Here is a brief note about using the probably often overlooked HDR tools in CS5, including the 32bit color picker and the 32 bit Exposure viewing tool.
Here is Adobe's help page regarding the color picker:
http://help.adobe.com …3-B2ED-8FB8FF67E8BDa.html
What is cool about the 32 bit color picker is the ability to choose a color and an intensity of that color, in exposure stops.
With that in mind, I experimented with devising a scale in CS5 that would help me visualize the tonal range in a 32 bit image, and how that range is compressed or tone mapped during HDR toning and conversion to 16 bit. Some HDR applications have 32 bit histograms that display the 32bit data in terms of EV or similar scale. CS5 has got nothing like that.
So, I used the 32 bit color picker to make a couple of scales in my 32 bit image, one scale ranging from -20 stops to +20 stops in two stop increments, and another ranging from -10 stops to 10 stops in one stop increments (finer resolution). For each scale I created a vector square and used the 32 bit color picker to specify a 50% brightness at each particular intensity (stop). That is, each gray square is 50% gray at that particular exposure. To get a little more feedback, I made the labels a half or full stop lighter or darker than the square they were labeling, giving a finer resolution to the exposure scale. Here's what I got - note that this is a screen shot of CS5 rendering a 32 bit image:
Note that my display cannot display the full range of the image or the scales. In order to "see" the clipped data, we need to use the 32 bit exposure slider. I can use the 32 bit exposure slider to bring various portions of the full dynamic range data into view on my non-HDR display, and the scales I devised will respond as well , giving me an idea of where the various values in the scene fall in terms of exposure in the 32 bit file, and what portion (range) of the data I am viewing.
Here is the highlight value example:
and here is the shadow value example:
In both cases I am examining the tones in the image and using the scale to identify the exposure of those tones - this gives me a rough approximation of the dynamic range of the scene as well and helps me to strategize a tone mapping solution.
Here is the default CS5 tone mapping that occurs when I simply select HDR Toning form the Adjustments menu, with the Local Adaptation tone mapper:
BLAH! If you ever wondered why that kind of image is awful, color aside, look at how the 10 stop scale has pretty much been flattened into an almost constant gray mess - no global contrast at all, and a disgusting mess of local edge contrast. In all likelihood the default values that created this mess result from the fact that I have artificially given the HDR scene 40 stops of dynamic range to deal with. What would be cool is an action or script that would permit the user to enter the min and max exposure (stops or EV) and the exposure increment and have the script automagically generate the scale - in fact, it would even be more super awesome if the script determined the min and max exposure and created a scale all by itself!
Hello programmers.... Anyway, I digress. (I think that Guillermo's ZeroNoise does generate these scales automatically, the user choosing from the Adams Zone scale or a 16 EV exposure scale - see, I knew someone already figured this stuff out).
Using curves will help reestablish contrast, and using gamma and exposure will help with anchoring white point and mid tones as well. See:
Now the scales are back to something respectable, although the 32bit preview still makes them appear whacked out sometimes, so squint a little when viewing them
.Now you can convert to 16 bit and get the image into shape. Here is the 16 bit image, ready for finishing - because I did the toning already in 32 bit, the conversion to 16 bit was a straight exposure of 0 and gamma of 1 (i.e., no adjustment - Image > Mode > 16 bit > Exposure and Gamma).
The image gets smushed into LDR land, and needs some rehab, but the scales look respectable - the black point needs some work, for example.
Note that this is an EXTREME example - this was shot in a dark warehouse with bright sunlight outside trying to illuminate the warehouse and failing miserably. The scene is in excess of 16 stops of DR.
Why is all of this remotely useful? Because you can experiment with the scales in 32 bit land to determine how your edits translate for output to LDR media (display, print, etc.). You can figure out what kind of clipping points and dynamic range compression you need to establish good tonal reproduction on your output device of choice. Once you have toned your image with the scales, you can save your toning adjustments as a preset and apply the preset to the same HDR data without the ugly scales in the way. Hopefully it will make you think about HDR image acquisition and processing in terms of OUTPUT to LDR devices, and give you a solid foundation for making decisions about image acquisition in terms of output for a given device.
Hopefully you will find the 32 bit color picker and the 32 bit exposure viewer/slider helpful - don't overlook these powerful tools!
Have fun,
kirk
