tone mapping ?

[tonyjr]

What is tone mapping ? I'm just starting to play with HDR - still reading about right now .

[David]

Hi Tonyjr - The idea of tone-mapping is quite simple, but in practice there is great complexity. When you create an HDR image, the range of "tones", i.e. the total dynamic range of the image is many orders of magnitude greater than that which can be displayed by a monitor or printer or your camera. In addition, the HDR file is normally stored as a series of floating point numbers, not integers. Thus, tone-mapping is the mathematical procedure (algorithm) whereby this large dynamic range of floating point numbers is brought back to integers (and hence pixel values) that can be displayed.

Let me give a very simplistic example. Suppose you normal exposure involves the numbers 1 to 100 as integers, but your HDR file contains a thousand numbers anywhere between 1.0000 to 9999.9999. Then the tone-mapping procedure will convert these latter numbers back to the integer scale of 1 - 100.

Unfortunately(?) for the photographer who wants to use HDR imaging, there are a large number of algorithms that can be applied. Some of these are based on how scientists believe the eye functions, some on more strictly colorometric ideas. However, commercial software such as PhotoMatix you have a very restricted choice as to which tone-mapping option to use (basically one or two). Even so, there are various parameters that you can adjust to give the desired result. In software such as "Qtpfsgui", which is free open source software, there is a bewildering array of tone-mapping options, along with associated adjustments. Thus, stick to a simple system such as Photomatix to start with.

I hope this helps.

David

[tonyjr]

Thanks --
That's , kind of helps .
1st - I'm on a Mac .
2nd - I have PS CS3 extended .
3rd - I have a Canon XTI
4TH - About 7-8 lens , tripod , bellows [ coming ] 2 different remote timers .
5th - I had my eye operated on last week - No lifting , bending straining - etc .
6th - When I can set up my first HDR will either be my house or a flower .
7nd - came across HDR while researching DOF for flowers , bugs.
I am on / in reading stage of HDR right now .
I don't just jump in . In terms of a car , I want to know how to turn on heater , lights , adjust the seat before I start the car .
Any adive is welcome - good books , web sites methods , etc
Thanks again .

[David]

Hi Tonyjr - try this site for a reasonable overall explanation of HDR.

http://range.wordpress.com/2006/07/1...ng-relaxation/

I don't have the Photoshop CS software, thus I can't help immediately with what the parameters are in that bundle. Let me know and I'll try to interpret them.

David

[tonyjr]

Thanks , that's a lot of reading . Will start reading , probably tonight .

[David]

Tonyjr - re info about HDR see the recent post by F-Art - he has found an excellent tutorial.

David

[tonyjr]

Thank you - helped some more . Will read a few more times . I ordered the book Practical HDRI
I'm about 1/3 way thru the other one suggested .

[tonyjr]

Book came today - Practical HDRI - still reading other one , but at least this one has and index .