snubbr.com

Why do Christmas lights flicker in a viewfinder?
Hello,we've put up a Christmas tree today and I took some pictures with a 40D.When I look through a viewfinder they sort of flicker, certainly are not steady..

They are all steady lights, LED and incandescent, no flicker when looked at with a naked eye..

Viewfinder view is purely optical, mirror, prism and eye-piece..

Does anyone know why the lights would not be steady in a viewfinder?Tks..

Comments (8)

Much the same way stars twinkle but planets don't in the night sky. It's because the viewscreen is not clear but rather slightly frosted. This causes the light from a small source to sometimes hit your eye and sometimes to be bent away from the eye by the small movements of the camera......thus the twinkle.A member of the rabble in good standing..

Comment #1

LM2 wrote:.

Much the same way stars twinkle but planets don't in the night sky.It's because the viewscreen is not clear but rather slightly frosted.This causes the light from a small source to sometimes hit your eyeand sometimes to be bent away from the eye by the small movements ofthe camera......thus the twinkle.A member of the rabble in good standing.

Thank You, makes sense..

They would not twinkle then if camera was mounted on a solid tripod, I'll test that one day...

Comment #2

Marcamera wrote:.

LM2 wrote:.

Much the same way stars twinkle but planets don't in the night sky.It's because the viewscreen is not clear but rather slightly frosted.This causes the light from a small source to sometimes hit your eyeand sometimes to be bent away from the eye by the small movements ofthe camera......thus the twinkle.A member of the rabble in good standing.

Thank You, makes sense.They would not twinkle then if camera was mounted on a solid tripod,I'll test that one day..

They may even twinkle from a tripod as your eye is probably not steady at the viewfinder either. I've not tried that out. I did however confirm your observation that the lights twinkle in a viewfinder.....I'd never noticed it before. Amazing what can be right in front of you and go unnoticed!A member of the rabble in good standing..

Comment #3

Is it the stroboscopic effect?.

Where the refresh rate of your LCD is close to the frequency of the power source driving your Christmas lights. See if you get a scrolling effect when you point your camera at the TV or computer screen..

Cheers..

Comment #4

LM2 wrote:.

Marcamera wrote:.

LM2 wrote:.

Much the same way stars twinkle but planets don't in the night sky.It's because the viewscreen is not clear but rather slightly frosted.This causes the light from a small source to sometimes hit your eyeand sometimes to be bent away from the eye by the small movements ofthe camera......thus the twinkle.A member of the rabble in good standing.

Thank You, makes sense.They would not twinkle then if camera was mounted on a solid tripod,I'll test that one day..

They may even twinkle from a tripod as your eye is probably notsteady at the viewfinder either. I've not tried that out. I didhowever confirm your observation that the lights twinkle in aviewfinder.....I'd never noticed it before. Amazing what can beright in front of you and go unnoticed!.

Yes, a little Christmas tree magic...

Comment #5

While the screen grid is the likely cause here, you may also sometimes notice LED lights flickering at the 60hz electrical frequency. This may be more easily seen at the edges of your vision or if you wave your hand back and forth under their light. Incandescent lights would not have that effect.(just trivia)'Be right, fearless, faithfull, and true to others...'T.S. Elliott..

Comment #6

Booga_roo wrote:.

Incandescent lights would not have that effect.(just trivia).

If they're running on AC current (which most of the civilised world runs on), yes, they do flicker. AC is alternating current, flowing first one way, then the other. The reason we don't usually see any flickering is that the fine tungsten wire in the bulb that generates the actual light doesn't have time to cool down and stop glowing before it gets the next jolt of electricity, which arrives 50 - 60 times a second, depending on your local supply's frequency (Even your local 'base value' varies too, depending on power demand and operational needs - that's one reason why time critical computers, clocks, timers and such are supplied with power through a power filter, which smooths out the supply to EXACTLY what the machine is expecting - just a bit of trivia). Seeing as we can't perceive that 50/60 Hz variation, we consider it a 'steady' light..

LEDs, OTOH, are run ONLY by DC current (unless there's been some major development since last looked), which only flows one way, eliminating any flicker effect. DC powered incandescents, such as you have in your car, are also free from the AC flicker effect. In both cases, poor earth and power connections, or poor supply regulation can lend a simulation of flickering to LEDs. Some LED light packs though, seem to have a built-in on/off cycle that sometimes can be seen. One usage that comes to mind is the truck marker lights that are now often seen on the highway - many of these have a very noticable flicker, possibly to keep the pack cool or to ease the burden on the truck's electrical system - I'll need to investigate this further..

Fluorescent lights are a whole 'nother can o' worms... look 'em up..

Rob.

Everyone, everywhere, has to do everything for a first time. There is no failure in failure, only in failing to learn...

Comment #7

BraveUlysses wrote:.

Booga_roo wrote:.

Incandescent lights would not have that effect.(just trivia).

If they're running on AC current (which most of the civilised worldruns on), yes, they do flicker..

The change in brightness caused by this is imperceptible due to the fact that the filiment does not cool down enough to make a difference. You would be hard pressed to represent this flicker even at higher shutter speeds. If are saying this is what he is seeing through his viewfinder, you've got better vision than anyone I know..

LEDs, OTOH, are run ONLY by DC current (unless there's been somemajor development since last looked), which only flows one way,eliminating any flicker effect..

There has been no great innovation. On cheaper sets(such as the one my landlord got) the lights are completely off during the other half of the 60hz cycle. Hence a flicker can be seen. There is no power supply, and they don't run on DC. Good sets have a capacitor, bridge rectifier, or DC power supply eliminating the flicker..

The ones you see on vehicles are run through the on/off cycle simply to provide different brightnesses for running lights/brake lights so they don't have to put in twice as many LEDs. You may notice little or no flickering when they have the brakes on..

'Be right, fearless, faithfull, and true to others...'T.S. Elliott..

Comment #8

Click Here to View All...

Sponsored Amazon Deals:

1. Get big savings on Amazon warehouse deals.
2. Save up to 70% on Amazon Products.


This question was taken from a support group/message board and re-posted here so others can learn from it.

 

Categories: Home | Diet & Weight Management | Vitamins & Supplements | Herbs & Cleansing |

Sexual Health | Medifast Support | Nutrisystem Support | Medifast Questions |

Web Hosting | Web Hosts | Website Hosting | Hosting |

Web Hosting | GoDaddy | Digital Cameras | Best WebHosts |

Web Hosting FAQ | Web Hosts FAQ | Hosting FAQ | Hosting Group |

Hosting Questions | Camera Tips | Best Cameras To Buy | Best Cameras This Year |

Camera Q-A | Digital Cameras Q-A | Camera Forum | Nov 2010 - Cameras |

Oct 2010 - Cameras | Oct 2010 - DSLRs | Oct 2010 - Camera Tips | Sep 2010 - Cameras |

Sep 2010 - DSLRS | Sep 2010 - Camera Tips | Aug 2010 - Cameras | Aug 2010 - DSLR Tips |

Aug 2010 - Camera Tips | July 2010 - Cameras | July 2010 - Nikon Cameras | July 2010 - Canon Cameras |

July 2010 - Pentax Cameras | Medifast Recipes | Medifast Recipes Tips | Medifast Recipes Strategies |

Medifast Recipes Experiences | Medifast Recipes Group | Medifast Recipes Forum | Medifast Support Strategies |

Medifast Support Experiences |

 

(C) Copyright 2010 All rights reserved.