Q. I want to take HDR images using my Nikon D3100. Any tips on how to do this?
- Use manual focus (you can use auto focus then switch to manual focus to lock your focus). You don't want the camera refocusing on every shot.
- Use a fixed aperture. If you change the aperture, you will change the depth of field which means your images won't stack up properly.
- Set your ISO to a fixed value. Be sure auto ISO is turned off.
- Purists will shoot in raw and convert to linear light space TIFF, but when playing around you can shoot in JPEG and still get decent results.
- Take a series of shots changing only the shutter speed. You want to have shots properly exposed for the dark through bright areas. Don't go much more than 1 stop between images. You can do 2 stops, but the results aren't as nice as 1 stop. Use your histogram and/or highlight review mode to see what your exposure looks like on your camera. The highlight review mode is very useful as it shows which objects are overexposed. Some folks will try use the bracketing feature, but that will work only some of the time.
- If you use raw, purists will convert the image to a linear light space TIFF image. It will look horrible since the gamma is set to unity. However, mathematically, it is easier for HDR programs to swallow a linear light space. Such a program to convert to linear light space TIFF is dcraw.exe .
- Purists will align their image stack due to slight camera movement on the tripod. There's a nice program called align_image_stack.exe which is included with Hugin. This program will correct small camera movement.
- Finally, you do your image stacking. There are a number of programs to do this. Newer version of Photoshop does a nice job with HDR. If you want to go free, then enfuse.exe (part of the Hugin distribution) or TuFuse.exe. These are command line programs which give realistic final images. There are GUI wrappers for these programs. If you want strange tone mapping colors, then use QtPfsGui or similar ilk which give surrealistic colors (some like it because it's arty, I think it looks goofy).
- If you went the purist route and used linear light space, then you need to add a gamma of around 2.2 to your images. You'll probably want to play with the levels curves to beautify your images. You'll need Photoshop or GIMP to do this.
