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Thread: Diffraction In Macro

  1. #1
    Mike Moats
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    Default Diffraction In Macro

    I have a lot of people ask why I shoot at f/32. Becuase it works for me. If I'm out shooting subjects where I want the whole image in focus (which is most of my images and the best sellers) I just set my f/stop at 32 and shoot all day with out regards to the subject whether it's flat or has a lot of depth, my f/stop stays the same. I can set my f/stop at one setting and not worry about it the rest of the day unless I decide to shoot a subject that requires a blurred BG. Most of the subjects that I shoot where everything is going to be in focus are subjects that are on the ground and not effected by wind, so even if I have a long exposure from shooting stopped down its still not a problem.

    Now I know all about diffraction from stopping the lens down, and have read and heard all about it, but in the real world it's not a problem that can't be fix in PS with some sharpening.

    Since I'm tired of explaning to people that it works, I finnally posted a test shot with a Tamron 90mm lens on my blog to show diffraction isn't a scary thing that should be avoided and something that can be corrected in PS the same as we correct, HDR, poor exposure, croppring, cloning out distraction, etc.

    I've had experiences with many different cameras and macro lens in my workshops and have seen excellent results with this style, unless someone has a total crap lens.

    I've been shooting this way since I started shooting and have yet to have a magazine editor, art director, art consultant, art buyer, and contest judge every tell me my images suffered from diffraction. :)

    To view the test on my blog go to, www.MikeMoatsBlog.com

  2. #2
    Fabs Forns
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    Thanks fr the great information and explanation, Mike :)

    MM rocks!

  3. #3
    Robert Amoruso
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    Similar with my landscapes, I almost always do them with the f/stop as small as possible and don't have a problem with diffraction.

  4. #4
    Mike Moats
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    Hey Robert, good to hear, I have people in my workshops that have been brainwashed into thinking they can't stop down, and even after I show them with their own camera they still shoot more wide open even when they're trying to get everything in focus, Da.

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    Hi Mike,
    I agree with your experience. I've seen some simply outstanding macro images. For example, perhaps you know Greg Lasley (http://www.greglasley.net/ ). He showed me some 13x19 inch prints done at high f/ratios that were simple amazing.

    But diffraction is a real effect. Here is an example that shows the blurring effect (see Figure 4):
    http://www.clarkvision.com/imagedetail/sampling1.html

    But more than just blurring is loss of contrast. See, for example figure 8 at:
    http://www.clarkvision.com/imagedeta...el.size.matter

    Yes, you can compensate to some degree with sharpening, but with other methods, you might be able to achieve sharper images, in case that was important. (Having said that, in the field, I'll be more concerned with getting the depth-of-field I want than concern over diffraction.) For example, check out helicon focus: http://www.heliconsoft.com/heliconfocus.html
    With this you can move beyond what you can do at f/32, or even f/128!

  6. #6
    Mike Moats
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    Hey Roger, I agree that there is a loss of sharpness from diffraction, but my point is that you can correct this with extra sharpening and fool our eyes and brain into thinking it sharp. Sure if we look at the pixels under a microscope we'll see some problems but we don't view our images under these conditions, I'm only concerned with what my eyes see and not the mathematical equations that say its a bad thing. I do use Helicon Focus if I'm shooting a subject that I need a blurred background by shooting wide open, but unable to get enough depth of field on the main subject, so I'll shoot mutiple focus points wide open on the main subject while maintaining the blurred background and then merge in Helicon. But when shooting subjects that I want everything in focus, I can acheve this with one shot by stopping down all the way.

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    Quote Originally Posted by Mike Moats View Post
    snip...

    But when shooting subjects that I want everything in focus, I can acheve this with one shot by stopping down all the way.
    Mike- Another option for increased DoF I suppose is a Tilt and Shift Lens. But do they work well for macro I wonder? Not sure of the close-focussing distance of the current crop. Would need an extension tube or two.

  8. #8
    Mike Moats
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    Hey John, I've never used a tilt-shift lens but I hear they work well. I don't have a problem getting enough DOF by just stopping down the lens, and has you see in my test on my blog the diffraction isn't a big issue and the adjustments needed are very simple in PS. Thanks.

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    Mike,
    The diffraction effect is also a function of pixel spacing and the blur filter. You may not be seeing the effects at your f/stops because of the large pixel spacing and blur filter of your camera. People with a different camera may see different issues. For example, a Canon 50D will likely show a greater effect because of its smaller pixels.

  10. #10
    Mike Moats
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    Hey Roger, your right each camera, and also lenses, will preform a little different with diffraction. I have to add more sharpening with my Sigma 180 than I do with the Tamron 90. In my workshops I teach this style of shooting and how to sharpen the image in photoshop, and I've had the opportunity to work with students using every DSLR and macro lens on the market, and have found that each system will require a little more or less in sharpening, but its not drastic and everyone comes away with acceptable images at the end of the day. When I say acceptable I mean to the eye, not under a microscope. Thanks.

  11. #11
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    Quote Originally Posted by John Chardine View Post
    Mike- Another option for increased DoF I suppose is a Tilt and Shift Lens. But do they work well for macro I wonder? Not sure of the close-focussing distance of the current crop. Would need an extension tube or two.

    Tilt/Shift will help if the subject is flat, or at any rate if the parts of the subject that need to be sharp lie in a plane. Lenses generally are designed to give sharp images of a subject lying in a plane that's parallel to the sensor plane. T/S rotates the plane of sharp focus so that it no longer is to be parallel to the sensor plane. So whether it will help depends on the subject's actual shape and whether the areas of desired sharpness lie in or close to a plane.

    Bill

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