HDR - High Dynamic Range

Dynamic range was not a term that was often used in film days for those subjects which had a subject brightness range in f/stops grater than could be squeezed onto film, especially the six or so stop range of color transparency films. But digital has introduced a relatively easier fix for taking effective photographs of a cityscape at night, the interior of an old European cathedral or in a rain forest. So now it is a bit of a rage, if it can be done, so let's all do it! I received a review copy of a book by Jack Howard titled PRACTICAL HDRI that should have been encouraging, and decided not to review it. Besides covering only Photoshop HDR and a few 3rd party odd-ball solutions, the results printed in the book would inspire me only to say why would I want to do this.

It seems like an eternity ago when I was on staff at Petersen's PhotoGraphic located in Hollywood and only motivated to take photos of the city at night because it was so ugly during the day. And of all extremely long brightness range subjects the city at night can measure usually at least 10 to 12 f-stops from shadow to highlight excluding the light sources themselves. There were solutions to this challenge with film before Photoshop, which I employed and wrote about in Petersen's PhotoGraphic for both black and white and color. But there really was not much interest, as they were difficult to use, but not much more so to get good results than the HDR utility Adobe put into Photoshop some time back. However the challenge was largely the same. How do you get a good image on a print when the range of the subject is so great when compressed to what will reproduce photographically that the image has so little internal contrast and tone separation so it looks flat!!!!

With black and white film many of us used some regimen of exposure and development like The Zone System to control subject contrast relative to the range of densities that could be printed. But ten or twelve f/stop range subjects were beyond even that. So the newest technique in the 80's was to use an extended range developer like what was made by Kodak for developing Tech Pan high contrast copy film to get normal contrast negatives of average scenes with super fine grain as well as superb sharpness in 35mm B&W photographs. This developer was formulated originally by the military for tactical photographic surveillance and consisted almost entirely of Phenidone and Sodium Sulfite, but without some added tweaking was even too soft a working developer. But used with a more standard fast B&W film like Kodak Tri-X with its film speed lowered by a factor of about 10X or more you could obtain a negative of a 10 plus f/stop cityscape at night and print it in #2 paper and get detail in the deepest shadows and the brightest highlights.

In the film days, long subject brightness range color was a bit more difficult with transparency films, but there was an option. Duplicating color reversal film in 35mm, 70mm and sheet sizes had a much lower inherent contrast response, to counter the contrast multiplication copying a color film image onto another reversal color film involved. But duplicating color transparency films were both very slow, balanced to a tungsten light source, and varied in color response from one emulsion batch to another. This meant a lot of filtration adjustment to achieve an acceptable color response in the result, including converting from a tungsten color temperature balance to daylight and Color Correction filtration to compensate for the peculiarities of each emulsion batch of film used. So pre-testing was required and then your stock of film had to be refrigerated to keep it the same over any period of storage time. But with this done, as long as you could deal with an effective film speed usually well below ISO 10 you could obtain good transparency results with extreme contrast subjects of many kinds, as long as they were stationary.

With digital the HDR solution is dependent on being able to make a set of exposure bracketed frames in Raw format with the camera on a tripod so the frames will register when layered and blended together. That the basics that were supported by the Photoshop HDR utility, which supports putting up to five bracketed frames together to make one photograph that has detail across a wide subject brightness range, like the kinds of subjects I mentioned above. First of al,l some experimenting is necessary to get the range of different exposures needed that will provide a blended image with good photo qualities. And the old bugaboo that when you compress a 10 or 12 f/stop range into a single image that is printed, the separation between the tones is decreased markedly and the image can look flat, and there may be insufficient tone differences in the print separating different parts of a subject that in reality were well distinguished in tone and brightness.

The failure of the Photoshop HDR utility is there is not a good method incorporated to optimize the image characteristic curve to enhance areas of internal contrast and tone separation. Maybe some of the third party utilities Jack Howard described in Practical HDRI, function better but I did not read anything that was encouraging, and his results were not convincing.

However for anyone who can run Microsoft Windows applications, the Corel PaintShop Pro X2 version I tested and reviewed not long ago in Shutterbug has an HDR utility that has an optimization function and it is a much simpler and easier utility to use than the Photoshop version, maybe because Adobe was first with an HDR solution and those that have followed have learned from that.

The bottom line is HDR, especially for landscape and architecture photographers and those who like to shoot nighttime scenes in the city, PaintShop Pro X2 is an under $100 solution that works well enough for any enthusiast, and the cost of effort and learning is also modest to obtain advantaged photographic results from photographing subjects with a much greater subject brightness range than any digital camera can capture in a single exposure.

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