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Old Feb 13, 2005, 10:39 AM   #11
NHL
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FYI - http://www.fredmiranda.com/forum/topic/176196

-> ie white balance and AE lock will not work!
... more powerful flashes (may be ceiling mounted professional strobes :G) - or RAW: http://www.rawworkflow.com/forum/arc...hp/t-6615.html
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Old Feb 13, 2005, 11:07 AM   #12
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the answer to the light level issueare the sodium vapor lights cycle. depending on the type and manufacturer at 60Hz. as it goes up and down the sine curve it changes level and color. we don't see it but shooting above the 1/60 timing will make it quite apparent.
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Old Feb 13, 2005, 11:21 PM   #13
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SJMS is 100% correct ...... you would need a faster shutter speed to get more consistent results but then you would have dark images lol.... youd need a good flash with a relatively high guide number.... sigma super dg would help a bit however the cycle time between shots would kill your fps if you need bursts....
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Old Feb 13, 2005, 11:55 PM   #14
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That 60 cycle thing makes perfect sense. At first look I noticed the differences in color temp but when I looked again I could see that there are different exposure levels as well.

Talk about amoving target!

Seems to me that Sodium Vapor are the white ones and Mercury Vapor are the pink ones - right? Do they both pulse like that? I think they both use a ballast.

and welcome to the forum acrabb!
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Old Feb 14, 2005, 12:02 AM   #15
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Amateur: sodium vapor are generally more yellow in tone, mercury vapor are more blue in cast... and another type is metal halide which are sometimes ina variety called HQI which are color regulated and have a very "sun" like warm color .. still lot of yellow but much more natural then the other 2. All use ballasts to ignite them ... around 10,000 -25,000 Volts to fire them up... basically the same technology in car HID headlamps.
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Old Feb 14, 2005, 3:02 AM   #16
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I get it now, thanks mrkryz
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Old Feb 14, 2005, 3:29 AM   #17
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Vapor based lamps:

Heat the lampand includedmetal until it'svaporized. Force a small electric current through to ionize the metal vapor. Ta-da. Light!

The color is the spectrum of that particular element. Mercury, blue white; sodium, warm yellow; etc. Also why color balance under these types of lights is impossible.

The lamps respond to the AC they are powered from. Thus they blink on and off 60 times a second here in North America, 50Hz in most other locales. Our eyes average the light, but the camera can't,and will see dark or light unless an exposure includes one full cycle of the lamp (1/30 or slower shutter speed is best). If there are two types of lights nearby, the colors will shift as one type may dim quicker than the other. Color is a problem if incandescent lamps are also nearby - these stay warm and thus average out so you can photograph under them, but aren't nearly as bright as vapor lights - thus the vapor color will win.

Manual white balance: I find daylight works best because teh final exposure will be most "slidelike". Autoexpose, but use Tv and set ashutter at 1/30 second and hold very steady when shooting. Or try 1/15 or 1/8 and use a tripod.






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Old Feb 14, 2005, 1:14 PM   #18
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Unfortunately what you are experiencing is "normal" for the situation, very frustrating, but normal.

Follow everyones advice - and get totally confused.
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