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Thread: How to Test a Lens Sharpness

  1. #21

    Default Re: How to Test a Lens Sharpness

    Quote Originally Posted by Saabo King View Post
    Bravo!!! I finally got an idea of what I can do in the shop without doing funny things like shooting Ikea batteries etc........

    Thank you all anyway for the contributions. I will post the price of the lens and whether my purchase is successful.

    Cheers!
    Also, if you want to be more serious, your distance from your target matters too.. you can take focal length x 20 for your focusing distance, or even focal length x 60. (which means you move away as you zoom towards the longer end... No point shooting too close as any lens can be pretty sharp (or give the impression of sharpness) with close up shots.

    Usually camera shops will have a whole line of lens boxes, I usually use those when I'm just testing without buying... they work too.
    Looking for Canon 100mm F2 USM :)

  2. #22
    Senior Member geraldkhoo's Avatar
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    Default Re: How to Test a Lens Sharpness

    Sharpness is subjective... and you also need to have a reference point as to how sharp is sharp.

    I have found that most macro lenses are sharp. Get a macro lens and shoot and you will have an idea about sharpness to give you a point of reference. For example, my Nikon AFS 60mm Micro lens is sharp from f/2.8. My Tamron 17-50 f/2.8 is not as sharp as the 60mm Micro at f/2.8.

    Next, as a general rule of thumb, a lens is sharpest at about 2 stops from it's largest aperture. So, if my lens is a f/2.8 lens, switch to f/5.6 and shoot at that aperture. Make sure that other factors are same, e.g. no handshake, the focus point is the same, at the same ISO, etc. Also as another general rule of thumb, f/8 is generally considered the sweet spot aperture. Once you shot at that aperture, switch down to your largest aperture, e.g. f/2.8, and compare the photos. You will now see the difference in sharpness between the largest aperture, and a shot 2 stops away, or at f/8.

    By comparing the different pictures, then you can judge if the sharpness is acceptable to you.
    Last edited by geraldkhoo; 5th January 2009 at 09:48 PM.
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  3. #23

    Default Re: How to Test a Lens Sharpness

    Quote Originally Posted by geraldkhoo View Post
    Sharpness is subjective... and you also need to have a reference point as to how sharp is sharp.

    I have found that most macro lenses are sharp. Get a macro lens and shoot and you will have an idea about sharpness to give you a point of reference. For example, my Nikon AFS 60mm Micro lens is sharp from f/2.8. My Tamron 17-50 f/2.8 is not as sharp as the 60mm Micro at f/2.8.

    Next, as a general rule of thumb, a lens is sharpest at about 2 stops from it's largest aperture. So, if my lens is a f/2.8 lens, switch to f/5.6 and shoot at that aperture. Make sure that other factors are same, e.g. no handshake, the focus point is the same, at the same ISO, etc. Also as another general rule of thumb, f/8 is generally considered the sweet spot aperture. Once you shot at that aperture, switch down to your largest aperture, e.g. f/2.8, and compare the photos. You will now see the difference in sharpness between the largest aperture, and a shot 2 stops away, or at f/8.

    By comparing the different pictures, then you can judge if the sharpness is acceptable to you.
    That is a good way, but it generally has one weakness... you can catch the BBB instantly... The next thing you know, nothing is sharp except the top range. Lol.
    Looking for Canon 100mm F2 USM :)

  4. #24
    Senior Member Anson's Avatar
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    Default Re: How to Test a Lens Sharpness

    Quote Originally Posted by geraldkhoo View Post
    Sharpness is subjective... and you also need to have a reference point as to how sharp is sharp.

    I have found that most macro lenses are sharp. Get a macro lens and shoot and you will have an idea about sharpness to give you a point of reference. For example, my Nikon AFS 60mm Micro lens is sharp from f/2.8. My Tamron 17-50 f/2.8 is not as sharp as the 60mm Micro at f/2.8.

    Next, as a general rule of thumb, a lens is sharpest at about 2 stops from it's largest aperture. So, if my lens is a f/2.8 lens, switch to f/5.6 and shoot at that aperture. Make sure that other factors are same, e.g. no handshake, the focus point is the same, at the same ISO, etc. Also as another general rule of thumb, f/8 is generally considered the sweet spot aperture. Once you shot at that aperture, switch down to your largest aperture, e.g. f/2.8, and compare the photos. You will now see the difference in sharpness between the largest aperture, and a shot 2 stops away, or at f/8.

    By comparing the different pictures, then you can judge if the sharpness is acceptable to you.
    Thanks for the tip...

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