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Tuesday, October 25, 2011

The Colors Of Snow

Antarctica And Other Snowy Venues • Lost Pixels • Taking The Long Road • Presentation Programs • Photos On The Level

Labels: How-ToColumnTech Tips
Lost Pixels
Q How can I keep my image files from losing their quality? Does opening a file in Photoshop too often make it worse? I printed an image that was taken just two years ago, and the pixels in the sky were showing! How can I prevent that from happening to my other images?
P. Johnson
Via Facebook

A The passage of time doesn't degrade an image file. But JPEG files lose data every time they're opened and resaved; the file actually becomes smaller. You can avoid this problem by storing your files in TIFF and Photoshop (PSD) formats because these can be opened, closed and saved as often as needed without any loss of quality.

This offers me a good opportunity to remind everyone about proper file storage. You can lose your images forever with hard-drive failure, so always back up your files to portable drives and keep a set of these away from your computer, in a bank vault or a friend's home. If you have a lot of images backed up on CDs or DVDs, it's time to take a good look at them and transfer them to more reliable media.

There can be many reasons for the pixelation of the sky in an image. If yours isn't a JPEG file that has been opened and resaved numerous times, the pixelation may have been there from the beginning. If you shot the file as a JPEG (8-bit), banding may appear in the sky due to lack of sufficient information—that is, poor image quality. Shooting in RAW mode (16-bit) captures much more image data for smoother gradations. Noise from expanded ISO captures is also more evident in the sky than in more detailed areas, and this presents itself as a multitude of red, blue and green pixels. Finally, be careful about how you're processing your images in Photoshop. Areas of consistent tone can appear to be pixelated due to oversharpening of the image. This might work for the foreground detail, but has the effect of sharpening individual pixels in an area such as the sky.

Taking The Long Road
Q I'm thinking about getting my first supertele lens. You've said in the past that your supertele lens of choice is the Canon 500mm, not the 600mm, due to the extra weight of the 600mm. Now that the new Canon 600mm weighs closer to the old 500mm, would you still suggest getting the 500mm instead of the 600mm (cost factor aside)? With your 500mm, do you often need to use a 2x tele-extender to get enough reach? The lens will be used for large birds and animals on safari and small birds later.
Via email

A Supertelephoto lenses are a big commitment both in cost and technique, but they open new worlds of possibility to photographers of birds and other wildlife. The 500mm is still my first choice for these subjects, and I've taken it on a number of African safaris. You'll find that there's never enough "reach" when photographing elusive wildlife, especially small birds. I always carry 2x and 1.4x tele-extenders with me, as well as an extension tube to facilitate closer focus. I have on some occasions actually stacked both the 2x and the 1.4x tele-extenders, offering a 1400mm telephoto with a maximum aperture of ƒ/11. Due to the advanced capabilities of today's DSLRs, a higher ISO can be used, making ƒ/11 a manageable ƒ-stop with a reasonable shutter speed.

The new 500mm Mk II and 600mm Mk II telephotos from Canon are smaller, lighter and purportedly sharper than their predecessors. Unfortunately, they're also considerably more expensive. Given the choice of the new supertelephotos, I would still go with the 500mm. Smaller and more versatile still trump a larger lens when traveling and occasionally handholding the lens in the field. I often photograph from kayaks and while stalking small birds, in which cases, using a tripod isn't possible. Still, every movement is magnified with a supertelephoto, so be sure to invest in a sturdy tripod and a robust ballhead for your long lens, and use it faithfully whenever conditions allow.


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