Raw Histograms

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Graham
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#1
Been meaning to ask this for ages and another thread has just reminded me.

I think I'm right in saying that there aren't any cameras that display raw data on histograms. All are subject to a jpeg conversion of some description even if you shoot raw only. For this reason, if shooting raw, I've generally adjusted picture profile to be as flat as possible.

But I'm curious about the technical reasons why we can't see raw histograms or at least have a definitive indicator to warn of blocked shadows or blown highlights in the raw data.
 

Canon Bob

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#2
I think I'm right in saying that there aren't any cameras that display raw data on histograms. .
I believe that Leicas have histograms based on the raw data.

But I'm curious about the technical reasons why we can't see raw histograms or at least have a definitive indicator to warn of blocked shadows or blown highlights in the raw data.
My Pentax 645Z (when used in Liveview) diplays raw based "blinkies" and also superimposes a clipping line on the histogram....both from the "anticipated" raw data (ie, from the precapture sensor reading)
 
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gad-westy
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#3
I believe that Leicas have histograms based on the raw data.



My Pentax 645Z (when used in Liveview) diplays raw based "blinkies" and also superimposes a clipping line on the histogram....both from the "anticipated" raw data (ie, from the precapture sensor reading)
That's interesting as I'd sort of assumed there must be a technical limitation that prevented it but obviously not. So I wonder why it isn't more mainstream.
 

Canon Bob

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#4
It may be down to the chosen colour space which will clip earlier than the sensor. There's no advantage to showing the real limit if the colour space can't display it.
 
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#5
That's interesting as I'd sort of assumed there must be a technical limitation that prevented it but obviously not. So I wonder why it isn't more mainstream.
It is probably less processor heavy to take it from the jpeg. And for most people more meaningful.
But you would expect those cameras aimed at the pro and advanced market would give it as an option
 
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Craig
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#6
Back in the day with forums like luminous landscape and Cambridge in colour advocating extreme 'expose to the right' technique people would modify the picture modes to get the histogram as accurate as possible.

For example they would take the 'neutral' or 'faithful' (Canon) / 'flat' (Nikon) and tweak it to utterly reduce the sharpness, contrast and saturation to negative values.

Then they could push the exposure all the way to the right without the in camera jpeg engine stretching the histogram by adding any of the above.

This 'ETTR' raw file in post production was usually darkened using the exposure slider before any of this was added back in to avoid clipping. Seems pointless but signal to noise ratio had been maximised...

I don't do the above, because I like the review of the image to show me some of the natural contrast and colour, which may well affect how I want to compose the image etc. Also modern sensors are better and blowing highlights is a risk not worth taking to that extreme.

I would recommend using an unmodified neutral profile instead of a 'standard' or 'vivid' for example if you want a more accurate histogram though.
 
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#7
Back in the day with forums like luminous landscape and Cambridge in colour advocating extreme 'expose to the right' technique people would modify the picture modes to get the histogram as accurate as possible.

For example they would take the 'neutral' or 'faithful' (Canon) / 'flat' (Nikon) and tweak it to utterly reduce the sharpness, contrast and saturation to negative values.

Then they could push the exposure all the way to the right without the in camera jpeg engine stretching the histogram by adding any of the above.

This 'ETTR' raw file in post production was usually darkened using the exposure slider before any of this was added back in to avoid clipping. Seems pointless but signal to noise ratio had been maximised...

I don't do the above, because I like the review of the image to show me some of the natural contrast and colour, which may well affect how I want to compose the image etc. Also modern sensors are better and blowing highlights is a risk not worth taking to that extreme.

I would recommend using an unmodified neutral profile instead of a 'standard' or 'vivid' for example if you want a more accurate histogram though.
I always use an unmodified neutral profile as I shoot raw. And though I will make changes during processing at least there is always sufficient headroom in the highlights and shadows to do so.
 
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gad-westy
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#8
Back in the day with forums like luminous landscape and Cambridge in colour advocating extreme 'expose to the right' technique people would modify the picture modes to get the histogram as accurate as possible.

For example they would take the 'neutral' or 'faithful' (Canon) / 'flat' (Nikon) and tweak it to utterly reduce the sharpness, contrast and saturation to negative values.

Then they could push the exposure all the way to the right without the in camera jpeg engine stretching the histogram by adding any of the above.

This 'ETTR' raw file in post production was usually darkened using the exposure slider before any of this was added back in to avoid clipping. Seems pointless but signal to noise ratio had been maximised...

I don't do the above, because I like the review of the image to show me some of the natural contrast and colour, which may well affect how I want to compose the image etc. Also modern sensors are better and blowing highlights is a risk not worth taking to that extreme.

I would recommend using an unmodified neutral profile instead of a 'standard' or 'vivid' for example if you want a more accurate histogram though.
This is really what I’m getting at. We use work arounds to try to get as close as we need to buy it seems strange that we can’t just use the raw data.
 
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Chris
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#9
I shoot RAW+JPEG, with contrast and saturation turned down a bit. Not to get closer to what a RAW histogram would look like, although it does, but simply to give me more room for adjustment of the jpeg image before I need to go back to the RAW. I only use the RAW when easy tweaks to the jpeg don't go far enough, and processing RAW images takes me much longer, so this reduces my image processing time.
 
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Nightmare
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#10
I found a solution to this with my Canon. Use a very flat profile such as faithful or neutral and AdobeRGB. Or even better download one of those log video profiles and use that. The clipping points are now much closer to the real deal. You can go even further with dynamic light optimisation crap but it may actually do something with the RAW file so I leave if off.
 
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Jasmine
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#11
You can set the histogram to display exposure levels from the raw image data on some Canon models using Magic Lantern firmware, some Nikon I think too, the model range availability is limited obviously.
 
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#13
Interesting. Which models?
Canon 5DMKIII for one. I am not so sure of the others. But I must apologise, I edited my posts before posting but didn't realise I had deleted an important parts. This is not using the Canon firmware this is with another firmware, Magic Lantern.
 
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#14
The camera cannot display a histogram of the colour levels of a Raw file as there are no colours yet. The colours only appear after demosaicing in the Raw convertor and the camera has no way to know which Raw convertor you will use or which algorithm the Raw convertor will use. The camera also cannot know how the undemosaiced image will eventually fit into the colour space that is used. My Canon camera only offers sRGB and AdobeRGB whereas I generally use Prophoto colour space.
 
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Richard
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#15
A Raw histogram would be handy, but it's not essential and there's an easy and reliable workaround. I also think there's some truth in what John M says above.

However, it's the work of a few minutes to take a suitable test shot* and note where the highlights are just clipping. Then up-load to your software and increase exposure so that the clipping patterns match - that's how much headroom you've actually got above the in-camera histogram/blinkies and it should be a constant so you can simply apply extra exposure accordingly. It'll probably be around 1-1.5 stops extra in my experience.

In-camera adjustments to Pictures Styles etc can and do affect the histogram, but it's only the Contrast setting that makes a really significant difference worth noting, by slightly stretching the histogram. Again, easy to check and compare as cameras vary (use tripod, and flash for consistency).

*Edit: include a large area of white and adjust exposure so that blinkies are just beginning to flash over the very brightest areas.
 
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Nightmare
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#16
probably be around 1-1.5 stops extra in my experience.
with VIDEO-X aRGB on 5d3 I got to within around 0.5 stop. 1.5 is probably the standard mode if that. 5D3 just doesn't have that crazy highlight recovery latitude if you are doing it cleanly in all three channels.
 
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