How Does A Camera Work Science Fair

Digital Pinhole Camera

Abstruse

If you sit under a leafy tree on a sunny day, y'all may notice spots of sunlight on the ground from light passing through spaces between the leaves. Try putting a piece of paper-thin on the ground and examining the spots of lite on the paper-thin. Even though the spaces through which the low-cal is passing are irregular in shape, the spots on the cardboard are round. What you are seeing, in fact, are projected images of the sun. Light passing through an aperture forms an epitome. A pinhole photographic camera uses a tiny discontinuity, instead of a fancy lens, to project an image. What happens to the quality of the flick as the size of the pinhole is changed? This projection shows y'all how to observe out.

Summary

Average (6-x days)

Must have digital photographic camera capable of taking long, controlled exposures without flash.

Readily available

Very Low (under $20)

No issues

Andrew Olson, Ph.D., Science Buddies

Sources

• Hanft, A., 2005. Pinhole Camera (office 3), Be A Blueprint Grouping Blog. Retrieved Apr three, 2006.

Objective

The goal of this projection is to measure the resolution of a pinhole camera every bit a function of pinhole diameter.

Introduction

Light passing through an aperture forms an image. Sunlight passing through spaces between the leaves on a tree projects an image of the dominicus. Brand a loose fist with your hand on a sunny day and y'all can projection an paradigm of the sun through the aperture that your fingers make. For a great introduction to light and apertures, including many interesting demonstrations you tin practice yourself, see Bob Miller's "Light Walk" pages, in the Bibliography section (Miller, date unknown).

The resolution of the image projected from an aperture is determined by the size of the aperture (until the discontinuity becomes and so small-scale that diffraction of lite dominates). Thus, the smaller the aperture, the greater the resolution of the image. When the size of the discontinuity approaches the wavelength of the light passing through it (roughly 400–750 nm for visible light) diffraction of the low-cal by the aperture limits the resolution.

In this project, you volition build a digital pinhole photographic camera. You'll make several different-sized pinhole apertures for your camera, and you'll measure the camera's resolution as a office of aperture size. You can build a pinhole camera for pic, but loading and unloading the film has to be done in full darkness. Also, you lot take to take the pic processed before y'all can see the results. Determining the correct exposure time for a pinhole photographic camera often involves some trial and error, and this tin can apace become dull when using moving picture. A big reward of using a digital camera is that yous tin see your results correct away.

Since a pinhole does not allow in much light, exposure times will be much longer for a pinhole photographic camera than for a camera with a normal lens. Therefore, you must apply a digital camera that provides a method for decision-making long exposures (due east.g., via a remote-control cable). For the lightbox photographic camera described, exposure times may need to be tens of seconds, or fifty-fifty a minute.

In that location are two ways to brand a pinhole photographic camera with a digital camera. Which method y'all use depends on the type of digital camera you take. If your digital camera does have removeable lenses, y'all can make a pinhole for it using a spare trunk cap with a pinhole in place of the lens. With this type of camera, the light coming through the pinhole aperture forms an epitome directly on the lite-sensitive component within the camera.

If your digital camera does non have removeable lenses, you will utilize the "lightbox" (or camera obscura) method. With the lightbox, the pinhole projects an image onto a screen at the back of the box. Your camera takes a picture of this screen, through a small, light-tight "window" at the front of the box (see Effigy ane).

With this type of camera, the exposures are even longer than typical pinhole cameras, considering the lite from the pinhole does not autumn direct on the light-sensitive region of the camera. Instead, the camera is capturing some of the lite that is reflected from the projection screen. This, in plough, is only a fraction of the light that originally passed through the pinhole.

The resolution of the image will be determined by how much the light is "spread out" as information technology is projected through the pinhole. With larger pinholes, this will be determined by the bore of the aperture. As the pinholes become smaller, diffraction will brainstorm to take a significant effect. Diffraction ultimately limits the resolution of an optical system, even something as simple as a pinhole.

Terms and Concepts

To do this projection, yous should do inquiry that enables you lot to empathize the post-obit terms and concepts:

• Discontinuity
• Diffraction

Questions

• How minor does the pinhole take to be before diffraction becomes dominant in determining resolution?

