Green Screen Exercise
Orginal Footage
This what my footage looked like before I started to apply some effects.
Edited Footage
So here is my first attempt for the green screen exercise. Firstly I used the keylight effect to remove the green screen from the footage. I adjusted the screen gain and the screen balance variables to try and make the keying as effective as possible. There was also some issues with parts of the image that were not covered by the green screen so I ended up creating a rough mask around the subject and animating it to follow her through the shot so I could eliminate the surrounding elements. The screen matte settings for clip black and clip white were also adjusted to further sharpen up the keying.
The difference between the background image I used and the footage was very different so I tried to make some adjustments to both the subject footage and the background image to pull them together. The subject footage I added a shadow/highlight effect to try and take away some of the heavy shadows then added a small amount of blend with original image to keep it looking natural. Brightness and contrast were also added effects that proved helpful in matching up the feel of the background and the foreground. Lastly I added a warming filter to the subject as my background had a lot of warm colours and the original foreground footage looked a little too cool for my scene.
The first element of the background that did not look right was the sharpness of the image. My photo resolution was significantly higher than the foreground footage so I was forced to scale down the resolution to help fit with the foreground. I used a color balance effect on the background so I could bring down the blues a little and make the reds pop out more. I wanted to create a warmer scene rather than a cooler one as the harsh shadows suggested a strong light source which I interpreted as a harsh sun. Again the brightness and contrast were adjusted to bring the images more into line with each other.
Final Version
Here I scaled down the foreground footage and also blurred the background a little more to take away from the sharpness of it. I also added a light source on the top right hand side to give the background more of a cohesive feel with the foreground.
Rotoscoping Exercise
Here is my first attempt at rotoscoping. I used the roto brush and the refine edge tool to eliminate some elements the green screen failed to do. The subjects right arm and shoulder in particular appeared to have some heavy black outlines which I tried to focus on for rotoscoping as it was the most obvious problem.
Here are a couple of screen shots with before and after comparisons from the rotoscoping
These are some shots of the roto brush and the refine tool. The left hand side of the character was showing some heavy black lines which required the refine brush to clean up. My digital drawing tablet came in very handy for this part of the process as selecting the curved lines would have been a bit more challenging with a mouse.
Tracking Exercise
What an absolute nightmare! After Effects decided to make this as difficult as possible for me. First off I could not track my footage and was continually giving me an error message which I could not fix. I googled the problem and tried several different fixes but it just was not happening.
Then after switching to a single point track for simplicity sake I began to make some progress and then as I was manually fine tuning the key frames After Effects crashed. Started tracking again and crash. So I left it for a bit and came back to find CC was updating my After Effects so I could not run the program. The following day I went to fire up AE again and an error message. I had gone from frequent crashes to a complete inability to start the program, fantastic. After a few different attempts at fixing the problem to no avail I decided to do a complete reinstall. More time lost. So finally after countless hours of issues I was able to get some tracking in. Awesome, now I just send it over to the media encoder to render out and crash. This time my entire system was crashing. WOW! Restarted and try again….windows crash. Not only was it crashing but now it was crashing MY WHOLE SYSTEM! I came back did some more research and decided to free up some memory in case that was the issue. Eventually I was able to render out my composition but what should have taken me a couple hours took up all my study time for 2 days.
So here is my first completed tracking example.
This is a copy of my tracking path. I tracked the pendant then replaced it with an image I found from google. From there it was a matter of moving it over to Photoshop removing everything besides the pendant and putting it on a transparent background.
From here I dropped the brightness and contrast and also added some keyframes for when the pendant passes through shadow to try and give the appearance of it looking darker for those frames when it would have had less light.
So after some clarification it turns out I only needed to track the background. Since I had already figured out the process it was a simple matter of duplicating the background layer, removing all the effects then single point tracking the blue mark from the original footage. I then used the new tracking path to attach to my background along with some adjustments to the scale of the image so it stayed in the frame.
Here is an image of the path tracked from the blue marker.
And my completed Tracking exercise complete with tracked background and the altered pendant.
Colour Grading
For the final colour grading I flipped the background image as one of the tutors pointed out the light source was mismatched from the foreground to the background so this change was made to try and improve the consistency of the scene. I added a new adjustment layer and added auto colour correction, shadow/highlight effect, curves control to tweak the colour to get the desired result. I also used the vibrance effect just to bring out the colour a little more as it was starting to look a little washed out. Lastly I added a very slight hint of fast blur to just take away some those sharp transition edges.
