor in your camera, but you've perhaps just got a bit of a terminology problem.

I don't think that's the question that Mitchell is asking, however.

I think that he's asking about how those pixels are represented in the histogram, and whether there is any weighting of those pixels within the histogram representation. That might happen regardless of the camera's sensor, and it might happen in one brand of camera and not in another, or perhaps in just one model.

TBH, I have never heard of this, and I certainly don't know.

[Mitchell]

I think that he's asking about how those pixels are represented in the histogram, and whether there is any weighting of those pixels within the histogram representation.

Thanks for clarifying my question Gary - that is precisely it. Is there a weighting within the histogram so that a vertical bar on the right of the histogram represents more pixels than the same bar appearing on the left?

[Mitchell]

Digitor - thanks for the link! That page links to:

http://www.luminous-landscape.com/tutor ... ight.shtml

Which gives the answer I was looking for-

If a given camera has a dynamic range of 5 stops, half of the available tonal values are contained within the first stop. ie if you don't use the right fifth area on the histogram, you are not using at least half of the available tonal values.

So I guess exposing to the right is the way to go...

[digitor]

Is there a weighting within the histogram so that a vertical bar on the right of the histogram represents more pixels than the same bar appearing on the left?

No, the height of the bar (the vertical axis) represents the number of pixels at the tonal value represented by the position along the horizontal axis.

Your expose to the right idea was correct though, as you found from the link!

Cheers

[wider]

the easy way to say it (that i heard) is that it is best to expose a little to the right as there is more data in the brighter areas of the histogram in regards to the tonal values.

but watch out for the luminace histogram or blinking highlights, as supposedly most nikons get this value from the green channel only and can misrepresent clipping in other colour channels