any recommendations on good GND filters?

[Bob Atkins]

There's also Luminance HDR (which used to go by the name Qtpfsgui). Just by the old name you can tell this is an open source project!

Photomatix used to have a free version, but I don't think they do anymore. It was called "Photomatix Basic". I have it installed on my PC and you might be able to still find the installation program still floating around on the web somewhere. Just Google the name and see what shows up.

[emanresu]

cool. this list is super!  so now, the question is what exactly is the difference between HDR and tone mapping?  because some of the "HDR" tools do tone mapping, and my first thought is HDR is like using GND and ND filters to compress the dynamic range of the scenes, but tune mapping is what lead to many cartoon-ish (and aweful looking) pix on the Internet... is this correct?

[Bob Atkins]

I think Tone mapping is what you have to do to display a true HDR image via a medium with a smaller dynamic range. The image itself may contain information in areas which differ in brightness by a factor of 1 million, but if the display device can only show differences in brightness by a factor of 1000 you have to modify the tone mapping of the image in an attempt to show the detail in both the bright and dark parts of the image. If you don't then you'll just get a small part of the brightness range displayed along with either blown out highligh detail or no shadow detail (or both).

If the dynamic range of the image is too large and/or you use a tone map that's stronger than you really need, then you get the HDR cartoon look.

[emanresu]

would it help if one day the technology for display goes beyond 8 bits per channel?  I think part of the reason why digital photography suffers from dynamic range issue is because we only have 256 values for each channel, so for any intensity in an individual channel, it has to be displayed using one of 256 values.  But if we can add a few more bits to each channel, then we will have 256 * 2 ^ <num of additional bits> to accommodate more ranges.  Of course, at the same time, the physical technology has to evolve as well so on a typical monitor, it can display something much more intense for each channel (and burn our eye sockets out).  not sure about printing though.

[KeithB]

This says that a good LCD monitor has 10 bits of dynamic range (How handy that a stop is a bit!)  And the human eye 10-14, so a good monitor can do pretty good.  Raw files, of course have 14 bits or so of dynamic range.

The question is whether the pipe sending the data to the monitor is 8 or more bits.

[Bob Atkins]

Of course that 10 bit display would only be 10 bits in a darkened room with the monitor set up properly. Turn the room lights on and you lose the shadows.

What really counts iis the dynamic range of prints, since a print is how most photographs are eventually displayed. I think a print probably has about a 6 bit dynamic range.

Whatever the dynamic range of the captured image, it has to be tonemapped down to about 6 bits to be printed. You can still represent the whole dynamic range of the original but it probably won't look very natural though if you're compressing 20 bits of HDR onto 6 bit paper.