Difficulty getting good Depth-of-field pictures

Discussion in 'Canon' started by Ken Kelley, Aug 24, 2008.

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  1. Ken Kelley

    Ken Kelley Member

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    I am using a Canon early Rebel with a EF 17-40mm lens and am having trouble getting pictures with a good range of "in-focus" for subjects where lighting is good, but even with extreme manual settings, I cannot keep a subject from 6ft to 20 feet in focus throughout. Can anyone help me with recommending a lens, that has excellend Depth-of-field, or technique? My movie camera has a small lens that does a much better job of Depth-of-field than I can do with my Canon. Thanks.
     
  2. usapatriot

    usapatriot Well-Known Member

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    You must use a small lens aperture like f/16, f/22, etc or smaller.

    Also the farther you are zoomed out the more DOF you will get.
     
  3. Ken Kelley

    Ken Kelley Member

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    Thanks usapatriot for your quick response to my DOF issue. Your second line answer about farther away from the subject is very appropriate, however, due to limited space in a small room (I photograph model train layouts) this is not always possible. I've even tried taking pictures on a tripod with a delay shutter opening using increasing time exposures to keep the aperture as small as my camera goes (f/22). Someone has told me about "pin-hole" lens that could possible help also.
     
  4. David Rasnake

    David Rasnake News/Review Writer News/Review Writer

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    How are you focusing the camera, Ken? Using AF, or setting it yourself? I'm thinking the concept of hyperfocal distance may be helpful in getting a focal setting that works at a high aperture on a tripod.

    dr
     
  5. Ken Kelley

    Ken Kelley Member

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    I have tried both ways of focusing (AF & Manual). On nearly all of my pictures I get a very clear focus at the beginning of the subject, or at the 1/3 area along the subject (when I set it manually). It's just that the range of "in-focus" (or what I call DOF) is narrow when I would like it to be very broad (along several focal points/distances). I appreciate all the wonderful comments, and I am still trying to master the DOF issue. The best pictures I get with a marginally acceptable DOF are those I take with bright light and manual settings of film speed, aperture, and time. It should be easier to get sharp pictures with the camera and lens I'm using, but I'm willing to try a different lens if this would solve the issue.
     
  6. David Rasnake

    David Rasnake News/Review Writer News/Review Writer

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    By my math, on a Digital Rebel with a 1.6x crop factor shooting at 17mm, f/16 and focused manually at 3 feet, you should get a depth of field area that shows sharpness from around 1.5 feet to basically infinity (beyond 50 feet).

    First, f/22 is probably overkill, and may be hurting your sharpness with difraction and causing you to perceive that the shot's not in focus when it actually is. I'd shoot no higher than f/11 to f/16, which should give you all the DOF you'll need in this case.

    The trick to maximizing depth of field is actually usually to "underfocus" your subject - to focus short of where you would normally focus. I'm betting that you're not getting uniformly sharp shots mostly because you're both manually and automatically focusing at or near infinity. Instead, try manually setting your focus to around 3 feet using the distance scale on the lens and work from there with an f/16 aperture: the shot may look out of focus in the viewfinder (because what you're seeing is the image at the lens's maximum aperture, and not what the sensor will "see" when it stops down the lens to take the image), but I'm betting the result will be much better.

    dr
     
  7. Ken Kelley

    Ken Kelley Member

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    I like your math David (1.5ft to infinity, if it works will do wonders for my DOF issue) Wow! You have given me a series of new ideas to try. The "underfocus" is something I have not tried before so I will begin experimenting over the next day or two and let you know what my result are. Thanks for your very interesting reply.
     
  8. Ken Kelley

    Ken Kelley Member

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    I am still trying several of David Rasnake's sugestions. The first few attempts at trying f16 at 17mm did not seem to improve the DOF. I also not sure what "1.6x crop factor" means? I'm still playing with several attemps to improve DOF, but so far I am not having much luck.
     
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