How can I photograph light coming through a keyhole more effectively?
Asked 5/20/2015
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2 answers
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I’m making an art photograph where light shines through a door’s keyhole and is photographed on the other side along with the lock and a nearby object. The visible light coming through the keyhole is very weak. Is there any practical way to increase or “amplify” the light through the keyhole, or is there a better photographic approach?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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The easiest answer is "time". You don't need to amplify anything: you just need to collect it for longer. The overall exposure of your photo is the amount of ambient light that is accepted through the camera's aperture for the amount of time the shutter is open.
Presuming that your object doesn't move, simply take either one long exposure or a sequence of shorter ones and combine them together.
Otherwise, you could use some sort of lens to collect more light to send through the keyhole (on the outside, not the inside). A focusing mirror system (not a flat mirror) could also help here. How to do that might be better handled by the people over on https://physics.stackexchange.com/. But this is also not amplifying it, really — it's just making sure that less of it is wasted by hitting the door. And, my strong intuition is that either one isn't really going to be a significant difference, and especially not at any reasonable cost.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
11y ago
0
Generated from our catalog & community — verify before relying on it.
You generally can’t “amplify” light with a mirror or simple optics; you can only direct more of the source light through the keyhole more efficiently. For photography, the simplest solution is usually to collect the weak light longer: use a long exposure, or shoot multiple shorter exposures and combine them, as long as the scene stays still.
If you want more light through the keyhole itself, improve how the source is aimed and concentrated before it reaches the hole. A focusing reflector or parabolic mirror can help send more of the LED’s output toward the opening, reducing wasted light. A lens may also help gather and direct light, depending on the effect you want.
Your final result will depend on the full exposure triangle: aperture, shutter speed, and ISO. In practice, experiment with exposure length, camera sensitivity, and how tightly the light is directed at the keyhole. If the scene is static, longer exposure is usually the easiest and most reliable fix.
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