To get my HDR result, I first needed to take three photos of the site I wanted. I selected the intersection of 14th and I streets in NW DC to get the best mix of a well-travelled one-way street, a well-traveled two-way street, trees, and a tall building. Two of these images were generally metered to the intersection (slight accidental exposure difference), and one to the sky.
I didn’t do the “single-metered, -3EV, +3EV” thing, because I imagined the result to have visible, transparent, and crisscrossing cars, and that wouldn’t come with the traditional method of HDR bracketing. (I wanted the transparency in the final result even before I reached the site.) After loading the images onto the computer, then I had to merge them.
I tried Photomatix Pro, but of course I got the watermark BS. Fortunately, there’s a more basic Photomatix program that doesn’t have the tone mapping or use the watermark. So, I downloaded the program, and merged all three images with the combination of the Highlights & Shadows tool (with one of the light images and the dark one), and the Average tool (with the combined/saved image as well as the remaining light image), both from the “Command” menu of the program. Then I saved the result as a TIFF.
(I have the impression there’s a way to do the Average function in GIMP, but I haven’t found it.)
Now this creates a pretty good image, but at least with this photo, the top right of the photo doesn’t reflect the cloud cover that’s there. So, outside of all this action, I created a second rendering, this time with GIMP and the free HDR tool, and applied many steps that I’m not sure would work on every photo, so I won’t list them here. It really is all about trial and error, and a lot of time and patience.
As you can see, the top right windows are good, now. However, the taxi doesn’t provide much transparency, and the bus is very dull, among other side effects. So, I simply took these two results, opened them into Photomatix, placed them through the “Average” tool, then saved the result as a TIFF. Here it is (after a basic curves adjustment, some slight colorization, et al, in GIMP):