Aperture help!

Discussion in 'Photography Beginners' Forum' started by nightflowre, Jun 6, 2009.

  1. nightflowre

    nightflowre TPF Noob!

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    Dear all,

    I need some help on this.

    The other day I went to the mountain. I was on top of it overlooking a terrace rice field in the valley below. I shot a photo and set the aperture to very small, it was probably around f/29. And the photo came out like this:

    Terrace rice field

    (Sigma 70-300, photo shot at 300 mm)

    My question it: If this was your case, what would you set the aperture to be? In my case the photo doesn't look sharp and that upsets me.

    Great thanks to any answer of yours! Cheers, mate!
     
  2. farmerj

    farmerj TPF Noob!

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    Did you use a tripod or rest of any kind?
     
  3. nightflowre

    nightflowre TPF Noob!

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    I did, farmerj. Thanks for your question!
     
  4. Samanax

    Samanax TPF Noob!

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    How much post processing work did you do to this picture?

    Does that Sigma usually shoot sharper images at the long end?
     
  5. nightflowre

    nightflowre TPF Noob!

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    @Samanax: I actually did not do much to that photo apart from resizing it.

    I don't think this one is good at its end!

    Thank you for your coming, Samanax!
     
  6. Samanax

    Samanax TPF Noob!

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    What photo editing program are you using? You might want to try sharpening the image a little.
     
  7. LarryD

    LarryD TPF Noob!

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    I agree that the photo does not look as sharp as you might like...

    My first question might be..."Why did you feel that f29 would be appropriate?"

    Generally the good f-stops might be between f-8 and f-16........ only going up to the higher or lower stops if the conditions absolutely won't let you get the shot any other way..

    An aperture that small will require that your speed be slow, or ISO high. A slow speed and you can introduce more camera shake/ wind movement/ mirror slap..etc. The higher ISO and you will introduce noise..

    It is a nice composition...well worth taking again at a couple of different settings...

    And as has been alluded too....... don't forget to sharpen if necessary in post processing..
     
    Last edited: Jun 6, 2009
  8. Dwig

    Dwig TPF Noob!

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    While extremely small apertures do provide a lot of depth of field they also noticably, severly in some cases, reduce overall resolution.

    This particular subject does not require very much DOF; everything is quite far away and nothing in the near foreground intrudes on the image. For a shot like this you would be vastly better off at a much wider aperture.

    I would choose an f/stop about 2 stops from the lens' maximum aperture. Stopping down a bit to avoid the optical flaws that show more at the wider apertures, but not so far as to limit the resolution due to the diffraction issues that arise at the smaller apertures. According to this review, the Sigma 70-300 f/4-5.6 DG Macro APO performs best between f/11 and f/16 with image quality falling off severly as you get to f/32:

    http://www.slrgear.com/reviews/showproduct.php/product/230/cat/31
     
    Last edited: Jun 6, 2009
  9. Josh66

    Josh66 Been spending a lot of time on here!

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    You're loosing sharpness from diffraction.

    Read this, it should clear it up for you.
     
  10. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Josh has good information for you.

    F/29 is a very small aperture. That means the shutter speed is be long. Any movement of the camera while the shutter is open will degrade the sharpness of the focus.

    Movement of the camera, even if on a tripod, can come from: actuating the shutter release, mirror slap or wind.

    In that image an aperture of f/11 or f/16 would probably been more than sufficient and would have allowed a much shorter shutter speed also

    You might want to make a critical examination of your tripod to ensure it is really as stable as you hope it to be.
     

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