Monobod
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Reged: 03/04/2003
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Loc: Just West of Norwich, Norfolk
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I have seen photographic examples of this, but not understood the technique. Or is it just another name for High Dynamic Range where several images taken at different exposures are combined. If so, I do understand the technique.
If it is something else, then please enlighten me.
Thanks. 
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David.
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 4200
Loc: Really Here In Name Only
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Surely a "mapping" is just a conversion table from one set of tones to another? Contrast, brightness, gamma adjustment, they're all forms of tone mapping, but not very interesting ones .... they can also be used to make easily visible very small changes in tone, as in the "contour map" type images you often see in astronomy books.
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Meredith
enthusiast
Reged: 23/10/2006
Posts: 242
Loc: Coventry, UK
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Tonemapping is what you do to HDR images to display them on low dynamic range media - monitors/prints etc.
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Meredith Lewis
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Monobod
'Phantom' of the forum!
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Loc: Just West of Norwich, Norfolk
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Quote:
Tonemapping is what you do to HDR images to display them on low dynamic range media - monitors/prints etc.
Not quite sure what you mean here? How else would one display HDR images except on a monitor or as a print? Or are you refering to digital projectors?
We are getting off the subject a little though, I understand the method of taking three or five images with a different exposure value and then combining them in Photoshop to arrive at the final image with everything from extreme highlight to full shadow detail. Is this what is done when 'tone mapping' or is it related to enhancement of selected areas on a single image, which of course is something entirely different?
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David.
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Photos hosted by Flickr.
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Monobod
'Phantom' of the forum!
Reged: 03/04/2003
Posts: 5672
Loc: Just West of Norwich, Norfolk
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Sorry, I should have Googled this before asking. Yes, it is combining three or more images into one HDR image.
See this tutorial:
Tutorial
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David.
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Photos hosted by Flickr.
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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john_g
Pooh-bah Hoo-ha
Reged: 09/05/2007
Posts: 2156
Loc: Surrey
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I bookmarked this a while back because I thought it gave a really good and interesting explanation of HDR photography.
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John
The best things in life are not things.
http://www.flickr.com/photos/john_gass
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Monobod
'Phantom' of the forum!
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Loc: Just West of Norwich, Norfolk
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Quote:
I bookmarked this a while back because I thought it gave a really good and interesting explanation of HDR photography.
Thanks, John. I have circulated this to our club members, it is a good site. I will give this a go and see how I get on with it. There are some really good examples of this technique HERE. These are taken in the RC cathedral in Norwich, worthy of a peek.
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David.
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Meredith
enthusiast
Reged: 23/10/2006
Posts: 242
Loc: Coventry, UK
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Quote:
Not quite sure what you mean here? How else would one display HDR images except on a monitor or as a print? Or are you refering to digital projectors?
You can't view an HDR image on low dynamic range devices (monitors, projectors, prints) properly as the dynamic range is too high. They look very dark in my experience.
You have to tonemap the HDR image into a low dynamic range image to get it looking correct on a monitor etc.. This is what software like Photomatix does.
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Meredith Lewis
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Norman
Reged: 23/09/2004
Posts: 1536
Loc: West London, UK
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Quote:
You can't view an HDR image on low dynamic range devices (monitors, projectors, prints) properly as the dynamic range is too high.
What else is there?
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Regards,
Norman
www.photobox.org.uk
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Adesw
The phantom flasher
Reged: 07/02/2008
Posts: 674
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You can also tonemap a single image to make it into a pseudo HDR image.
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Monobod
'Phantom' of the forum!
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Loc: Just West of Norwich, Norfolk
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Quote:
Quote:
You can't view an HDR image on low dynamic range devices (monitors, projectors, prints) properly as the dynamic range is too high.
What else is there?
If a monitor can display all tones from pure black (255) to pure white (0), what else is there? The camera cannot record anything outside this range, so I am still confused by your statement. HDR is simply a compilation of the best data from both ends, with the detail retained. The limited dynamic range of a camera can either retain highlight detail and block up shadows, or retain shadow detail and burn out the highlights. The monitor can display both extremes, so the combined images display as expected, surely? Otherwise there would be little point in the HDR excercise in the first place. Boom Boom 
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David.
