Merge to HDR using After Effects

[Carl Larsen]

Photoshop and photomatix really are the best tools for creating high dynamic range images – either for a 32 bit finish, or for tome mapping back to 8 an 8bit color space. Is there a specific reason you don’t want to do it in one of these two apps? Photomatix pro has some great automation features.

[Chris Dortch]

I need to output 32 bit, not an 8 or 16 bit tone mapped. I know that Photoshop and Photomatix can create a 32 bit file, but If I knew the science behind properly combining images to boost exposure range, I could solve this particular problem which permits me from using either of these programs. What does Photoshop (and Photomatix) actually do to the 3 images to create a single 32 bit image?

[Carl Larsen]

The basic principle behind HDR is that you shoot a variety of images with different exposures (typically 0ev, -2ev, +2ev) and combine them into one image for an increased dynamic range.

In their simplest form, these apps look at the luminance of the 0ev image and add information from the under exposed image to the clipped areas of the original (using a threshold matte), and add detail from the overexposed image into the darkest portions of the original (using a threshold matte).

As for creating an HDR sequence in AE, I’d still encourage you to try an automated approach using another application and then dealing with the image sequence in AE. My results weren’t pretty.

But, that’s just my .02.

[Chris Dortch]

Thanks for the info Carl. I too usually use the automated features of another application (Photomatix) to produce a sequence of EXR’s. I have found a situation where this will not be the best approach however. Is it possible to use a combination of blend modes and maybe certain effects inside of After Effects to create an HDR that matches the color information of an HDR created using Photoshop or Photomatix? Or is there a place someone can direct me to that might shed some light on the subject. I think the info about luminance combination using a threshold matte is very interesting and is close to what I am looking for.

[Carl Larsen]

So after more playing around with some of my own bracketed shots, it appears that the best solution I can generate at this time is also the simplest.

Drag your bracketed images into a new comp in AE, set it to 32 bit, and stack your images from darkest to lightest. (that’s darkest as layer 1, lightest as layer 3) Next, change the composite mode to add.

Although it does not give me quite as much dynamic range compared to when I combine the same images using the merge to HDR function, this method does yield superbirght values and realistic light characteristics which I found to be generally acceptable. You’ll have to play with it yourself to determine if this method will work for your specific situation.

You can play with the exposure slider at the bottom of your comp window to see how the superbright values sit in the comp.

[Chris Dortch]

Thanks for looking into that. I came up with a similar solution; however, the layer order you suggested improved the result of my tests. Thanks again. I will continue to experiment to see how I might get that extra range. Now if I could only get Adobe’s secret HDR recipe…

[Chris Wright]

to get extra range, just take more picture of varying exposure, like 5 instead of only 3. It works great!