Sunday, March 30, 2008

high dynamic range images

High Dynamic Range imaging (HDRi) is often called the process of combining bracketed images with different exposures and subsequently tone-mapping the resulting image to give a high and exaggerated dynamic range with more details on the highlights, shadows and midtones.

When doing HDRi, I use the trial version of Dynamic Photo HDR from Media Chance and it is a better software, for my requirements, than what the Adobe CS3 can offer.

Your very first concern when processing images in HDR is to get at least three (3) images with different exposures. The more images of the same scene is of course better so that you can set the EV value increment to a narrower figure. Getting a series of the same scene would require you to set up a stable and sturdy tripod where you will mount your camera. Fortunately for me, I am using a Nikon D200 where it can take a series of shots up to nine (9) frames. Other Nikon DSLR models like the D80 and lower models can only take three (3) frames. Doing this would again necessitate to set the camera to a Continuous Shooting Mode and triggering the shutter release button thru the built-in timer function or with a cable release gadget you attach to the camera to prevent any camera shake from affecting the frames of images you will need to combine when doing HDRi.

Now, assuming you already have at least three (3) images to process with, load this image using Dynamic Photo HDR. For a quality compromise, it's better to have at least five (5) images of the same scene to work with.When these images with bracketed exposures were already loaded, the next thing to do is to check whether these images are properly aligned. You can align them automatically or manually but I'd rather do manual alignment and rely on my sense of sight's judgment. You can tweak the merged images with advanced options like pin warping and anti-ghosting options but that is for the advanced users.

After you've finished the alignment process, you're now ready to tone map the exported HDR image. With Dynamic Photo HDR software, you have six (6) tone mapping options: Eye-Catching, Ultra Contrast, Smooth Compressor, Auto-Adaptive, Photographic and Human Eye. Ocassionally, I always get better images for my taste whenever I process the HDRi on the Eye-Catching mode but I also have great results using the Ultra Contrast mode. When you want subtle results or less-than the hyper realistic HDR effect, you can either process your HDRi using the other options mentioned above.

In the examples given, the 3rd and 4th photos from top were both processed in Ultra Contrast mode while the rest of the images were all process in Eye Catching mode.