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Tuesday, July 7, 2009

The Perfect Solar Storm


Chasing The Aurora • The Full-Frame Advantage • The Silent Click • Please, Release Me

Labels: How-ToColumnTech Tips


This Article Features Photo Zoom
tech-tips This is the wallpaper image included in Microsoft Vista OS. If you’re running Vista, you can use it as wallpaper on your monitor. The image was taken with a Mamiya 645 on Kodak E100S slide film in approximately 1999. The image is available through www.gettyimages.com.

Chasing The Aurora
Q I saw your photograph of the looping aurora borealis as one of the wallpapers within Microsoft Vista OS. Where did you take that photograph, and what’s the best time of year to try to capture the aurora?
B. Weber
Via the Internet


A The shot you mention was taken in September on Muncho Lake in Northern British Columbia, Canada, located at Mile 462 on the Alaska Highway. The aurora borealis (the northern polar lights) is increasingly evident as you approach the magnetic pole. The easiest place I’ve found to view and photograph the aurora is Fairbanks, Alaska, and a number of tours will help you. (To name two designed just for photographers, see www.alaskaphotographics.com and www.photosafaris.com; these companies use photographer/guides I know and recommend.) Or you can join us at Camp Denali (www.campdenali.com) in Denali National Park and Preserve in fall 2010, where we’ll most likely have the aurora experience right outside our cabins. The best time, of course, is during periods of extended darkness, so for the northern lights that means September-October and March-April, when it’s also really cold. For more information about the auroras at both poles, see a great website from the University of Alaska that even forecasts the best displays (www.gedds.alaska.edu/auroraforecast/).

The Full-Frame Advantage
Q
My issue is with cropped sensors vs. full-frame sensors. Full-frame cameras cost more than those with smaller sensors and, I guess, they’re assumed to take better photos. It seems most professionals use full-frame cameras. But if you have two cameras, one with a cropped sensor, and one with a full-frame sensor, both with the same number of megapixels, shouldn’t the cropped sensor, by logic, have a higher resolution since the same number of pixels are more spread out on the full-frame sensor? When you break it down, wouldn’t there be more pixels per inch on the cropped sensor since it’s the same number of pixels in a smaller space?
N. Gardner
Via the Internet

A Your analysis overlooks a critical variable: All pixels aren’t created equal. The quality rendered by any sensor is a product of the number and size of pixels and the technology in the camera that manages their collection and processing of data (that is, the information that makes up your image). In your example, the pixels on the larger sensor are themselves larger. The advantage to this is that each pixel gathers more light, improving the overall image quality in terms of color and detail. Furthermore, larger pixels improve capture at higher ISOs by reducing noise. When smaller pixels are compressed into a smaller area, noise is increased due to transference of information from one pixel to another.

But another question logically follows from this. Consider the Canon EOS 5D camera with its 12-megapixel full-frame sensor. The new Canon EOS 5D Mark II has 21 megapixels on a sensor of the same size. You might conclude that the quality of the Mark II’s images would suffer from all those pixels packed into the same space. They must be smaller, right? In reality, the newest generations of D-SLRs have mitigated the problem of information transfer among packed pixels by improving the processing capabilities of the cameras. The result is that quality is greatly improved, even at very high ISOs, in both larger and smaller sensors.

I personally use full-frame sensors almost exclusively because of the larger and better-quality image file they produce. I make extremely large prints from those files. That doesn’t mean that professional work can’t be accomplished with the less expensive APS-C-sized sensors.

The Silent Click
Q
What tips do you have for making a digital SLR less noisy? Under some circumstances mine can really spook a subject, more so than my film camera, which was pretty quiet.
J. Yett
Fowler, Colorado

A It’s frustrating when you take the time to carefully approach a wild subject, or you’ve spent long, hot hours in a blind waiting for the animal to approach you, and the first click frightens the subject into flight. But usually, this doesn’t happen. The initial click typically gets their attention, but once the sound has been accepted, subsequent intermittent firings tend to be ignored by most subjects.

You’re not going to find a silent digital or film SLR because the noise actually is made by the movement of the mirror as the image is captured. There are some D-SLRs that offer a “silent” mode, which just extends the time between the capture and the mirror’s slap. Another thing to avoid with sensitive subjects is the “let-her-rip” technique we tend to use with digital SLRs with capture rates as fast as 10 frames per second. That repetitive sound is almost certain to cause alarm.


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