# Y Axis Histogram Clipping Prevention



## decado (Oct 10, 2009)

So I've been noticing while taking a lot of daytime pictures I'm getting clipping on the histogram readouts at the top of the histogram (y axis). Now I know how to get the exposure right to balance the histogram between light and dark, but even if it's right in the middle it's still clipping at the top. How do I stop this clipping?


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## Josh66 (Oct 10, 2009)

Expose less.

But really, it might not matter.  What exactly is getting clipped?  If it's just a few unimportant spots, who cares?


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## decado (Oct 10, 2009)

It seems like a pretty good chunk is getting clipped, and exposing less just shifts the histogram to the left, still clipped at the top. Might a polarizing filter help with this?


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## Garbz (Oct 11, 2009)

Wait no, the Y axis has no scale!

The X axis ranges from shadow clip to highlight clip, but the Y axis is arbitrarily scaled often to give the most meaningful representation of data. It doesn't matter how high the Y scale is, and if it is clipped it also wont matter.


In that respect I'll also add it doesn't matter if the shadows or highlights are clipped too on the histogram providing it is done in a way that doesn't detract from the photo. The histogram is an aid for creating an exposure, it is not something that a good picture must precisely fit into ensuring that no pixel is too light or too dark. Many people seem to forget that in the pursuit of a 100% clip free image.

Here's a good article on histograms: http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml


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## decado (Oct 11, 2009)

Garbz said:


> Wait no, the Y axis has no scale!
> 
> The X axis ranges from shadow clip to highlight clip, but the Y axis is arbitrarily scaled often to give the most meaningful representation of data. It doesn't matter how high the Y scale is, and if it is clipped it also wont matter.
> 
> ...


I get that it doesn't matter if the shadow or highlights are clipped as long as it doesn't detract from the photo, but for most the pictures I've been taking it would. Not to mention I'm shooting in Raw mode so wouldn't getting a fairly neutral exposure be the best for later adjustments?


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## Josh66 (Oct 11, 2009)

decado said:


> It seems like a pretty good chunk is getting clipped, and exposing less just shifts the histogram to the left, still clipped at the top. Might a polarizing filter help with this?



Ah, yeah - you're right, less exposure would just move it to the left more.

I guess to get a picture where nothing goes over the top of the histogram, it would have to be pretty flat.  Almost the same tone throughout the photo.

Seems like that would make for boring pictures...  Not much contrast.

As long as you're not losing excessive amounts of detail (in the shadows, or highlights), I wouldn't worry about it too much.

Nobody else is going to look at the histogram, they're going to look at the photo.  As long as that is good, don't worry about the histogram so much.


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## decado (Oct 11, 2009)

O|||||||O said:


> decado said:
> 
> 
> > It seems like a pretty good chunk is getting clipped, and exposing less just shifts the histogram to the left, still clipped at the top. Might a polarizing filter help with this?
> ...


I do have some great top clipped pictures, I was just under the impression that you would lose detail or have distortion, much like a clipped sound wave.


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## Garbz (Oct 12, 2009)

Shooting neutral in RAW would not, Shooting as bright as possible does, since there is far more data stored in the highlights than the shadows. But then the risk of clipping is so great you often ask youself why bother. 

In any case the Y axis still means nothing. You are looking at a soundwave sideways. If you rotate the sound wave so -0dB is at the right side of the histogram, and -infdB is on the left side of the histogram they become comparable. In this case distortion = losing detail.


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## Josh66 (Oct 12, 2009)

Garbz said:


> In any case the Y axis still means nothing.



What exactly does it represent though?  I understand that you're saying the top of it is meaningless (they have to make it stop somewhere...), but it has to represent _something_.  I always thought it was just showing the amount of data in that particular section (so, I guess more would be better).  Is this correct?


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## Derrel (Oct 12, 2009)

There is no such thing as "Y axis clipping"...the height of the histogram, ie the height of the Y axis representation is based upon how bright the scene is....bright subjects have high Y axis representation because they are, well, bright. But over-exposure clipping is represented on the right hand side of the X axis.

The perfect histogram - How to read the histogram on a digital camera - I know very well that the perfect histogram does not exist, but knowing what to aim for can be a great help. - 500th.net


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## Garbz (Oct 13, 2009)

It shows the amount of data yes, but it is automatically scaled with no indication at all as to how high it is. There is also no rule saying that a histogram needs to represent every pixel, or a portion of pixels etc. If I take two identically exposed frames with two different camera bodies but keeping everything else constant I will get two different histograms. Yes they will have an equalish distribution but they likely won't be the same.

The Y axis is some indicator of how much of that value. But, How much is anyone's guess. Is it linear, logarithmic, or does it have some other curve? Again anyone's guess. That is what I meant by it means nothing. It can give a rough indication of how things compare to each other, but even this isn't constant between representations to the point where if you don't have an image to associate with it you really can't infer more information from it than, hey there's more light than dark areas.


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