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View Full Version : Color Correction. What exactly is it and why is it necessary?



Farhad_azer
04-09-2017, 10:17 AM
Hi there,
I know my question is not related to lw3d but i would be very happy to know more about it.
I only have rough idea based on its name. In fusion there are some bottons and tools.
A film maker has asked me to work on it.
Any help would be greatly appretiated.

Sensei
04-09-2017, 10:21 AM
https://en.wikipedia.org/wiki/Color_correction

https://en.wikipedia.org/wiki/SRGB

TheLexx
04-09-2017, 02:08 PM
My understanding is that there are two colour corrections - Primary and Secondary.

Primary colour correction is making sure that the main colours balance, for example to make sure there is not a green tinge or a blue tinge to the picture. Also the black levels and white levels are checked to see the picture is not too dark or too light above or below the levels.

Secondary colour correction is when you want to achieve a specific artistic look so you would deliberately start to adjust the colours in that direction form the dark areas or the light areas or the mid-tones. For example, for a horror film you might want to deliberately make the shadows darker, or for a romance you might want to deliberately bring out a happy orange colour in some areas of the picture.

Three things:-
1) To grade a picture it is nice to have a good codec and bit-rate to work with otherwise the colours could break apart during grading - so 10-bit uncompressed images are generally considered better than 8-bit heavily compressed images.

2) You have to have some idea of the official colour standards you are working for - a film intended for a digital cinema projection will have a different output colour profile to a film intended for HD broadcast TV. These profiles define what start and finish levels you are allowed for white, black and the red/green/blue primary colours. One standard can be converted from one to another, but it is generally a good idea to start work with a higher quality and output down to a lower quality than start with a low quality and try to magically output a higher quality. As you can imagine, something like a cinema film will have a much higher specification than something like a standard definition dvd.

3) For colour grading, not all monitors are built equal, so do not expect to colour grade on a cheap $200 computer monitor. Some companies will happily spend $50,000 on a grading monitor, but luckily there are better options now than there used to be, but around $1000 or over (make sure you check what specific colour profiles the monitor can handle). It is vital a monitor is calibrated before you start using it for colour grading - this makes sure that what you see on your screen is exactly the same as another professional will see on his/her screen (remember they could be on the other side of the world so this is important as you work towards the finished product). From memory, some Eizo models are self-calibrating.

Overall it's a can of worms, but if you can define your own workflow and control the budget, you should be okay. If anyone else can chip in to either correct (no pun intended !) or add, it would be great to get any wisdom on how anyone works.

TheLexx
04-09-2017, 02:28 PM
One thing I didn't mention was compositing - if the mad robot you have made in Lightwave needs to run down the real road which you have filmed on your DSLR, then you will need to colour grade to match the footage, so the audience can believe the robot really is running down the road, if you get the idea. Good luck !

MonroePoteet
04-09-2017, 05:06 PM
When filming, most good digital cameras have what is called "White Balance". This allows you to set the internal camera color correction to adjust for the ambient lighting. Most white balance implementations have presets for Sunlight, Cloudy, Tungsten lamp, Fluorescent lamp, etc. each of which "warm up" (i.e. more yellow) or "cool down" (i.e. more blue) the captured images to adjust for the ambient lighting to make White things actually look White, with the other colors being corrected accordingly. They also usualy have a "Sample" setting which allows you to put something that is actually White in front of the camera, press a button to sample it and adjust the camera's color correction for the ambient lighting to make that White. I carry around a small piece of white polystyrene in my camera pouch for doing white balance, or you can buy an "official" standard white / grey balance card from a photo supply shop.

If you *don't* do White Balance in the camera, then the footage shot may be "off", and need to be corrected unless that's the artistic feel the production designer or art director wants. For example, I was filming a friend's model railroad in their living room, but forgot to do a White Balance and ended up with very yellow-ish footage from the diffuse sunlight coming in the front window which I corrected in the NLE (non-linear editor). Another example is I was filming birds in the sky at various times and wanted the final production to fade between the shots, but the sky was more bluish / greenish / turquoise in the various shots, so I color corrected them to be the same hue in the NLE.

As TheLexx mentioned, there's also *artistic* color correction, but it also usually involves gamma correction (how dark the darks are relative to the rest of the light curve), light / contrast of the full frame, saturation of the color space, etc. Lightwave provides a number of output buffers which can be captured (using the Compositing Buffer Export Image Processing plugin) and used to do enhancements of the CGI footage for matching live footage.

mTp

erikals
04-09-2017, 05:21 PM
because >


https://vimeo.com/8200251