Why Does Camera Flash Brighten Stars in the Sky?

Click For Summary

Discussion Overview

The discussion revolves around the phenomenon observed when using a camera flash while photographing the night sky, specifically addressing why stars appear to brighten in the image. Participants explore the implications of this observation, considering both the physical properties of light and the mechanics of human perception.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant claims that using a camera flash brightens the stars in the sky, questioning the underlying reason for this effect.
  • Several participants challenge this claim, asserting that the flash does not actually brighten the stars.
  • Another participant suggests that the perceived brightening may be an illusion rather than a physical change in the stars' brightness.
  • A detailed explanation is provided regarding the mechanics of photographic film and human vision, proposing that backscatter from the flash may enhance the perceived contrast of stars without actually increasing their brightness.
  • There is a request for photographic evidence to support the initial claim, indicating a desire for empirical validation.

Areas of Agreement / Disagreement

Participants generally disagree on whether the camera flash actually brightens the stars, with some asserting it does not and others maintaining that it appears to do so. The discussion remains unresolved regarding the nature of the observed phenomenon.

Contextual Notes

Participants express uncertainty about the mechanisms of perception and the effects of photographic techniques, with some assumptions about the nature of light and vision remaining unexamined.

apeman2001
Messages
3
Reaction score
0
When I point a camera at the sky and use the flash, it brightens up all the stars I'm looking at (not just the ones on the screen). Does anybody know why this is?
 
Astronomy news on Phys.org
russ_watters said:
Welcome to PF...

No, it doesn't.

Have you tried it?
 
apeman2001 said:
Have you tried it?

No. Can you post sample pics?
 
russ_watters said:
No. Can you post sample pics?

If I post a picture, it will just look like a picture of the night sky. I'm trying to say that when I take a picture with flash, I can see several stars that the camera is pointed at become brighter for a second. It doesn't make any sense to me because all of those stars are many light-years away.
 
Black and white photo emulsions consists of grains of silver iodide in an organic matrix. To develop a photograph each grain of silver iodide must absorb a multiple number of light quanta before it becomes unstable and decomposes the translucent grain into silver. (The larger the grain, the more quanta are required.) When this happens the grain explodes leaving a small black spot of finely dispersed silver.

The larger the "grain"-- a single crystal of silver iodide actually--the more electromagnetic quanta are required to make it disassociate. But some clever fool discovered that he could sensitize film by pre-exposing it in a bath of low intensity light. After this is done the number of photons required to hit the explosion threshold for a crystal of SI is lowered; it requires fewer photons to cause the crystal to explode and put a spot on the film.

[btw, this is called pre exposed film.]

Your eyes works in the same fashion. It takes multiple photons to trigger a rod or cone to send a neural impulse to your brain.

It is possible that the back scatter from the flash, trips the photon count threshold on the retinal image where the stars are projected onto your retina, but is sufficiently weak that the critical threshold, where there are no stars, is not reached. So for a brief fraction of a second you could perceive better contrast of a star field.

Or are you looking at an enhanced image on a monitor?
 
Last edited:

Similar threads

High School How bright is the Sun compared to the sky?
  • · Replies 17 ·
Replies
17
Views
4K
Stargazing Can Stars Be Spaghettified in a Matter of Days by Black Holes?
  • · Replies 17 ·
Replies
17
Views
3K
High School What Are the Mysterious Zig Zagging 'Stars' in the Night Sky?
  • · Replies 5 ·
Replies
5
Views
5K
High School Can nature do this in the night sky?
  • · Replies 5 ·
Replies
5
Views
2K
High School Night Sky of Alpha Centauri: Sol as a Bright Star
  • · Replies 15 ·
Replies
15
Views
4K
Undergrad A busy and interesting night sky in Mackinaw City
  • · Replies 1 ·
Replies
1
Views
2K
High School Star like object travels in a zigzagging pattern relative to other stars
  • · Replies 49 ·
2
Replies
49
Views
12K
Stargazing What Is This Strange Light in the Night Sky?
  • · Replies 12 ·
Replies
12
Views
5K
High School How can the Universe be flat? Ridiculous
  • · Replies 13 ·
Replies
13
Views
5K
Undergrad Lines of stars that we see in the sky
  • · Replies 26 ·
Replies
26
Views
6K