Monday, 5 April 2010

HDR - Software Testing

I took some time today to look at HDR and Tone Mapping. Michael Freeman has an interesting section on his website and it seemed the time to have a look at a technique that has become fashionable in recent months. I had looked at HDR a while ago, and used CS3 with absolutely no success. The results were horrible, and as I had no immediate need for the technique I had left it alone. A while ago I had to shoot some hotel room interiors with a massive DR. In that instance I had made 2 exposures, laid one over the other and with a mask and soft brush blended the two as one. The result again was not that good. So, with Landscapes on the agenda, and the possibility of future difficult interiors I returned to the subject.
Photomatix is specialist software for this purpose and seems to offer plenty of control, for "normal" HDR output. I say normal because much of what I have seen in the past has a "painterly" look that cinematographers are using in film making where CGI is involved. All I want is the ability to overcome the constraints of the CCD in my camera. Most CCDs can only see about 4.5 stops of DR. The human eye can adjust itself to see a range of 24 stops.
HDR software uses a number ( say 5 for most situations) of frames of the same image, all with a different exsposure and combines them as one. Typically the bracketed frames will be at -2, -1, 0, +1, +2 stops.
I had taken a few bracketed sequences of Castlerigg Stone Circle, but only 3, -1, 0, +1

This image is my first attempt and in monochrome.

Notes for future work:-

  1. Use the 5 shot auto bracket set up from -2 to +2 and shoot on high speed multi frame setting. If not, as the clouds move there are issues with registering the images.
  2. Always use A priority so that shutter speed is varied and not f stop. This ensures constant depth of field and in focus elements are easier to register.
  3. Always use the tripod.
  4. Continue to use the ND graduated filters as these will help the highlights.
The watermarks are due to it being a trial version

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