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mocha has always been very popular as a tracking tool, but with the rising interest in stereo 3D conversion, its rotoscoping capabilities have become a favorite player in that pipeline and sales have soared. In this course, Steve Wright covers the basics of operating mocha, as well as advanced tracking and rotoscoping techniques. The course also covers the mocha/Nuke stereo 3D production pipeline in detail.
When working with log images, you need to do a log-to-linear conversion to make the frames look right in the viewer. So let's see how that's done. I will use the New Project button here. We will choose from our Lesson_ 01_Media folder, the Log Images. Select any frame, click Open. The Color Parameters are on the Advanced Tab. Now, this is a DPX image, you can see that right here. Cineon and DPX images will both be log, and have to be converted to linear.
Now, down here in the Color Parameters is where that's done. Let's look at the Conversion setting here. This is converting bit depth. The default of None means you're not changing the bit depth from the incoming clip. If you select Float, you might do this if you had an 8 or a 16-bit integer image and you wanted to convert it to float in mocha because you were going to do some compositing. You might want to convert a 32-bit float image to 8-bits if you were just doing rotoscoping, because you don't need all that 32-bit floating point precision and 8-bits will get you a little better system performance.
Over here is Colorspace. This is where we tell mocha we want to convert the log image to linear. By default, it's set to Linear which is the typical case for like a TIFF, or a JPEG or a TARGA file. So we'll pop-up the list here and select Log. These parameters down here control the actual conversion from Log to Linear space. The problem is you can't see what you are doing. So we will have to click OK, and then we will go fix it on the Clip Tab, which allows you to modify them. Of course, this looks hideous, so let's go to the Clip Tab and select the Colorspace Tab.
Now, we can adjust all the parameters that convert the log image to linear. Again, we are just doing this so it looks nice in the viewer. So the question is, where do we begin? Well, we can start by setting the Negative Gamma to like 1 and hit Tab key, and that kind of brightens things up. All these other parameters here are in 10- bit log, that is code value of 0 to 1023. The Offset here adds an overall lift or brightening to the picture. If you put-in a code value of 90, that actually brightens the picture by one full stop.
The Log value Reference Black means this code value, code value 95 is going to be pulled down to 0 in the picture. So if I raise this up to a higher number like 200, then code value 200 will be pulled down to black, resulting in a darker picture. We'll put that back to where it was. The Log Reference White is the 10-bit log code value that's going to be pulled to 1.0. So code value 685 out of 1023 is going to be pulled up to white with the default settings.
I change this to a higher number like 800. Now, code value 800 in the log image will be pulled up to white, and the picture will be not as bright. If I lower that value to let's say 600, it was originally 685, if I set it to 600, I am going to bring log code value 600 up to 1.0 in the viewer and the picture will get brighter. Now, I've brighten it up so much that I have introduced clipping. You see how the shirt is all flat, white, blown out.
That's what the Softclip is for. If your log image has specular highlights, very high code values, when you brighten it up to make it look nice, you will get clipping. You can use the Softclip here to help smooth those transitions, so you don't have big, sharp, flat edges. Again, we are dealing with 10-bit log code values of 0 to 1023, so a value like 50 might be a good number to start with. Now you can see we have knocked the clipping out of the picture. So the thing to keep in mind is that all of these conversions are converting the log image to linear color space for the viewer, so it looks nice for you.
It has no effect on the original image. The last thing we should look at right here is this Linear button. As I said before, this is typical for your TARGAs, your TIFFs, and your JPEGs. This Video Gamma down here can be used to brighten them up or darken them down. The difference between this Video Gamma and the one up here is this one up here is to temporarily make the viewer brighter or darker, so you can see parts of the picture better. It's temporary, so you can turn it on and off when you need.
The Video Gamma down here is designed to be a global gamma correction to make the entire clip look nice. You will definitely want to convert your log images to linear, because leaving them log, they have such low contrast that it makes it hard to see what you are doing.
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