Posted by Han on March 28, 2003, 4:05 am I used it to correct some evening recordings that appeared just too blue or green. To get a better white balance I tried playing around with the sliders of the colorization filter but found it hard to get correct values and very time consuming! I then tried a different approach, as described below. Basic idea: For me it worked fine to correct a few clips with a green or blue flare in this way. You can use any freeware color picker tool or use the one present in some Premiere filters. To get a color picker inside Premiere apply the Premiere Color Replacer filter (temporarily) to some (other) clip on the timeline and select this clip. Now scrub to the desired frame in another clip on the timeline you want to correct and select the picker icon from the filter to pick the color of a pixel in the desired area on the monitor window. Double click on the color picked in the filter settings and read the RGB values. Afterwards delete the Color Replacer filter. I would like you to comment on this. It shouldn't be too hard to create a small program to do the maths or for Matrox to implement such a color picker+maths behind an extra auto-white balance button in the colorization filter in a way similar to the much more sophisticated one found in RT.X100. H.
145.7.200.27
Hi all,
I have tried the following to calculate correction values for the Matrox Colorization video filter to have a semi real time white balance function on RT2xxx. It works pretty well for me.
- Use a color picker to pick the current color of a pixel in part of your clip which should be white, but isn't. Make sure not to pick an under- or overexposed area of the clip.
- Calculate correction settings for the real time Colorization video filter to adjust this to pure white, doing some simple maths shown later.
- Enter these settings in the Matrox Colorization video filter.
- Ready: white is now white as is should be. Also the overall clip brightness seems still the same.
Detailed steps:
1. Scrub to a frame in your clip on the timeline which has some area in it which should be white, but isn't.
2. Use a color picker to determine the RGB settings for a pixel in this area from the monitor window. Let's say for example it is a bit too blue and gives R=200,G=200, B=230.
3. Now calculate the average value: A=(R+G+B)/3 For the example values this gives A=(200+200+230)/3=210
4. Calculate the correction value for red=A/R, green=A/G and blue=A/B. For the example values this gives 210/200=1.05, 210/200=1.05 and 210/230=0.91. As percentages: 105%,105%,91%.
5. Now apply a Matrox colorization Video Filter to the clip, select Dud effect, and then under Custom Settings you can enter the calculated color values as percentages. Make sure you slide the key frame slider to the left side before making your settings or it will only affect 1/2 of your clip. There are 2 sets of RGB controls, make sure you use the set to the LEFT!
6. The white in you clip is now really pure white and the overall brightness of the clip is still the same.
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