Monthly Archives: August 2007

Stories

About Those Clouds

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Last week I did a bit of flying, first to the Midwest (South Dakota, to be specific) and then to Seattle before returning to the San Francisco Bay Area.

I’ve always preferred window seats – I love to watch the land passing below. I keep my camera nearby and when I see something interesting I photograph it. On this trip I flew out of the Bay Area in the early morning, so there was very interesting low light on the clouds early in the flight.

I also photographed some areas of Seattle on this trip, and I’ll post some photos starting next week. A few are fairly traditional “touristy” shots, but I’ve also been experimenting with some extensive post-processing modifications. Some of the photos are not at all like my usual stuff, but I’m having an interesting time trying out something new and learning more about PS in the bargain.

You may even get to see some of my “street photography.”

G Dan Mitchell is a California photographer and visual opportunist. His book, “California’s Fall Color: A Photographer’s Guide to Autumn in the Sierra” (Heyday Books) is available directly from him.

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Technique

From Here to Infinity?

4 Comments

Greg writes:

I’ve enjoyed your photography that I’ve found on your three websites. I especially enjoyed your photos of the Sierras. While looking at your photo “RitterBannerEdizaFlowers2007_07_25.jpg” [see below] the question comes to mind, “How did he get everything from 12 inches to infinity in focus?”

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Mounts Ritter and Banner, Ediza Lake. Sierra Nevada, California. © Copyright G Dan Mitchell.

(Greg also noted that current Canon EF lenses generally do not include a DOF scale.)

Thanks for writing, Greg.

The main technique in this photo is the use of a short focal length wide angle lens. It (along with similar photos in my gallery) was shot with the Canon EF 17-40mm f/4 L lens, which is an ultra-wide angle (UWA) lens on the full-frame Canon 5D. Such UWA lenses can produce an extraordinary depth of field – it may not be quite “12 inches to infinity,” but it is pretty close.

In addition, one can shoot at smaller apertures on a full frame DSLR compared to the crop sensor DSLRs. On a crop body you generally avoid apertures smaller than f/8 or so, especially if you are planning to make a large print. At smaller apertures, diffraction decreases the maximum sharpness of the image. You get greater depth of field, but the cost is that the sharpest portions of the image in the plane of focus actually become less sharp than at optimal apertures. With a larger sensor (or larger film), diffraction doesn’t become significant at f/8. I conducted some experiments with my L lenses and 5D and discovered that sharpness in the plane of focus is at least as good at f/11 as it is at f/8, and that focus plane sharpness at f/16 is virtually indistinguishable from f/8 and f/11.

So, by combining a very wide angle lens (I believe it was 17mm in this photo) with a very small aperture (f/16 most likely) and focusing just beyond the closest object in the frame, I can achieve very wide DOF.

There are a few other tricks that one can employ. Faced with scenes that have an extremely wide dynamic range, I often take two exposures with one set for the darker areas and the other for the bright areas. In a situation where the foreground is dark and the distant objects light, I can also slightly shift the focus between the two exposures. (I combine the two images in post-processing; this is more or less equivalent to using ND grad filters at the time of the exposure though it permits more flexibility at the expense of an extra exposure.)

– Dan

BTW, Greg also reminded me of an interesting SF Bay Area show that is about to close:

P.S. You had an earlier post about the Yosemite art exhibit at Stanford. I’d like to bring to your attention another Yosemite exhibit that is currently running through Aug 26 (ends soon!) at the Oakland Museum (http://www.museumca.org/). This is an enjoyable exhibition that covers the art of Yosemite from native american basketry, to mid-19th century painters, to photography; highly recommended!