Color shift on SONY DSR500
Posted 02 November 2005 - 08:41 PM
Posted 02 November 2005 - 09:06 PM
You see, when you make a balance the color temp value that appears in the VF is very unprecise, and, more than that, it won't tell you what correction is made on the green channel.
Color temp itself is based on the relative B/R values, but the balance is actually made on the 3 channels.
Having the information of a 3200 K temp when you make a balance doesn't mean your light matches the preset values, that are the ones of a standard 3200 K light with no green or magenta shift.
The first questions that come to my mind as to try todetermine if your camera has a problem would be :
- Are you sure you made this test and found this problem in a regular 3200 K Tungsten light (new bulbs, correct power, no cast due to reflections on the set, no neon bulbs not discharge lamp of any kind (they have green / magenta unregular casts)
- Does the preset value give you a good image in regular 3200 K tungsten light ?
- Does the white balance give you a good image anyway (even though it's a bit different from the preset) ?
- Is the image better in the preset position or when you do the manual white balance ?
- Do you have the same problem in every different filter position ?
- Is the cast mainly visible in highlights or does it affect especially the shadows ? If so, make a black level balance before the white balance, check that the iris fully closes to the 'cap' position when black level is operating, if not, give it an help closing properly when the automatic shutter tries to go to the capped position
- mind that the values manually computed are not necessarly reseted by the menu reset, esp. the white balance manual settings...
- Do you have a waveform/vectorscope ? if so, check on a white card what position is the best
Posted 03 November 2005 - 11:51 PM
Thanks for your help. I love the cinematic movies you have done with dvcpro. Which model camera do you use?
Posted 04 November 2005 - 05:14 AM
So it's not easy to say if your different problems are actually related to one only or if it's more complicated than this. I would not take too much a valuable conclusion from what happens in such weird/special light as a stadium lighting. Who know if they changed the bulbs recently, or if the electrical power asn't changed for anyspecial reason etc.
Do your test under known conditions, anyhow.
Check your reset value and your monitor as well...
If you still notice the problem, I'm afraid you should give it a full check-up, as far as I know...
Off-topic : The work you refer to is only a student job that I coached (students don't drect, only do the technical jobs). We used AJD 610 Panasonic DVCPRO 25, and Philips LDK 140 DVCPRO 50, basically.