pulse problem at DVinfo.net

Rocco Lobosco · July 18th, 2007, 05:10 AM

When i shoot with high shutter (500-1000) i've seen a strange pulse of white balance and iris, colorimetry an luminosity change randomly white a pulse effect...
the problem occour with 2 cameras (both rent from same store )and i've see it on a studio monitor.
maybe a defective series?
obviously white balance and iris is set to manual, indoor shoot and illumination with arri 1200 and 575.
Anione have this problem? ideas of this electronic strange behaviour?

thanks and excuse me for my english :)

Don Palomaki · July 18th, 2007, 11:10 AM

Using high shutter speed with discharge lamps can result in variations of white balance and perhaps exposure. This is because at high shutter speed, the CCD is seeing only a small portion of the lamp output over the power cycle (perhaps 15% of it, or less, at 1/1000), and that portion may have a color and brightness that is different from the average output of the lamp over the full cycle, especially near the start/end of the power pulse. The effect will be much more pronounced with standard magnetic ballasts.

Try reducing shutter speed until the undesired effect goes away. If you must use the high shutter speeds to freeze motion, try use a different type of lighting with more continuous output.

Rocco Lobosco · July 18th, 2007, 12:50 PM

thanks a lot for hint don :)

July 18th, 2007, 05:10 AM	#1
Rocco Lobosco New Boot Join Date: Jul 2007 Location: Italy Posts: 3	pulse problem When i shoot with high shutter (500-1000) i've seen a strange pulse of white balance and iris, colorimetry an luminosity change randomly white a pulse effect... the problem occour with 2 cameras (both rent from same store )and i've see it on a studio monitor. maybe a defective series? obviously white balance and iris is set to manual, indoor shoot and illumination with arri 1200 and 575. Anione have this problem? ideas of this electronic strange behaviour? thanks and excuse me for my english :)

July 18th, 2007, 11:10 AM	#2
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,487	Using high shutter speed with discharge lamps can result in variations of white balance and perhaps exposure. This is because at high shutter speed, the CCD is seeing only a small portion of the lamp output over the power cycle (perhaps 15% of it, or less, at 1/1000), and that portion may have a color and brightness that is different from the average output of the lamp over the full cycle, especially near the start/end of the power pulse. The effect will be much more pronounced with standard magnetic ballasts. Try reducing shutter speed until the undesired effect goes away. If you must use the high shutter speeds to freeze motion, try use a different type of lighting with more continuous output. __________________ dpalomaki@dspalomaki.com

July 18th, 2007, 12:50 PM	#3
Rocco Lobosco New Boot Join Date: Jul 2007 Location: Italy Posts: 3	thanks a lot for hint don :)