Focussing and DOF

Discussion in 'Photography' started by Nemos Janitor, 17 May 2009.

  1. Nemos Janitor

    Nemos Janitor

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    Great Pic's Rory

    Hope you do not mind me asking. Not criticising. The two Pics of the plate coral look like to me that they were taken on macro. This would explain the brilliant focus at the front of the pic's and the slight bluer towards the back. Having taken and seen these pic's what would you suggest might improve the focus. Please don't get me wrong here. If I don't ask, i will not learn.:smartass:
     
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  3. Rory

    Rory Admin MASA Contributor

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    From what I understand the higher the aperture (higher being a lower number) the shallower the DOF (depth of field, the area in focus) but more light is let in so the shutter speed can be relatively faster.
    In english the more light the lens lets through the shorter amount of time the shutter has to be open to capture enough light to have the photo bright enough.

    I generally use a wider aperture because I'm hand holding the cam. If you use a smaller aperture you can achieve a higher DOF so more stuff will be in focus but then the shutter speed will have to be slower, so if you were hand holding you would get more blue and then everything being in focus wouldn't really matter.

    Macro lens generally have a very shallow DOF. Take a look at the pic of the urchin on Sean K's thread for a good example. The lens I'm using is not macro, it does a max reproduction ratio of 1:3.2 as opposed to "true macro" at 1:1.



    So indirectly use a tripod to take the pics, maybe use aperture priority mode ("A" or "Ap" usually) and rotate the dial or do whatever you need to on the cam to set the aperture number quite high (like 14+). The camera will select the right shutter speed for the correct exposure. Also note that it doesn't help if the cam is on a tripod but the subject is moving, so pumps would have to be turned off etc. I didn't use a tripod or turn off pumps or anything for any of these photos. (The flash was on the tripod for the last few)
     
  4. Nemos Janitor

    Nemos Janitor Thread Starter

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    Rory, thank you for you answer. I have not progressed to that stage yet. All my Pic's are on auto mode and i am experimenting there for now. I was just interested to know where one should have focused on the subject. I am trying to get the hang of that first before playing around with the shutters & other things that can be changed.

    Maybe these posts should be moved to the new photography section for others to view.
     
  5. seank

    seank

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    Rory, the urchin pic I deliberately took of the centre out of focus to be able to see the feather dusters on the outline of the urchin better and still not "loose" the subject. Hope I explained myself. Btw, I take pics the same way you do, I have the camera in hand and never turn off any pumps- It is difficult and you take a lot of pics at different settings, but I feel that every now and then you do get that betterish pic
     
  6. Rory

    Rory Admin MASA Contributor

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    Not saying it was "wrong" or anything, was just a convenient photo showing the effect well :p
    There is no right and wrong with photography, however there is **** and awesome though ;)

    Will post some pics now showing DOF nicely, just need to resize and upload.
     
  7. Rory

    Rory Admin MASA Contributor

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    [​IMG]
    [​IMG]

    One of these pics was taken with a small aperture (f25) therefore took 1.6 seconds to take, but everthing is in focus. The other at a large aperture (f5.3) therefore more light was let through and it could be taken at 1/13s.

    The "glowy circles" in the background of the more out of focus one are known as "bokeh".

    Tripod was used for both.
     
  8. seank

    seank

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    the last pic looks better:whistling:
     
  9. Rory

    Rory Admin MASA Contributor

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    These pics were purposefully taken with a low aperture to make the background out of focus.

    [​IMG]

    [​IMG]
     
  10. Rory

    Rory Admin MASA Contributor

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    Yeah I used the pincushion on purpose because I've seen lots of pics of pincushions where only part of it is in focus. On pincushions it's quite noticeable because you have the bits sticking up in the background, foreground and in the middle and you can only focus on one of them with a large aperture.
     
  11. Warr7207

    Warr7207

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    Rory, what do you charge for lessons ?
     
  12. Tony

    Tony

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    Also bear in mind that one can get faster lenses which give apertures of 2.8 which lets in tons of light. This is more for wildlife photography but can work especially with fish who don't really keep still. Unfortunately they bear a higher price tag than lenses that start at apertures of 5.6 and up
     
  13. Rory

    Rory Admin MASA Contributor

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    Lol Warren...

    Yep an f2.8 lens is great for shooting moving objects.

    The cheaper lenses are generally f3.5 - 5.6 (the max aperture becomes smaller as the lens zooms). A "good"(read: expensive) zoom lens will usually have a fixed aperture (ie. max is f2.8 at any focal length). You won't find a lot of lenses slower than f5.6 because the camera's actually battle to autofocus because there isn't enough light coming through the lens. Conversely, "fast" lenses as in lenses with a low aperture are usually faster at focussing, but this is also because they're generally more expensive and thus the users are more demanding.
     
  14. viper357

    viper357 Admin MASA Contributor

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    [​IMG]

    Off topic for a second but have you got an ID on this fish? Thanks.
     
  15. crispin

    crispin

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    stop hijacking threads and use google noob! :)
     
  16. Tony

    Tony

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    Pseudanthias tuka (female)
     
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