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Wednesday, November 1, 2006

Photographers In Harm's Way


How Far To Go For The Ultimate Photograph? • Reciprocity Compared • Digital Black-And-White • Snowy Details


Reciprocity Compared

Q) How would you compare the aspects of reciprocity failure in long exposures on film versus digital SLRs? My first forays into digital long exposures have given me poor results.
G. Thompson
Hartford, Connecticut


A) In long exposures on film, there's a noticeable loss of image quality due to reciprocity failure, which is revealed in color shift, excessive grain in underexposed areas of the image and an unexpected lengthening of the exposure due to the inability of the layers of silver to record the information efficiently.

From the beginning, digital cameras corrected the color shift and controlled the exposure time, but long exposures on the early D-SLRs generated a lot of noise—tiny, misplaced artifacts of color in the darker areas that resemble the grainy look caused by reciprocity failure in film. In a digital camera with a large number of pixels packed onto a very small sensor, the opportunity for misplacement increases dramatically. But with the latest processing and chip technology, including larger sensors with bigger pixels, noise is greatly reduced in digital long exposures. Couple the camera technology with noise-suppression software in our computers, and the end result is that digital long exposures represent a huge improvement over film. It's still not perfect. Underexposed areas in very long exposures (more than 30 seconds) still show some noise. But the results get better with each new generation of D-SLR, and even the digital point-and-shoots are offering more creative possibilities with long exposures and higher ISOs.

Digital Black-And-White
Q) I'm seeing some beautiful black-and-white images in magazines and exhibitions lately, and I know the photographers are shooting with digital cameras. How would you advise dedicated black-and-white film photographers to fulfill their visions in digital format?
C. Medina
Riverside, California


A)
Some point-and-shoots offer a black-and-white mode through the camera's software, but these aren't going to yield the quality results you're seeking. Most professional-level digital SLRs shoot color only; black-and-white renditions are achieved after capture with imaging software. Keep in mind that, as in any other quality image, the digital capture requires good exposure, good contrast and sharpness, whether the final print will be rendered in black-and-white or full color.

To maintain a full range of tones in the imaging process, most knowledgeable digital photographers use a channel mixer adjustment layer set to monochrome, where the percentages of red, green and blue color can be manipulated to give the desired effect, as if you had used filters at capture. Once you've converted the image to black-and-white, you can make precise adjustments within the imaging software to attain the kinds of effects you used to work for in the darkroom. But you can achieve much greater precision with skilled use of imaging software than was possible with burn and dodge, and who needs the chemicals?

Finally, you can finish your black-and-white image with any number of excellent printers and a wide variety of papers and other media. Epson's 2400, 4800, 7800 and 9800 printers use eight pigment inks, three of which are blacks. Canon's new iPF5000 and iPF9000 also offer three black inks, as well as eight additional pigment inks, yielding a wider color gamut that gives excellent tonal range in black-and-white prints, coupled with easy and efficient switching of inks for top performance on glossy and matte papers.

For the ultimate tonal range in black-and-white photography, try a professional D-SLR converted to receive only infrared light. In infrared landscapes, skies go dark, foliage goes white and clouds are brilliant. For portraits, skin tones are softened and eyes are exceptionally clear. To find sources of IR cameras or to have one of your digital camera bodies converted to IR, do a Web search on digital IR.

Snowy Details
Q) Now that you've moved to Colorado, what advice can you give about proper exposure for photographing snowy landscapes? My snow pictures tend to be either washed out or dingy gray.
B. Smith
Telluride, Colorado


A)
With either digital or film capture, first take an exposure reading off an area of bright snow. But wait! If you use that reading, you'll get gray snow because every exposure-metering system wants to convert the metered area to a middle tone. The answer is to open up from the metered reading by one to one-and-a-half stops, then lock that exposure into the camera's manual mode. The end result is a white snow, with detail. Your experience will tell you how far to go with the increased exposure. The locking of the exposure in manual is necessary because you might have darker objects in the frame and auto-exposure will take that into consideration and skew your snow-oriented reading back into overexposure.

If you're working in digital, after capture, check the histogram on the LCD, which graphs the tonal ranges of the pixels in your image. If your graph piles up the pixels against the right side, you're overexposed and there will be no detail in the snow.

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