Results 1 to 12 of 12

Thread: Aperture size vs image sharpness

  1. #1
    Member
    Join Date
    Nov 2003
    Location
    The North
    Posts
    639

    Default Aperture size vs image sharpness

    Hi!

    Is there any relation between image sharpness and aperture size? Tot i read it somewhere in one of the threads...but not too sure bout it. As in excluding the depth of field, any other effect on sharpness of image?

    And what does it mean by a fast lens? Smaller f-stop?

  2. #2

    Default

    fast lens means small numbers
    so you can take at faster shutter, so its called fast lens

  3. #3
    Member
    Join Date
    Oct 2003
    Location
    Singapore, East
    Posts
    371

    Default

    Quote Originally Posted by phantasia
    Hi!

    Is there any relation between image sharpness and aperture size? Tot i read it somewhere in one of the threads...but not too sure bout it. As in excluding the depth of field, any other effect on sharpness of image?

    And what does it mean by a fast lens? Smaller f-stop?
    Yes!! there's relation between sharpness and aperture size/f number!

    Aperture controls the depth of field of your picture.

    The bigger the aperture hole (f number at the smallest), the LESS depth of field in your picture... which means the subject that you wanna take will be in focus (sharp) and the background will be blurred.

    The smaller the aperture hole (f number at the biggest), the MORE depth of field in your picture... which means the subject and the background will be in focus. everything will turn out sharp.

    A bigger aperture size (f number smallest) allows more light into the camera. Therefore the shutter speed of the camera can be faster than the camera with a smaller aperture size.
    This is why people term this as fast lens.

    Hope this helps...

  4. #4

    Default

    I think you may be talking about the sharpness of the lens when stopped down (other than affecting the DOF). Most lens do not display full sharpness when stopped wide open; to achieve maximum sharpness you usually stop down the lens 1-2 stops. You scarifice a bit of DOF for that, but you will have sharper images.

  5. #5
    Member
    Join Date
    Aug 2002
    Location
    Singapore
    Posts
    293

    Default

    Quote Originally Posted by phantasia
    Hi!

    Is there any relation between image sharpness and aperture size? Tot i read it somewhere in one of the threads...but not too sure bout it. As in excluding the depth of field, any other effect on sharpness of image?

    And what does it mean by a fast lens? Smaller f-stop?
    The performance of a lens, in relation to its aperture size, is unique. Generally, lenses are supposed to give optimal sharpness around the mid-aperture range. For example, for a lens that has aperture values from f/2.8 to f/22, you will probably get good results around f/8. However I must stress again that it's best that you shoot at all apertures under the same condition to find the so-called "sweet spot" where your lens performs best. As an example, the portrait lens that I've used, the Nikkor 105mm f/2.5 AI, gives me better results at f/4 rather than f/8 although I am aware that many other users get best results at f/8. So happy shooting!

    andrew

  6. #6

    Default

    strictly speaking..not really related:

    aperture size =how much light the lens can let in

    image sharpness=how well the lens can resolve the image.

    but then again nowadays most large aperture lenses are specially designed to be of top optical quality..so u get to enjoy both fast arpetures and sharp images as a whole package in the same lens

  7. #7
    Member
    Join Date
    May 2003
    Location
    Singapore
    Posts
    984

    Default

    everyone,
    all lenses have an optimum sharpness and this often is not at its maximum apperture. this usually occurs when the lens is stoped down one or two stops from maximum apperture....

    maximum apperture sometimes gives lightfall off and the contrast might not be so good.

    this is what the starter of the thread means to discuss about.
    similar with what kh_drew is explaining.
    waht surftec is explaining is know as depth of field and not lens sharpness.
    Last edited by showtime; 11th December 2003 at 11:21 PM.

  8. #8
    Member
    Join Date
    May 2003
    Location
    Singapore
    Posts
    984

    Default

    Quote Originally Posted by Ah Pao
    I think you may be talking about the sharpness of the lens when stopped down (other than affecting the DOF). Most lens do not display full sharpness when stopped wide open; to achieve maximum sharpness you usually stop down the lens 1-2 stops. You scarifice a bit of DOF for that, but you will have sharper images.
    when you stop down 1-2 stops, you INCREASE the DOF not SACRIFICE it...
    just need to clarify this fact to the rest. because its really fundamental that we understand DOF and apperture relationships.

  9. #9

    Default

    Quote Originally Posted by phantasia
    Hi!

    Is there any relation between image sharpness and aperture size? Tot i read it somewhere in one of the threads...but not too sure bout it. As in excluding the depth of field, any other effect on sharpness of image?
    :
    when shoot wide open, most lens will not deliver it sharpest image. Most lens work pretty well at F8.
    however we need to use apperture like i.e F2.8, F5.6 at times cause we need the shutter speed or when we actually wan a shallow DOV to isolate objects.
    i.e: indoor, correct exposure is 1/8 , F8, in general this will give you a blur image due to motion blur and handshake prob, but say at F2.8, you get 1/60s, which can pretty well get you a decent sharp image, considering you have use the DOV properly.


    Quote Originally Posted by phantasia
    And what does it mean by a fast lens? Smaller f-stop? :think
    :
    fast lens in general refer to lens w F2.8 or lower.

  10. #10
    Member
    Join Date
    May 2003
    Location
    East
    Posts
    706

    Default

    A shallow DOF does not mean that the image is not sharp. It just means that it has a shallow DOF period. The subject in focus can still be sharp.

    Generally, the sharpest images can be produced at the smaller aperature sizes.

  11. #11
    Member
    Join Date
    Dec 2003
    Location
    Singapore
    Posts
    332

    Default Aperture and DOF/Sharpness

    For most lenses, the optimal aperture for the best sharpness is f/11 or f/16. Beyond that, diffraction sets in and takes away any DOF advantage the smaller aperture offers.

    Wide angles generally have better DOF than telephoto lenses.

  12. #12

    Default

    Quote Originally Posted by showtime
    when you stop down 1-2 stops, you INCREASE the DOF not SACRIFICE it...
    just need to clarify this fact to the rest. because its really fundamental that we understand DOF and apperture relationships.
    Yeap, sorry for my mistake. I was thinking towards the fact that you increase the DOF with a smaller aperture, and hence so-called 'scarifice' the ability to take shallow DOF shots.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •