Pinhole Problems

Discussion in 'Photography & Video' started by lfom5608, Jan 7, 2007.

  1. lfom5608

    lfom5608 Member

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  2. Julz

    Julz Member

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    dust on the sensor... its more visible because your aperture is extremely small (ie a pinhole).
    Try using a rocket blower on the sensor
     
  3. OP
    OP
    lfom5608

    lfom5608 Member

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    Ahh that makes sense. Cheers.
     
  4. CeeJay

    CeeJay Member

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    Interesting .. I just made my first Digital pinhole about two weeks ago ( between Christmas and New Years )
    I made my first pinhole camera (out of black cardboard paper), about 20 years ago when I was still in primary school , so this was a nice flashback to that time.

    I'm still tweaking the pinhole size and I'm going to try the method of denting the aluminium from a soda can and sanding it down until a hole appears.
    It should be possible to make an even finer hole that way.
    My current pinhole is made with a needle through some aluminium foil.

    My first pinhole attempt :
    [​IMG]

    My second pinhole attempt :
    [​IMG]

    As you can see there is definite improvement , the second pinhole yields much sharper images than the first, and hopefully I can get even sharper images in future attempts, through a combination of a finer pinhole and adjusting the focal length to the pinhole and not the other way around.

    It should be much easier to deal with the focal lengths millimeter margin of error, than the micrometer margin of error you have to deal with when making the pinhole.

    I found this guide :
    http://www.northlight-images.co.uk/article_pages/Canon_1ds_pinhole.html

    I'd like to make a DIY extension tube , but not out of toilet paper tubes like he did .. That would likely cause dust from the tubes to gather on the sensor.
    Any ideas ?

    It doesn't have to be very long as I only instead to use it to focus the image.
    I was thinking that if I could find a container with a screw on lid that had a very long thread then I could use that.
    Any kind of tube I can somehow adjust in length will do fine as well.
     
  5. Julz

    Julz Member

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    hey may I ask, what is the field-of-view equivalent to if you make the pinhole camera just using hte body cap?

    Does it make a wide angled lens?
     
  6. aloysius

    aloysius Member

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    I think i read somewhere that the focal length of pure lens cap pinhole is roughly 50mm
     
  7. Dinuc

    Dinuc Member

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    It's the distance from the film/sensor plane to the pinhole which for Canon SLRs is about 50mm.

    Dna
     
  8. CeeJay

    CeeJay Member

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    It depends on the camera make , but for a Canon it's 44mm to the flange and about 4mm to 6mm from that to the hole in the cap , depending on whether you make the hole center in the inside or outside of the cap.

    It's about 48mm if the hole is made on the inside (I'd recommend that as it protects the hole from wear, dust .. etc) or about 50mm if made on the outside.


    According to Pinhole Designer 2.0 http://www.pinhole.cz/en/pinholedesigner/ , the optimum hole diameter for that focal length should be 0,309mm
    The angle of view is dependent on the size of the sensor , and for my Canon 400D (22.2mm x 14.8mm sensor - that's a normal 1.6x crop sensor) the angle of view is 31°.
     
    Last edited: Jan 9, 2007
  9. CeeJay

    CeeJay Member

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    Most interesting .. I found this page :
    http://www.bobatkins.com/photography/technical/field_of_view.html
    .. which calculates the field of view and 48mm on a 1.6 crop sensor is a 31° Diagonal Angular FOV , so the focal length on a pinhole non-lens is equivalent to that of a normal lens.

    That means that the 48mm focal length of my pinhole is equivalent to 77mm on a full frame camera.

    The page also mentions pinholes and how the first fisheye lens was a pinhole camera filled with water (because light refracts differently in water of course)
    Almost makes me want to try to make a pinhole non-lens that involves a tube filled with water.
     
  10. CeeJay

    CeeJay Member

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    Since we are on the subject of pinholes , I'd like to ask if anyone knows how to create a zoneplate camera or if they have an pictures of one.
    As far as I understand , you copy the zoneplate pattern on to a medium that allows light to pass through it , so some light is block and some pass through and otherwise it works just like a pinhole .. can someone verify this ?

    BTW if you are making a pinhole cap here is a tip :
    Put a filter in front of the pinhole .. that way the sensor doesn't attract dust , and actually need a UV filter more with a pinhole than you do with a normal lens because an ordinary lens also blocks a fair deal of UV .. a hole blocks nothing ( Which makes interesting for UV and IR photography and in science other kinds of EM radiation imaging as well , like X-ray f.x )

    EDIT:
    Another tip : Full frame camera's (or better yet medium format) give the sharpest images with used with pinholes.
    This is because the circle of confusion on a full frame or medium format sized sensor is larger than on a APS sized sensor.

    BTW I'm wondering if the same isn't true about pictures taken with normal lenses .. are they sharper too on a full frame camera ?
     
    Last edited: Jan 9, 2007
  11. Julz

    Julz Member

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    would the best way to make a hole be to heat up a pin to high temps and stab it thru?
     
  12. CeeJay

    CeeJay Member

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    No. It will make a more clean , round and therefore better hole if it was made in a very thin sheet of metal , than in plastic.

    For my first attempt I tried to see just how well I could make it , by just making the hole in the cap itself.
    I used a drillbit and by hand slowly drilled down until I was almost through, then I used a thin needle to make the hole.
    I then used a much larger drill to remove the rim around the hole , so it would cause vignetting (it would act as a lens hood that was way to long limiting the FOV if I didn't do this.)

    It created an image alright but it wasn't that sharp as you can see.

    For my second attempt I drilled through completely with a 3mm drillbit and then I cut a small piece of aluminium foil and a small piece of an adhesive label my mom (I was with my family for Christmas) uses to label jars.
    I made hole in the label and closed that with the foil and then stuck both onto the bottom of the cap making sure the foil was where the hole in the cap was.
    Then I used a small needle to make the hole in the foil .. that was the second attempt .. much sharper as you can see.

    Update [added pictures]

    Front :
    [​IMG]

    Back :
    [​IMG]
     
    Last edited: Jan 9, 2007

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