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Thread: Trouble getting perfect focus

  1. #1

    Trouble getting perfect focus

    Hi All,

    I'm fairly new to photography and am currently taking some classes which require a pic having a shallow depth of field. I took about 25 pics of this flower and had trouble in all of them getting perfect focus of my subject. This was the closest I came to my goal but, as you can see, most of the anthers are not clear as well as some of the petal on the left. Any suggestions on how to correct this would be welcome. Thanks!

    Greg
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    Last edited by pixeltrek; 30th May 2012 at 09:45 PM.

  2. #2
    Moderator Dave Humphries's Avatar
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    Re: Trouble getting perfect focus

    Hi Greg,

    Welcome to the CiC forums from me.

    I don't see a picture - you may find this thread useful to have another go -
    HELP THREAD: How can I post images here?

    Hope you're successful soon,

  3. #3

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    Re: Trouble getting perfect focus

    I can see the picture so try this: If you have a manual control of your Focus take a 5-point cross type (if you have a lot of F-points) or take a single F point and place it on to the flower. Angle your camera just a bit so it sees the leaf behind, press shutter half way down (hold it that way), return to the angle in which you shot this picture and press shutter all the way down.

    If you don't have manual focus you're gonna have a little bit of hard time doing it because you have to listen to the camera. Do it the same way (1st angle, shutter half way, 2nd angle, shoot) without the tripod. only use it if your hands are really shaky. I hope you get it. Good Luck.

  4. #4
    rtbaum's Avatar
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    Re: Trouble getting perfect focus

    Ironically, you have indeed demonstrated shallow depth of focus quite well, you could reshoot this by positioning your camera on plane parallel to the plane of your subject, the rose. Maybe close aperture a little more to increase depth of focus and of course use a tripod.

  5. #5

    Re: Trouble getting perfect focus

    Thank you both for the suggestions. I do have manual focus & will try the 5 points. I will also do the parallel plane. Much appreciated.

  6. #6
    Sunray's Avatar
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    Re: Trouble getting perfect focus

    If your camera has live view it can help you in manual focus mode. Use live view and set the it to a high magnification (e.g. x5). You can easily recognize what's sharp at the flower on your camera display.

    Robert

  7. #7
    DanK's Avatar
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    Re: Trouble getting perfect focus

    Greg,

    The starting point is what Randy wrote: you are encountering narrow depth of field (DOF). This is inevitable with closeups. The question is how to deal with it. Here would be my steps:

    1. Decide how much you actually want in focus. You may want everything in focus, but you may not. For example, there are a lot of very nice flower macros that have the anthers in focus but let the petals behind them blur. (blur in front of the point of focus is often distracting, but blur behind usually isn't.)

    2. If you decide that you want to maximize DOF, one step is the one Randy recommended: minimize the DOF you need by making the subject as close to parallel to the sensor as you can. Of course, there will be some compositions for which this does not work, but it is OK for many.

    3. Stop down (smaller aperture, larger f/stop number). As you stop down past a certain point (which will vary with your camera), you will gradually introduce softening from diffraction. However, my experience has been that with closeups of flowers, the extra DOF more than offsets the diffraction, in terms of the overall impression of sharpness. You will have to experiment with your camera, but I have been able to shoot flowers down to f/20, printed to 8 x10 (roughly A4?) without a problem.

    4. Focus on the point you most want to be sharp. Usually, this is the anthers. I use either manual focus or center-point-only AF for this.

    Hope this helps

    Dan

  8. #8

    Re: Trouble getting perfect focus

    A sincere thanks to all who have replied to my post. The advice has been extremely helpful. I have also been very humbled... I have MUCH to learn about photography and have great respect for those who are willing to share what they know. Thanks again.

  9. #9

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    Re: Trouble getting perfect focus

    I would point out another disregarded factor.

    Due to the high saturation of the red colour of the flower, this colour channel has been over-exposed, so that no structure can be seen in large parts of the petals. This is very disturbing and reduces the feeling of "sharpness" in the image.

    As the DOF was supposed to be shallow, the image does reflect this rather well, and would have done so even better if less exposed, in order to keep the red tones well separated. Much of the impression of "unsharp" is due to the high saturation of red and blockage of high levels of red.

    When you take RAW, often this kind of over-exposure may be alleviated by decreasing saturation, but mostly, even the RAW image has one or two channels blown out when this occurs. My experience is that often you must decrease exposure up to two full stops, i.e. a minus 2 compensation, in order to catch the full tonality of the petals. This greatly improves the sense of sharpness in the image.

    You may see the over-exposure/saturation in the histogram, as a histogram curve rising at the right side instead of terminating exactly in the lower right corner. When you study the individual histograms for each channel, you can see that one or two of them reach some height at the right side, "leaning up the right wall". This always is to be avoided, while you can always allow the histogram to rise at the left side. Here, both the red and the green histograms show signs of over-exposure, although it is the red one that is most disturbing in the image.

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