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Closing the aperture

Discussion in 'Pro/Adv Discussion' started by ebfoxbat, May 2, 2015.

  1. ebfoxbat

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    Just thinking out loud here...

    Anyone thought about adding a lens cover that reduces the aperture of the lens to increase sharpness?

    Optically, I don't know if a smaller aperture in front of the optics would sharpen the image like one behind the optics would. I understand it would narrow the field of view, but I'm wondering if the sharpness gain (and thus better resolution) would be worth it.
     
  2. Meta4

    Meta4 Moderator
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    1. It would reduce the amount of light getting to the sensor significantly
    2. Unless the lens was designed for it, it's unlikely to work as you propose
    3. The lens is the equivalent of a 20º lens in 35mm photography and has very good depth of field
    4. Because in aerial photography, the subject is usually distant from the camera, you don't need more depth of field.
    5. Increasing depth of field (what you called sharpness gain) can't change resolution - that's set by the sensor.
     
  3. ebfoxbat

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    Only if you significantly closed the aperture. I'd trade a stop or two for sharpness, say f/4

    Lens design doesn't change the physics of light.

    I'm not talking about depth of field. The sensor is so tiny on the P3's that there's tons of it anyway.

    Agreed, but not relevant to this thought.

    No what I'm calling sharpness gain is actually a reduction in aberrations that come with a smaller aperture. It would manifest itself as better micro contrast which the human eye and brain would see as being sharper. It would effectively resolve more (thus my "resolution gain"), however the final image would need to be cropped so it would have smaller final dimensions.
     
  4. Meta4

    Meta4 Moderator
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    Make an experimental model using a small hole in black card in front of an SLR using a 20mm lens wide open. See how it goes.
     
  5. ebfoxbat

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    A small hole in front of an SLR lens would introduce diffraction. I'm talking about a slightly smaller aperture than the stock optics.
     
  6. JayB

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    I believe you work out the actual size of the aperture by dividing the focal length by the aperture so 20 / 2.8 = 7.14mm. Clearly this is between the lense and sensor, I'm not sure by placing something in front of the lense it would have the desired effect as the light being focused on the sensor will still be passing through the 2.8 aperture. You will reduce the amount of light but this will just reduce the shutter speed, similar to adding a ND filter.

    This is just my logic with my limited knowledge of photography.
     
  7. Buzz313th

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    On the P3 or any other Small "Action Camera" there is no Iris.. The barrel is wide open to allow for as much light to enter the lens as possible and to keep the weight and cost down. If you used an external Iris to restrict before the front element, you would destroy the lens optics and it would result in less light, less contrast and optical sharpness, and probably vignetting.

    Regardless of optical clarity, you will still be getting the same resolution you are set to shoot at. Some tips to help get better optical clarity on the P3.

    1. Remove the lens cover (Transparent sticker) that comes on it ourt of the box.

    2. Keep the front element clean

    3. Try to avoid lens flare

    4. Use a polarizer in high contrast lit scenes especially if reflections and refraction is involved

    5. The P3 looks like it set to slightly overexpose.. Try setting EV compensation at -1/3rd to -2/3rds

    6. Pick scenes to shoot that have a good overall contrast range for the P3 camera.
     
    #7 Buzz313th, May 2, 2015
    Last edited: May 2, 2015
    skyhighdiver and Meta4 like this.