# HDR histograms



## Battou (Nov 29, 2008)

...

Can some one explain the HDR histograms to me in laymans terms?

Prolly dosen't help that I don't understand histograms to beginwith but......I wanna know.


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## JerryPH (Nov 29, 2008)

Histograms are histograms as far as I know.  HRD histograms would be more evenly dispursed across the top as what happens during tone mapping or the more aggressive HDR process is that the lower ends of the scene are balanced out.

For more info on reading/understanding histograms:

http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml

http://www.cambridgeincolour.com/tutorials/histograms1.htm

http://digital-photography-school.com/blog/understanding-histograms/

http://www.sphoto.com/techinfo/histograms/histograms.htm

http://www.larry-bolch.com/histogram/

... and google can find you a couple thousand more.


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## Garbz (Nov 29, 2008)

Indeed HDR just implies that an image has more dynamic range. It is still possible to clip both highlights and shadows of a HDR image. The HDR histogram acts just like any other where the right hand side represents saturated whites, while the left represents saturated blacks as the above links explain.


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## Battou (Nov 30, 2008)

Yes, but unless I over looked it it does not explain to me why this histogram looks so ****ed up


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## ann (Nov 30, 2008)

I don't know what you expected but there is nothing so wrong here.

it is fairly continuos toned. a small spike at 255 but doesn't seem to be clipping off 
perhapes i am don't understand what your asking


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## JerryPH (Nov 30, 2008)

Ann, Battou is refering to the massive spiking and peaking.  That is something that under normal photographic histograms *should* raise eyebrows.  This what happens when you start loosing important data and details.

In HDR, this is normal, but is a sign of lost detail and info in non-HDR pics.  People think that HRDs look cool becuase they add some colour and what not, but in fact all you are doing is compressing various aspects of it and that is what the histogram looks like.  The same histogram "effect" can be somewhat duplicated by playing with contrasts and levels a lot (in effect, make the picture look crappy in a non-HDR pic... lol)

I just did something pretty funny/stupid... I was looking at the histogram above and then clicked on the CLOSE button... frowned and right away chuckled at myself for trying to click on a picture of a close button... I am such a clutz sometimes.  :lmao:


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## ann (Nov 30, 2008)

sorry, i was clearer, i realized this spikes occur with hdr images.


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## Fiendish Astronaut (Nov 30, 2008)

Do the spikes really occur because it is an HDR. I think it is more because of the degradation of quality as suggested by Jerry. Perhaps the HDR converter will do this everytime but that is probably a symptom of the HDR software re-processing the file and not part of the nature of HDR images themselves.


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## Battou (Nov 30, 2008)

JerryPH said:


> Ann, Battou is refering to the massive spiking and peaking.  That is something that under normal photographic histograms *should* raise eyebrows.  This what happens when you start loosing important data and details.
> 
> In HDR, this is normal, but is a sign of lost detail and info in non-HDR pics.  People think that HRDs look cool becuase they add some colour and what not, but in fact all you are doing is compressing various aspects of it and that is what the histogram looks like.  The same histogram "effect" can be somewhat duplicated by playing with contrasts and levels a lot (in effect, make the picture look crappy in a non-HDR pic... lol)
> 
> I just did something pretty funny/stupid... I was looking at the histogram above and then clicked on the CLOSE button... frowned and right away chuckled at myself for trying to click on a picture of a close button... I am such a clutz sometimes.  :lmao:



I suppose if I had posted the histogram to beginwith this would have been much clearer but yeah, it's the massive spiking that cought me as odd. I don't generally use histograms but have been growing more and more curious. That said, I've been going threw and glancing at them on some of my older pictures and was noticing a bit of a trend but the one above along with a handful of others cought me as different.

So this is fairly normal for an image with a high dynamic range then?


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## JerryPH (Dec 1, 2008)

Yuppers, quite normal.  You cannot expect to tweak a file to the level an HDR is and not get lost data one way or another.


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