Formulas for camera obscura (correct sub forum?)

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SUMMARY

The discussion centers on setting up a military surplus command tent as a camera obscura for observing a solar eclipse. The main challenge is determining the correct focal length relative to the hole diameter for optimal image quality. A rule of thumb states that the hole diameter should be 1/100th of the distance from the hole to the image screen, as referenced from cameraobscuras.com. Additionally, participants highlight the importance of managing exposure times due to low light conditions during the eclipse, suggesting automated digital photography for better results.

PREREQUISITES
  • Understanding of camera obscura principles
  • Basic knowledge of focal length and aperture concepts
  • Familiarity with exposure settings in photography
  • Awareness of light sensitivity in film and digital cameras
NEXT STEPS
  • Research the mathematics behind focal length and aperture size
  • Learn about low light photography techniques and reciprocity failure
  • Explore automated digital photography settings for eclipse events
  • Investigate local astronomy clubs for eclipse viewing tips and resources
USEFUL FOR

Astronomy enthusiasts, photographers planning to capture solar eclipses, and educators seeking practical demonstrations of optical principles.

Ravensong
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Experiment / demonstration: Set up military surplus command tent as camera obscura / pinhole projector for observation of full soar eclipse.

Problem: lacking in personal knowledge of the formula needed to determine correct focal length to hole diameter

Solution: Request assistance from actual scientists instead of Brittanica and Wikipedia

Thank you in advance for the help, I'll no doubt have further related questions on this project as I start attempting to do the maths.
 
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The main driver of the size of the hole is the amount of light you will need, not so much the focus. Larger holes reduce the focus unless the hole is so small that optical effects blur it. The rule of thumb given in http://www.cameraobscuras.com/camera-obscura/faq/ is that the hole diameter should be 1/100th the distance from the hole to the image screen.
 
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TYVM, love the link!

Any warnings / advice on getting good photos & film of the event? (mostly wondering if the lower light levels will mess with photo quality)
 
Film can be sensitive to low light reciprocity error, where the exposure time has to be longer than the normal calculation. It happens fast and changes from full sunlight to night, so it would be tricky. Automated digital photography is probably easier.

PS. I attended a meeting of the Fort Worth Astronomical Society where they were planning their trips. Someone here can probably give you a reference in your area. One of the recommendations from some avid eclipse chasers was to minimize the photography (or don't do any) during your first eclipse and just absorb the atmosphere. Apparently, it is very spooky and memorable. Save the photography for later eclipses.
 

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