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Photos hosted by Flickr.
www.flickr.com/photos/monobod/
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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Meredith
enthusiast
Reged: 23/10/2006
Posts: 242
Loc: Coventry, UK
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Quote:
Quote:
Quote:
You can't view an HDR image on low dynamic range devices (monitors, projectors, prints) properly as the dynamic range is too high.
What else is there?
If a monitor can display all tones from pure black (255) to pure white (0), what else is there? The camera cannot record anything outside this range, so I am still confused by your statement. HDR is simply a compilation of the best data from both ends, with the detail retained. The limited dynamic range of a camera can either retain highlight detail and block up shadows, or retain shadow detail and burn out the highlights. The monitor can display both extremes, so the combined images display as expected, surely? Otherwise there would be little point in the HDR excercise in the first place. Boom Boom
A monitor can only display each RGB channel in 255 discrete steps - 8 bits per channel, 24 bits overall. An HDR image has 32bits per channel - considerably more detail is possible between the extremes. This is high dynamic range. To view such an image properly you have to compress the dynamic range down to 8bits per channel by tone mapping.
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Meredith Lewis
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Norman
Reged: 23/09/2004
Posts: 1536
Loc: West London, UK
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Er! I think not!
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Regards,
Norman
www.photobox.org.uk
A woman has the last word in any argument.
Anything a man says after that is the start of a new argument.
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Meredith
enthusiast
Reged: 23/10/2006
Posts: 242
Loc: Coventry, UK
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Despite what the the display properties say, monitors can only display 8bits per channel - 24bits overall, unless they are TN LCDs which are only 6bits per channel. Anyway 32 bits overall is a lot less than the 32bits per channel - 96bits overall of an HDR image.
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Meredith Lewis
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Monobod
'Phantom' of the forum!
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In Martin Evening's book 'CS3 for Photogrphers' Chapte 5, there is a well laid out discussion of HDR and the methods used to generate them using merge to HDR in Photoshop, generating a 32 bit image from merged photographs. These are then converted to 8 or 16 bit for editing.
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David.
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datawise
old hand
Reged: 30/05/2006
Posts: 702
Loc: In exile
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As Adesw has already said, tone mapping can be applied to a single image (usually RAW). The tone mapping function is applied after merging several images to create an HDR image, or to a single file in order to bring out extra detail/contrast.
I posted an original/tone mapped single file comparison a while ago which might help show what it does.
http://www.amateurphotographer.co.uk/for...true#Post603964
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Peter Holloway
My Flickr page
Too long in exile...
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Monobod
'Phantom' of the forum!
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Posts: 5672
Loc: Just West of Norwich, Norfolk
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I wonder, can this now be done in the CS3 raw converter, as there is a facility to boost or reduce the colours with a wide range of sliders covering cyans to orange etc.?
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David.
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datawise
old hand
Reged: 30/05/2006
Posts: 702
Loc: In exile
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Funny, I've been trying something similar recently: If (in ACR) you move the Fill Light slider a lot to the right and then bring the Blacks slider beneath it to the right until you get a satisfactory black point you can certainly improve things - I think it's more tone compression than the Photomatix tone mapping details enhancer which seems to be more of a local/micro contrast enhancer.
For me tone mapping in Photomatix is a more complete replacement for multiple masked tone curves adjustments in PS. So long as it isn't taken to extremes it can definitely enhance some images.
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Peter Holloway
My Flickr page
Too long in exile...
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Monobod
'Phantom' of the forum!
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Posts: 5672
Loc: Just West of Norwich, Norfolk
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The problem I have with this is that so many of the photographs simply look unreal. I can understand it if the intention is to create a sureal image, but if it is just to improve the dynamic range, it seems to fail most of the time.
I find I can get satisfactory improvements using just ACR followed by tweaking as a TIFF file in PS CS3.
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David.
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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