Assignment 1 Reflections
Green Screen
The green screen process was fairly straight forward as the keylight effect really took care of the majority of the work. With a little knowledge of which variables to adjust, such as screen matte settings, the whole process was quite simple. The hardest part was getting the hair to stay in the shot without losing any detail.
The keylight settings were the most important part for optimal results I would say. As I stated earlier it was a matter of knowing what the primary variables were and a rough idea on what a good starting point was then adjusting until you reach a desirable result. Masking was important also as animating a junk mask around the subject gave the keylight less work to do and therefore less chance of getting any issues with green screen process.
Overall I was happy with the results achieved for this exercise and the skills learned in the process were a solid foundation for moving forward. I could definitely improve on retaining fine detail such as hair, I assume this is where the real skill is in green screening. In order to improve on the result I would probably have to combine it with rotoscoping to able to target specific areas as the keylight is more of a procedural approach that affects the overall outcome rather than being able to target individual areas with it’s own unique set of parameters.
Re-shoot Footage
If I was to re-shoot the footage I would have done a quite a few things different. Firstly the lighting was WAY too harsh. I would not have used such a strong light source unless it was absolutely necessary and even still I would have had a smaller secondary light source on the opposite side which would have taken away some of the harsh shadows. There is also a few frames where the subjects passes through shadow which once again I would not have done unless absolutely necessary. The green screen was fine but could have been done better if the material was tighter/flatter so shadows didn’t affect the varying shades of green making keying a little cleaner. Lastly I would have put more thought into the hair style of the subject as the small strands of hanging hair are very difficult to clean up so once again unless a definitive requirement I would have had her wearing a hat or tied her hair up more perhaps.
Rotoscoping
The rotoscoping was once again straight forward but perhaps a little more fiddly in regards to selecting and deselecting areas. Once I was satisfied with my selection the refine edge brush was needed to clean up some of the edges. This process was made easier due to my digital drawing tablet so selection of tricky areas was not a problem. The hardest part was going through frame by frame to pick out areas that could be further refined.
The trickiest part was when I refined an edge,usually the hair, and the result just gave a choppy/blurry type result with parts of the image popping in or out of the shot. In order to achieve optimal results I just needed to remain patient and go through each frame looking for areas that needed cleaning up.
I thought overall my rotoscoping was fair but could of been better. There were some areas that I could not quite decide if it looked better before or after I altered the footage. The hair in particular was very tricky.
Tracking
Track was an absolute nightmare. After updating AE the program has never run the same since. I constantly get crashes now and half the time I send things over to media encoder my whole system crashes. The actually process of tracking was quite simple really but it was the software stability that caused me more problems than anything. There were a few frames, especially when passed through shadow, where the tracker lost the mark but that was easily fixed by going frame by frame and adjusting when the tracker lost the target.
Optimal results were achieved by just reviewing the track frame by frame after it had been made to check the result was correct. I initially track the necklace and replaced it with an image I found on google. As a result I encountered a few hurdles ,such as heavy shadows, that required some problem solving however it turned out I only needed to track the background which had a clear blue marker. By the time I realized this I had already finished tracking a much more difficult target so this was relatively easy.
The tracking results turned out pretty good and I was happy with the result. By making the exercise harder on myself it actually made the whole process easier by the end. I am not sure if I could of improved on the tracking as I thought it came out pretty well.
Colour Grading
The most challenging aspect to the colour grading was probably the extensive amount o effects AE has in order to do various alterations. Had I been more experienced I could have identified what was not quite right and what effect to use to address that specific issue. Instead I kind of layered on some layers that were used in a tutorial from lynda.com that seemed to bring the balance of the foreground and background closer together. Sure it made the footage better but truthfully I did not experiment with every effect so I could not say that I used the best tools for the job as I do not know all the tools. I used some tools to improve some of the outcome but a more experienced user would have done a better job due to their knowledge of how to identify and address specific issues.
The most important effect for me I thought was the curves effect. Just the way it is easily adjustable and clear with the ability to kind of find he sweet spot in real time made this an invaluable addition, something I would definitely use again. Having a histogram to show the colour balance also gave me some confirmation I was on the right track.
I’m not sure how successful I would say the colour grading was overall. There was a definite improvement but once again I’m sure it could have been done better with more knowledge of the available tools. This could of all been improved through more trial and error but time constraints make that a little difficult which is why I say experience would be the only answer to improving this aspect.
Matt Ibbotson's DIG120 Blog 