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| Photo by Jack Howard |
| With some advanced image-editing techniques, it's possible to completely erase moving objects from your high dynamic range photos. Click photo to launch step-by-step tutorial. |
In the field:
1) Use a tripod. Even the slightest movement of the camera between exposures will be noticeable.
2) You can autobracket if you want, but make it in the biggest EV increment your camera allows.
3) If you want more than three source images, choose your aperture and ISO speed, and keep these locked. Change your shutter speed in full-stop increments from a virtually black frame to an almost completely white frame.
4) Moving objects will be "ghosted" in the Merged/Tonemapped HDR. Still subjects work best. Make sure there are not cars, pedestrians, etc., moving in between exposures.
5) Dramatic differences in colors and "textures" seem to work well in HDR. Choose subjects that have good color differences, and good contrast between natural and/or manmade textures
6) For very long exposures past 1/15 sec, consider using Mirror Lock-up if your camera offers it, to minimize camera vibration during the exposure.
In the Digital Darkroom:
1) These processes can take a long time, even on a new, fast computer. Consider doing some tests and experimentation on small, screen-sized images first, to get a feel for HDR. Your scratch disk will thank you.
2) Don't panic when you first do a merge to HDR and see the weird, thresholdy HDR "Neg." It has to be tonemapped and adjusted before it looks OK. You're only halfway there so far.
3) Be patient when making Tonemapping adjustments, especially on a print-sized image. Let the preview update itself before making another adjustment (did I mention that these are big, slow processes?)
4) You can cheat a bracketing sequence of one image by playing with exposure controls to make a series to merge to HDR; but this does not work with RAW files in Bridge, using Bridge/Photoshop to merge to HDR, because the program is crunching the RAW information, and even if you apply exposure changes to import to Photoshop, the RAW info remains the same. Convert the RAW files to 16-bit TIFFs and this should work.
5) Experiment! Use different settings and curve controls to see what each adjustment does to your image. Since the Tonemapping process outputs a non-HDR file, you can go back to your HDR "negative" and apply different settings and save your results without affecting your HDR "negative," provided you save a copy of your HDR-format image prior to Tonemapping.
6) There's no real "formula" or specific set of numbers that will work for every HDR image. The numbers and curves I've used for one image don't necessarily work for a similar image. You've just got to play with it.
7) Make sure you've got a fair amount of free hard-drive space to save HDR-format files. A full-size HDR "negative" file from 4 Canon 5D RAW images yielded a 145.6 MB HDR image!
8) Try before you buy! Give Photomatix and Photoshop CS2 a test run with their free demos. If you get a result you like, save the settings, and you can go back and reapply the setting to your source HDR image after you've purchased a license for the software.
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