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Friday, June 1, 2007

Close-Up Sharpness

The Truth Is In The Details • Make It A Hard Drive • Times Two • When To Use IS • Airports And Cameras • Res It Up

When To Use IS

I do quite a lot of backcountry photography in New Zealand, where, for weight reasons, it’s practical to take a monopod, but not a tripod. I use the Canon 100-400mm IS lens. Is it best to have the image stabilizer mode set to 1 or 2 when the lens is being used on a monopod, or should I have IS turned off? I realize it’s best to have IS turned off when on a tripod.
C. Bycroft
Via the Internet

A monopod definitely improves the results you get with your 100-400mm lens, and Image Stabilization will add a measure of insurance for those sharp images. When the camera is locked down on a tripod, you should turn off the IS because it may cause blur in long exposures with the 100-400mm IS lens. The newer super-telephoto IS lenses actually can use IS when on a tripod by switching to a shorter frequency of movement, and for a long exposure, they give almost the same motion dampening as locking up the mirror.

The monopod, even with a steady hand, has just enough movement to enable the IS to work for you. Typically, you aren’t going to be using the monopod for long exposures. As far as which mode to use, either will work. IS mode 1 is for still subjects, and IS mode 2 is for panning.

Airports And Cameras
I recently went digital with the purchase of a digital SLR. As I was reading the manual, it stated not to expose the camera to extreme electromagnetic radiation. Is there any concern regarding airport security X-ray machines and the radiation they emit damaging my D-SLR or any other equipment?
V. La Polla
Santa Fe, New Mexico

There’s no chance of radiation damaging your camera or your media in the airport security machinery. The problem with extreme electromagnetic radiation arises when you actually photograph in its presence. It can cause noise or banding in your images. This problem would be much more likely to occur in a medical facility next to powerful MRI machines, for example, than in the airport security area.

While researching this question, I learned something new. Many external battery packs contain a transformer that ramps up the voltage for flashes or the camera. Theses power packs can create a pretty strong electromagnetic field that shouldn’t be in close proximity to your storage media while files are being written. It’s better to leave the battery packs attached to your belt, away from the camera, than to attach them to the camera. Auxiliary battery grips made by the camera manufacturers aren’t a problem.


Res It Up
At the Photo Marketing Association show in Las Vegas, I saw your large panoramic photo of shorebirds on a log. I was wondering how you were able to get such a high-resolution print, considering the size. Besides the fact that this is a composite of five exposures, did you upscale the image or use any special RIP processing prior to printing?
D. Rice
Via the Internet

Yes, the "birds on a log" image is a composite of five exposures from an 11-megapixel camera. Each image from this camera is capable of at least a 20x30-inch print, and I often make 40x60s. Yes, this flies in the face of conventional wisdom that says you should never enlarge an image beyond the resolution of its capture. In that event, my 11-megapixel camera would be limited to roughly 11x14-inch prints at 300 ppi.

But, as you could see from the print in Las Vegas, even very large prints can retain excellent resolution. Don’t be afraid to interpolate! Interpolation actually expands the distance between the pixels in an image and fills in the blanks with information derived from surrounding pixels. This sounds scary, but there are some software programs that do an excellent job: Adobe Photoshop, onOne Software’s Genuine Fractals and Alien Skin BlowUp, to name a few.

You’ll know that you’ve enlarged beyond the capability of the image when you’ve lost the sharpness and detail that define a fine print. But step back a bit to make the judgment, perhaps four to five feet from a 16x20 print. We tend to view digital prints from a closer range than we did with darkroom prints because there’s considerably more detail to be seen in them. An optimal viewing distance is one that comfortably allows the viewer to appreciate the print’s quality as well as its message.

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