Bibliography

• The post-obit sites have useful information on pinhole cameras, including making pinholes, calculating exposure times, and calculating dimensions for building cameras:
  
  • Balihar, D., 2006. Pinhole Photographic camera: Photographs, Information, PinholeDesigner, Pinhole.cz. Retrieved April 3, 2006.
  • MrPinhole, date unknown. Pinhole Photography and Camera Design Calculators,. Retrieved Apr iii, 2006.
• This webpage has specific data on building a lightbox-blazon digital pinhole photographic camera:
  Hanft, A., 2005. Pinhole Camera (part 3), Exist A Blueprint Group Blog. Retrieved April 3, 2006.
• Bob Miller has created many exhibits at the Exploratorium in San Francisco built effectually light projected through apertures. If you tin't visit Bob'south exhibits at the Exploratorium, you can still visit his Light Walk pages online. They are a good intuitive introduction to pinhole optics. Yous can also larn how to make your own pinhole viewer.
  Miller, B., appointment unknown. "Bob Miller's Calorie-free Walk," Exploratorium. Retrieved April 3, 2006.
• Diffraction and the limit of resolution in photography:
  McHugh, South.T., date unknown. Tutorials: Diffraction and Photography, Cambridge in Color. Retrieved April 4, 2006.

Measuring Resolution

• This is a less detailed ready of instructions:
  Doty, J., 2000. Lens Testing with the USAF 1951 Chart, JimDoty.com. Retrieved April 4, 2006.
• Norman Koren's site as well provides relevant information:
  Koren, Due north., 2005. Agreement Image Sharpness, Function 5: Lens Testing, Norman Koren Photography Page. Retrieved Apr 4, 2006.

Measuring Sharpness: The Modulation Transfer Role (MTF)

• A good, basic description of the gold standard for measuring sharpness, the modulation transfer office or MTF:
  Atkins, B., 2005. MTF and SQF, Bob Atkins Photography. Retrieved April 4, 2006.
• How to actually mensurate MTF for a lens:
  Koren, North., 2005. Understanding Image Sharpness, Function 5: Lens Testing, Norman Koren Photography Page. Retrieved April 4, 2006.

Materials and Equipment

• Flat blackness paint
• Scissors or a hobby knife
• Soda can
• Tin snips
• Needle
• Bit wood (a few pieces)
• Sandpaper, fibroid and fine
• Digital camera. It must be able to take long, controlled exposures without flash.
  • If y'all are using a digital camera that has removeable lenses (i.e., a digital single lens reflex [DSLR, or SLR] camera), you lot will as well demand:
    • Spare body caps (at least 3). Y'all should exist able to order these from the photographic camera store where you purchased the camera. Y'all volition make a pinhole for the camera using a spare body cap with a pinhole in place of the lens.
    • Drill
    • Glue
    • Black tape
  • If you are using a digital camera that does not have removeable lenses, yous will use the "lightbox" (or camera obscura) method. To make a lightbox, you volition too need:
    • A box
    • Aluminum tape
    • Condom from bicycle inner tube
• Optional: Photo editing software will exist useful for analyzing results.
• Lab notebook

