histograms

[Tom Alicoate]

Another important point: if you shoot raw, your histogram is lying. It is based on the JPEG, which is often one, two, or even three stops over- or under-exposed relative to the true raw data. The reason for this is that the saturation, curves, space conversion, contrast, and especially white balance processing all affect the histogram, even though they don't affect the raw data.


Here's an example:


[url="http://forums.dpreview.com/forums/read.asp?forum=1037&message=26905476]http://forums.dpreview.com/forums/read.asp?forum=1037&message=26905476[/url]


Until manufacturers add a raw histogram feature, the only workaround is to build a custom white balance file that reverses the effect of the in-camera processing to give you a *real* histogram. Some call that a "Uni-WB". The downside is that the metadata, preview, etc. are all useless (and very green!), so you can't check an image for color tones *and* histogram at the same time.
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I have seen this before too. Usually If I bumped up contrast and saturation I would get a Histogram that was out of whack. Now I reduce the saturation and contrast to zero and the Histograms don't look as incorrect. I only use the black and whitehistogram however. There may be a better way to make this Histogram closer to true. Anybody have any ideas? I don't want to mess with the three color ones if the results are a s bad as you say.


Thanks,


Tom

[Daniel Browning]

There may be a better way to make this Histogram closer to true. Anybody have any ideas? I don't want to mess with the three color ones if the results are as bad as you say.

The only way I can think of would be for a camera manufacturer to add this simple option. Barring that, there is no way you can get close without messing with the colors, because the colors are exactly the reason why it's off in the first place.


Accurate colors or accurate exposure: pick one.

[Kyle Webb]

Adrian,


Below is a link to the Cambridge in Color website that has a couple ofvery good tutorials on histograms, how to read them,and how to use them to improve your images.


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


http://www.cambridgeincolour.com/tutorials/histograms2.htm


By the way this Cambridge in Colour website is an excellent resource.


Kyle

[Don Burkett]

By the way this Cambridge in Colour website is an excellent resource.


Kyle
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It is a very worthy read. Be prepared for disappoint though, becasue when you are done you're going to wish there was more.


He did an excellant job on a number of subjects that helped me understand a number of things much clearer.


Good recomendation Kyle.

[Kyle Webb]

Don,


<span style="font-size: 9pt; color: black; font-family: Verdana;"]As an Opto-Mechanical Engineer I use this <st1:city w:st="on"]<st1lace w:st="on"]Cambridge</st1lace></st1:city> in Colour website recourse all the time. It is an especially good reference source for technical reports and presentation in explaining optical phenomenon related to digital photography as well as optical phenomenon in general. The beauty of it is that they explain theory and show practical applications and results of the phenomenon. I am glad that you can appreciate it.


<span style="font-size: 9pt; color: black; font-family: Verdana;"]Kyle<o></o>

[Stefan Stuart Fletcher]

I've learnt a lot from all the posts in this thread. Thanks to everyone for contributing. One other thing: the histogram in PP software such as ACR or Lightroom is not quite the same as the camera's (especially if you shoot RAW), but can be used to correct overall exposure and tone based on the same principles. Any good book on e.g. Lightroom will provide a thorough explanation. The colour channels are, however, more useful than implied elsewhere. You can use them to check your HSL settings in addition to getting the exposure right.