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!

4 thoughts on “From Here to Infinity?”

  1. First, I would not focus on infinity. Since the DOF zone extends in front of and in back of the plane of focus, there isn’t much “in back of infinity” to include in the DOF… :-)

    If a central object is some distance into the scene I may well focus on it – since it will be central in the final image I want it to be as sharp as possible, the theory being that slight blur on a non-central element of the scene will be noticed less than blur on the central object. (If memory serves, this is pretty much what I did in the photo above.)

    If there isn’t anything like that I have to convince that I more or less “focus a little ways into the scene.” But I also use the depth of field preview button to check the results of this. And I’m definitely not above taking more than one exposure and altering the focus point between them. While that may not have been quite as viable with film, with digital, “why not?” I’m using 8GB cards, and if it takes multiple exposures of the scene to get the one I want, so be it.

    Dan

    Reply

  2. Thanks Dan. So where do you usually focus on ? the object ? infinity ? or 1/3 of the scene ?.

    TIA,

    John

    Reply

  3. Hi John:

    No, I never do any sort of formal calculation of DOF. There are several reasons for this approach:

    • If I really need maximum DOF I simply go for the smallest appropriate aperture, which on my full frame DSLR could be f/16 or f/22. At f/16 I find that there is no visible (at least in a print) loss of sharpness compared to f/11 (which generally appears to be the sharpest aperture when I pixel peep). I do not hesitate to use f/22 when I need it. There can be a bit of diffraction blur at this aperture, but again it is often completely invisible in a print, and if I need this kind of DOF (or a longer exposure, another reason for using a smaller aperture) then getting that is often more critical than squeezing out that last bit of sharpness.
    • After shooting quite a bit with my equipment I have a decent sense of what will and won’t work in terms of DOF.
    • If I’m concerned that DOF won’t be deep enough for the shot, I sometimes use “focus bracketing.” I make an exposure focused on a closer element of the scene and then make a second exposure focused on a more distant portion – then I combine the two images in Photoshop. (There are software solutions that purport to automate this process.
    • All too often I don’t have time to stop and consult DOF tables or do calculations when the scene is in front of me.

    Hope that helps… :-)

    Dan

    Reply

  4. Hi Dan,

    When taking landscape pictures do you use DOF calculator stuff ?. If not what do you use ?.

    TIA,

    John

    Reply

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