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Thread: a DOF experiment

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    Member michaellxv's Avatar
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    a DOF experiment

    I've just done an experiment with DOF and thought I would share the results to double check I have this right.
    The subject was a friendly raptor and I put the camera on a tripod and cycled through the settings.

    The first group is at 55mm and I went from f/5.6 through to f/36 to see the change in DOF.
    For the second line I moved the camera slightly back and repeated and I noticed that even this slight change made a significant difference in the result.

    The second group is at 18mm and f3.5 to f/22. The change in DOF is there but not so obvious as it was at 55mm.

    One thing I was not expecting was how much I had to get in the raptors face to make this work. I can now also see that the focal length plays an important role in this process. Are there any other setting I should be looking at with this experiment?

    combined.s.jpg

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    Administrator ricktas's Avatar
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    To do a good depth of field experiment you need something that offers a better differentiation for the viewer. With this set, at the size presented it is hard to see a lot of difference in each photo, except for little things like the foot on the left of frame in the top set. You would be much better off setting up a line of something small. marbles, batteries, even a ruler or tape measure works very welletc. Putting them all in a straight line and shooting at those from a slight angle. That sort of setup will result in a much more visually perceivable result.

    Not my images, so only posting links:

    http://farm5.staticflickr.com/4028/4...1386743e_z.jpg

    http://media.digitalcameraworld.com/...gon.step1_.jpg

    By using something repeatedly in a line, then setting your camera up and focusing on one point, you will display the depth of field across apertures in a way that is very easily understood by viewers of the photos. Whilst your dragon does show the effects of the differing apertures on depths of field, I feel a better example could be done, other than the dragon.

    I hope however that the experiment let you learn more about how aperture works and now how a better understanding of it, will allow you to select the aperture you want/need when you go out shooting.

    Depth of field has two main elements, the aperture selected and the distance to subject, there is a depth of field calculator here that can help you understand it more, while on the computer, and then you can put that into action with your experiments and photos
    Last edited by ricktas; 05-07-2013 at 7:52am.
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    Quote Originally Posted by michaellxv View Post
    Are there any other setting I should be looking at with this experiment?
    I suggest that you FRAME the head of the Subject EXACTLY THE SAME SIZE in your viewfinder using four different FOCAL LENGTHS of your zoom lens (i.e. 18mm; 24mm; 35mm and 55mm) and then at each FL take three shots at three different apertures (i.e. F/5.6; F/11 and F/22)

    And then compare the DoF for each same Aperture, at the four different Focal Lengths.

    WW

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    Thanks for the suggestions and links Rick. I learned a lot from the experiment but there is always more for me to learn.

    William, I will have a go at your suggestion. It sounds like a more realistic example for when I actually want to take a photo.

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    A royal pain in the bum! arthurking83's Avatar
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    Quote Originally Posted by michaellxv View Post
    ...... I can now also see that the focal length plays an important role in this process. Are there any other setting I should be looking at with this experiment?

    ......
    subject distance.

    Basically what William said (but with minimalist wording).

    That is, to maintain the subject of interest at the same size in the frame, you need varying distances for varying focal lengths.

    Obviously get in closer at the shortest focal length .. and then gradually move yourself(back) or your subject(away) to maintain the same size in the frame as the focal length increases.
    Nikon D800E, D300, D70s
    {Nikon} -> 50/1.2 : 500/8(CPU'd) : 105/2.8VR Micro : 180/2.8ais : 105mm f/1.8ais : 24mm/2ais
    {Sigma}; ->10-20/4-5.6 : 50/1.4 : 12-24/4.5-5.6II : 150-600mm|S
    {Tamron}; -> 17-50/2.8 : 28-75/2.8 : 70-200/2.8 : 300/2.8 SP MF : 24-70/2.8VC


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    Ausphotography Addict Lplates's Avatar
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    Good on you for doing the experiments. I remember doing something similar when I first got my dslr and it certainly made the info I'd been reading click in my mind and easier to understand.
    Glenda


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    Quote Originally Posted by michaellxv View Post
    Thanks for the suggestions and links Rick. I learned a lot from the experiment but there is always more for me to learn.

    William, I will have a go at your suggestion. It sounds like a more realistic example for when I actually want to take a photo.
    This may help Michael. - http://www.dofmaster.com/dofjs.html

    You set the camera, focal length, F Stop and Distance to object and you see the calculation change on the right hand side.

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    Quote Originally Posted by michaellxv View Post
    . . . I will have a go at your suggestion. It sounds like a more realistic example for when I actually want to take a photo.
    What was the result that you found?

    WW

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    Quote Originally Posted by William W View Post
    What was the result that you found?

    WW
    I read through the links provided and that helped a lot with the theory. I did a couple of test shots but haven't been out to do the systematic test that I want to do. I'll post the results when I do

    Michael.

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    Good Oh!

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    If you look at the series of photos at the top of the forums page, you will notice the space around the subject, in this case a young girl.
    This also allows the subject to stand out from the surroundings to help increase the impact of the photo and bring you eyes to the main subject. Also have a look at some of the bird, portrait and still life photos to help give you a bit more of an idea as to how DOF can be used.

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