This post is different than the previous ones. Only the technical facts, for those who have always wanted to ask but were afraid to do so or didn’t know how. So, here it is: Canon 5D Mark III and color grading on the example of the latest official promo video for Alderney.
Canon 5D Mark III is known in the motion picture industry for its high quality video recording in Full HD (1080p). The quality is achieved with the 22.3 megapixel full frame CMOS sensor, which offers a sensitivity range starting from ISO 100 up to ISO 25600, which can be extended down to ISO 50 and up to ISO 102800. Image processing is possible with the 14-bit DIGIC 5+ processor. The main advantage of Canon’s 5D is the vividness of the image that definitely stands out with its “cinematic” quality among the professional video cameras. By pro I do not mean film cameras. And there’s more – image sharpness, much better dealing with the rolling shutter effect than the competition offers and shallow depth of field. All these features make the 5D the most frequently chosen DSRL used for filming. And that would be it when it comes to Canon 5D Mark III – as this post is not supposed to be about the camera, but about color grading of the footage recorded with the 5D model.
Picture from the sensor is compressed (H.264 codec) and stored in the camera as an 8-bit signal with YCbCr 4:2:0 color space. This is the biggest shortcoming of the flagship mirror from Canon.
8-bit color depth makes the color, that is the RGB, displayable in 256 shades (0-255). It’s the so-called n-bit representation of colors, in this case 28=256. The 4:2:0 designation expresses the sampling method of Y luminance and CbCr chrominance (difference signals of blue and red). In short, the image captured by the camera is composed of pixels. Pixels are defined by means of “luminance”, which determines how bright the pixel should be, and “chrominance”, which determines the color of the pixel. If you remove the chrominance information from the image, you’ll get a black and white picture. If you delete the luminance data – the image will disappear. Thus, each pixel must contain the information about its luminance, but not all of the pixels must have the information about chrominance (the human eye is not sensitive enough to notice that and can be cheated in such a way). And so the size of the material can be significantly reduced, by saving the full information about the brightness of the pixel and partial averaged value of the color (chrominance). By the way, our eyes are most sensitive to the green-yellow color. Below the different types of sampling in the YCbCr color space are illustrated.
If you want to significantly change the colors of the recorded material during the post-production, with only 256 shades of each RGB component and incomplete information about the colors – expect many problems and a disappointing end result.
During the processing of such a signal, artefacts tend to appear when you change a specific color, ruining the whole picture. However, even if the format of the recorded image is of low quality, it definitely shouldn’t stop you from “coloring”. Just bear in mind that it will take much more time, and sometimes it might be necessary to change your concept with respect to the colors of the footage – more specifically, not to alter them too much :)
Our last project – promo video for Alderney – was made with Canon 5D, with the use of Magic Lantern firmware and CineStyle profile.
With this profile the recorded picture is “flat”, and its tonal range is between 10.5-11.5 of aperture level (registering more details with more light or in the darkness). Arri Alexa motion picture camera has a 14-level tonal range). These changes on the one hand facilitate the subsequent color grading, because it’s easier to give the image the desired style/color, but on the other hand, with 8-bit signal the range of color shades is reduced from 0-255 to 16-235 (the data in the lower and upper range – black and white – are removed). Therefore, during the recording we had to be even more careful and ensure that the setting of each scene was almost perfect.
In the last phase of post-production, i.e. color grading, we wanted to give the Alderney – So Close So Different video a more cinematic character. Although the image vividness achievable with Canon 5D is really impressive, it still looks digital. It is still incomparable to the Super 35 film. Everyone has different preferences, but for us no digital signal can match the vividness of a film stock and its natural noise. And we are huge fans of grain :)
Therefore, using the DaVinci Resolve software, we wanted to make the digital image of Canon 5D (H.264 8-bit 4:2:0) resemble that of the film stock even just a little bit. After 4 days of struggle from the early morning until late night hours, mainly with the color of the sky and dark places (where the number of artefacts multiplied even with the smallest changes), we finally achieved the desired effect. You can see it here: Alderney Channel Island. So close so different.
The video at the beginning of this post shows a comparison of the motion picture before and after coloring. Of course, the final version has been complemented with grain – unfortunately, the additional compression on Vimeo after uploading the video to the server makes it impossible to fully enjoy the magic of the grain effect!
Lastly, the even older test comparing the standard 8-bit footage from Canon 5D to 14-bit RAW format, recorded with the 5D of course, using the Magic Lantern:
The video shows the difference in the quality of the material, the amount of details stored (3x crop) and color grading – in this case, with the 8-bit display the overlapping of green is heavily visible on the hair. This green shade is caused by averaging of the chrominance at 4:2:0 sampling. Of course the intensity of the green color on the hair can be reduced, but it would require spending much more time on this single shot, and even so the end result would not be the same as with the RAW footage. In terms of the 14-bit signal, the change of red to blue is not a problem at all. While editing a standard footage made with Canon 5D, you have to bear in mind that it will be quite a tiring fun. Good luck! :)