Author: Vitus Lasrado

The class was started by Gonzalo explaining the importance of regrain in your plate and how to work with them. We saw 3 different alternatives. The first one was to use the minus the original plate and the denoise. The second way is to use a regrain node. The third way was to use a new gizmo and this was now the standard in the industry, it’s called DasGrain.

Patching was the next thing we learnt. We had learnt how to fix the patch and cover them up, but it was on a balanced light this class was about how to cover them up with uneven lighting. We saw different ways to tackle it. High and low-frequency, image frequency separation help to preserve details and later reuse the details during cleaning. To get the low frequency we use blur and to get the high frequency we use from, then use plus to marge them. 

The next method was similar, but this time we used the divide and multiply, we use only one roto paint and we can use the blur to control the light.

The final method was to track the point you want to patch, then use blur for the premult and the patch and then divide them, and then multiply with the patch. Later grain the back and over it with the plate. This way the patch will move with the track and the light will move with it.

The curve tool helps to match fluctuating colours or remove a fluctuation, what I mean by fluctuation is any kind of light. How this tool works is, first to select the region to match, this could be the whole frame or a part by rotoing it. Then hit the ‘GO” button to analyse the range. Next copy the Maximum and Minimum Luminescence Pixel Value and paste it into the Grade lift and gain. Then added Grade to the plate which has to match the light.

The next way we saw how to clean up the patch was easier and quicker. First roto around the marker, then transform and move the plate a little bit so you can hide the marker. Tack the point and past the value to the roto. Oremult and merge over the original plate.

The next method is the same as the before one, but in this, we use roto paint to do the patchwork and roto around the marker we need an alpha to cut out the region with which we cloned. 

InPaint is the best way to work on patch removal. First roto the area you want to patch and track it. Matte to InPanit and make sure it is on Matte Aplha then adjust the setting. Added the grain to the patch, copy the alpha of the patch to the alpha of the regrain and premult.

Before going to the motion vector, we saw the Expression node and how to use it and learnt more about UV. 

The Smart Vector node calculates all the pixels which have moved and produces a video which later can be tracked in Vector Distort. The Vector Distort has different output options the default is Wasrped Src, this potion is too heavy and might slow the project. Next, the St-Map option is lighter than Wasrped Src.

Last week saw how to despill images, and this week’s class started by showing us how to protect areas where you needed to keep the green, for example, if the actor is holding a green bag or the acter eyes are green. To protect this we can use marge operations in this way.

Minus: by minus Original from the despill plate you get the luminosity lost by removing green.

Multiply: the background over those luminosity values.

Plus: it is over original to add a background in the transparencies.

We can also, use the saturate node to desaturate and this help to remove unwanted colours.

Add Mix was a new node we used in this class, Add Mix works like a marge but with Add Mix, we can control the alpha from both channels by utilising the graph.  

Additive Key is not a node but it is an image-blending technique used to recover fine detail in difficult areas such as hair, soft transparencies and motion blur, edge treatment and despill can create very good results to better integrate your plate to the background Additive Key manipulates lightness values in the fine details and adds it to the background under the foreground plate. To create this you need to take an average of the plate by using a constant and then minus it with the plate. Use the Saturation to despill then use Grade to adjust the alpha, and then Merge to the background.

Sometimes when working with greenscreen we might get lucky by getting a clean plate, which means a plate only with the background. This helps a lot when you get this because we don’t have to do IBK and just use divide and multiply to remove the greenscreen.

In the next, we saw how it affects only the ages of the hair to get more of the dilates. By using the colour Lookup node we can control the RGBA to only affects the particular area. Then mask we can mask it with a roto. Mask to the grade and adjust the transparency.

we also saw how to make take alpha from an image without using any key, but this way take an average of the greenscreen and then the difference it with the plate.

Edge Smearing Gizmo, help to restore the edge of the image. This gizmo works better than Edge Extend and is softer. Next, we saw how to make our own Gizmo and I felt this was very helpful for making our work easier.

For the next few weeks, we will be taught about greenscreen and the best way to remove it by using a nuke. This week’s class is about the bases of greenscreen.

The class started off by explaining to us about RGB and HSV, we all knew what was RGB (red, green and yellow), but HSV was something we were not sure of. The HSV which stands for Hue Saturation Value the scale provides a numerical readout of your image that corresponds to the colour names contained therein. RGB can also tell us about the HSV, its broke into.

R = HUE: Hue means colour

G = Saturation: Saturation pertains to the amount of white light mixed with a hue.

B = Luminance: Luminance is a measure to describe the perceived brightness of a colour

By using the RGB and HSL the keyer node ( AKA Luminance key) crates alpha for an image or a video. The node also has different operations like a red key, green key and blue key. The keyer has a range which is a graph where you can control the range of the area getting affected. 

Next, we used a shuffle node to isolate colours, for example, we used only one colour like red in the input and for the output connected to all the other colours but not the alpha. Use merge to minus different colours from each other. Using the same technic we remove an area, by just adding an Add mate node and keeping the value at 1 and adding an invert node. Adding a roto can help to affect only one area. Doing this helps to change the colour of an area and it’s easier to roto.

Nuke has a lot of options when coming to keys like:

 IBK Colour and IBK Giamo: IBK stands for Image Based Keyer. It operates with a subtractive or different methodology. It is one of the best keyers in NUKE for getting detail out of fine hair and severely motion-blurred edges.

Chroma Keyer: tends to work better with more evenly lit screens that are more of a saturated colour. NUKE’s chroma keyer is that it takes full advantage of any GPU device you have in your system over the other software.

Key Light: It is a really great keyer overall and does colour spill.

Primatte: This is a 3D keyer. It uses a special algorithm that puts the colours into 3D colour space and creates a 3d geometric shape to select colours from that space.

Ultimatte: keys that are good to get detail and pull shadows and transparency from the same image.

Despill is prose when you remove the green which has reflected on an object. When the object standing in front of the green scene the skin reflects the green colour. We can use IBK or the Keylight to despill. 

For homework, we had to add an image by removing the green screen from the video.