Tone mapping...what does it do?

[slackercruster]

What does tone mapping actually do?

Does anyone have a 'before and after' photo to show tone mapping in action?

Thanks

[polyglot]

Tone-mapping is basically automated dodge-and-burn. It analyses the image in order to decide which bits to make brighter and which to make darker; the net effect is reduced total dynamic range without a reduction in local contrast.

Before & After is a little difficult to show because by definition, the Before image probably has more dynamic range (e.g. 12+ stops) than any affordable display device you might have access to (paper is about 5-6 stops, LCD/CRT monitors maybe 8, OLED and some plasmas can go slightly higher). You could render the Before at reduced contrast, but that's not really a good representation.

[Valdecus]

Tone mapping is the process of mapping a tonal value to another tonal value. The resulting image may have the same dynamic range, a reduced, or an increased dynamic range.

In the context of HDR photography, tone mapping algorithms are used to reduce the dynamic range of an HDR image in order to be able to display the image on screen, or print it to substrates that have a lower dynamic range.

Note that any change of tonal values actually is "tone mapping", for example applying a simple s-curve or moving th contrast slider in Lightroom.

Cheers,
Andreas

[Old-N-Feeble]

Hmm... interesting.

Anyone willing to show a high DR image retaining proper shadow detail while blowing out highlights... plus the same image with retained highlights but blocked shadows... plus a final image with tone mapping??

[D. Bryant]

Hmm... interesting.

Anyone willing to show a high DR image retaining proper shadow detail while blowing out highlights... plus the same image with retained highlights but blocked shadows... plus a final image with tone mapping??

Ever hear of Google? Mega tons of examples on the net.

[Valdecus]

Christian Bloch's website 'HDR Labs' has some nice examples to show the results of different tone mapping settings in the context of HDR image processing:
http://www.hdrlabs.com/gallery/realhdr/

Cheers,
Andreas

[slackercruster]

Thanks for all the replies!

So, tone mapping is all automated? It is not done by our input, the computer is the one that decides?

[Michael Rosenberg]

Look at Charles Cramer tech tip on Luminous Landscape for a tutorial on a type of tone mapping done manually.
Mike

[cjbroadbent]

Thanks for all the replies!

So, tone mapping is all automated? It is not done by our input, the computer is the one that decides?

Not at all. I can explain what I do with tone-mapping. I take a lot of trouble lighting and developing for a negative that has range of tones that would fit reasonably onto a medium contrast bromide paper. My scanner seems to be able to retain the end values, but the mid-tones are pretty flat and no amount of curve tweaking can breath true life into them.
So, in addition to the vanilla scan, I do two extra scans, one concentrated on highlight detail and the other concentrated on shadow detail. In Photomatix (photoshop can do it too, but with less delicacy), I merge the three scans and tone-map.
All the computer does is to MASK HIGHLIGHTS, SHADOWS AND MIDTONES so that you can blend in the better parts of each. There is nothing automatic about the procedure apart from feathering the masks. It is just as though you were doing the job under the enlarger with a burner or a dodger. Done with restraint, you get a file that looks like your original negative with no fuss. Tone-mapping is for descriptive, rather than expressive, manipulation.
Recently, I've done a lot of still-life with white flowers and deep shadows. These are 8x10s
73943
73944

[polyglot]

Thanks for all the replies!

So, tone mapping is all automated? It is not done by our input, the computer is the one that decides?

Depends on the software you use. Generally they have a range of adjustability from "full auto" to "tweak ALL the parameters", not to mention there are many tens of different automated algorithms for tonemapping; they all work and look different.

I strongly suggest you go get a demo version of something like Photomatix (note it's not "Photomatrix") and give it a go. Trying it will give you way more info than a bunch of noodling on a forum.

[Peter Mounier]

Here's a simple method that you can try if you're just trying to get more shadow/highlight detail (or contrast) out of your scans using Photoshop, and curves alone aren't doing it. I'll first say that Aperture (and presumably Lightroom) work faster and better. But if you don't have one of those apps (or one of the others suggested), this works fairly well.

Open your document in Photoshop and have your Layers, and Channels windows open, with the Channels window visible.
Hold down the Shift and Command keys then click on the RGB Channel. That action selects the pixels in the highlight range of the image. If I understand it correctly, you have selected all of the pixels with an rgb value of 128 higher.
* If you click it again (still holding the shift/command keys) you'll add to the selection the next 50% of the upper range of remaining pixels. Repeat as necessary.
* You can invert the selection to automatically have the lower range of pixels (shadows) mapped.
* Map the lower range of pixels as described, and create a layer/shadow mask. Then make a new layer of just the highlight range, as described above. Select the shadow mask, then add to the selection, the selection of the highlight mask. If you're still with me, you now have a selection that includes the shadows and highlights, but doesn't include the midrange. Invert that selection to create a midrange layer/mask.
Now you're free to make adjustments to each of the three tonal ranges.

Peter

[slackercruster]

Thanks for the rundown Peter!

[Henry Larson]

Here is an example
First is jpg second is tonemapped
Chiricahua National Monument Southern Arizona
I am having a problem uploading the Tonemapped image
74191

[Henry Larson]

74192
Here is a second try at the tonemapped image.
I hope this helps