Experimental Procedure

1. The analogy shows an example of a lightbox-type pinhole photographic camera, suitable for use with a digital photographic camera (Hanft, 2005).
2. Here are some tips on amalgam a lightbox-type photographic camera (for more details, see Hanft, 2005):
   1. The box depth is determined by how shut your camera tin focus. The farther your projection screen is from the pinhole, the dimmer the light volition be, and the longer exposures you'll have to take, then endeavour to go on this reasonably short (x-12 inches, if possible).
   2. Paint the inside of the box flat blackness to preclude devious reflections. This is particularly important with the long exposures you'll be using.
   3. Cover the outside of the box entirely with aluminum tape, to ensure that your box is lite-tight.
   4. For the "window" for your digital camera, use a piece of rubber tubing from an old bicycle inner tube to make a tight-fitting rubber seal that will fit effectually the lens of your camera. This volition perform two functions: 1) brand a lite-tight seal, and ii) agree the camera firmly in place.
   5. Also, remember that the camera needs to be tilted down slightly so that information technology does not block light entering the pinhole (encounter Effigy 1 in the Introduction).
3. Turning a digital SLR photographic camera into a pinhole camera is much easier. All you lot need are some spare body caps, which you should exist able to order from the camera store where you purchased the camera. Notice the center of the body cap and drill a pigsty in it. Glue a pinhole made from thin aluminum, over this pigsty, and brand the glue joint low-cal-tight by covering it with black tape.
4. Here are some tips on making and measuring a pinhole (used for either type of photographic camera:
   1. Here are instructions for making a pinhole from David Balihar: "A piece of metal cut from a drinks [soda] can, approximately four x four cm, is sufficient. Get-go, using fibroid sandpaper, remove the paint from the expanse where the hole should exist, and attempt to brand the metal as thin as possible. Then finish the surface by using fine sandpaper. Identify the plate on a flat wooden block and, using a abrupt needle, make the smallest hole possible. Exist careful not to injure your mitt and use a difficult block to press down on the needle. Remove the embossed material from the contrary side of the plate using fine sandpaper. Identify the needle into the hole over again and, past gently pressing and turning the needle between your fingers, make the pigsty round. Smooth the hole again using sandpaper. It is necessary to repeat the process until the required diameter is accomplished. A regular circular hole in a very thin plate can exist made with a bit of patience." (Balihar, 2006) Use the same size for each of the aluminum pieces, and then that your pinholes are hands interchangeable on your photographic camera.
   2. Remember to paint the back side of the pinhole metal flat blackness after yous have made the pinhole. The dorsum side volition be inside the camera, and y'all want to prevent stray reflections inside the camera.
   3. In that location are many means to measure the bore of your pinholes. You can use a alide projector, overhead projector, or enlarger to project light through the pinhole, and measure out the bore of the enlarged epitome. To check the scale (enlargement factor) as well mensurate the projected size of the edge of the aluminum. Another method is to use a flatbed scanner at 600 or 1200 dpi.
5. Make a set of at to the lowest degree iii dissimilar pinholes (more than is even ameliorate) for your photographic camera spanning a range of diameters from about 1.0 mm to 0.2 mm (or less).
6. Experiment with exposure times so that yous tin can photograph the same scene with each different pinhole to achieve about equal grey levels in the photographs. (The references in the Bibliography take data and calculators that should help with this. Knowing the diameters of your pinholes will also aid.)
7. If yous are using a lightbox-blazon camera, it is best to keep the discontinuity setting constant, and change only the exposure time.
8. Go on the camera steady past attaching it firmly to something heavy (eastward.one thousand., a brick).
9. The Bibliography has references that will show y'all how to quantify both resolution and sharpness for your photographs made with different-sized pinholes.
10. Here are some questions y'all can attempt to reply with your pinhole camera.
    • What pinhole diameter maximizes resolution for your camera?
    • What pinhole diameter maximizes sharpness for your camera?
    • How practise these compare to the predicted results from the pinhole calculators in the Bibliography? If in that location are differences, can you explain them?

Ask an Expert

Practice you have specific questions nigh your scientific discipline project? Our squad of volunteer scientists can help. Our Experts won't practice the work for yous, but they will make suggestions, offer guidance, and help y'all troubleshoot.

Variations

• How does resolution with a pinhole compare to resolution with a normal photographic camera lens?
• How does depth-of-field with a pinhole compare to depth-of-field with a normal photographic camera lens?
• How does sharpness with a pinhole camera compare to sharpness with a normal camera lens?
• Examine exposure time in relation to pinhole size. Call back to continue digital photographic camera discontinuity constant for lightbox-type camera. Apply photo editing software and conform exposure time to match gray values in the images taken with different-sized pinholes.

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MLA Style

Science Buddies Staff. "Digital Pinhole Camera." Science Buddies, xx Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Photo_p005/photography-video/digital-pinhole-camera. Accessed 12 June 2022.

APA Style

Science Buddies Staff. (2020, November 20). Digital Pinhole Camera. Retrieved from https://www.sciencebuddies.org/scientific discipline-fair-projects/project-ideas/Photo_p005/photography-video/digital-pinhole-camera

Last edit date: 2020-11-xx

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