The Colour of Light
The difficulty I’ve had from the beginning was the light. Firstly, light is ‘coloured’ depending on the source. Its referred to as Colour Temperature. When I started recording videos and photographing paintings I would adjust the presets on the camera to match the light source. For example, tungsten lighting, or fluorescent. The preset settings on the camera are fine for most cases but not precise or consistent enough for what I was doing. Tungsten light varies from bulb to bulb, as does fluorescent, and this was noticeable when the same painting was photographed in different rooms using the appropriate camera preset. The photographs were slightly different. I then used a standard white card to set the White Balance on the camera (most digital cameras allow you to do this). This was a vast improvement over using the presets as the light ‘temperature’ is measured and this is used as the setting. This means that using the same white card gives consistent results under slightly different light sources. The white card may pose a problem. White cards from different manufacturers are slightly different, varying from warm cream to cool blue. They are all white, until placed side by side, then you see the difference. You can try and find a middle ground card and stick with this. If you think your results using this card aren’t right, change the card. An official ‘standard card’ can be purchased from a photographic supplier.
Video Image and Photographic Image
However, I found slight differences between the image in a video and a photographic image taken at the same time with the same settings. Its to do with the way the image was recorded, as a video or still photograph. This was very noticeable using fluorescent light. Fluorescent lights flicker on and off at a rate of about 60 times per second and this is varying from second to second. A video taken at one thirtieth of a second shutter speed, should get 2 fluorescent flashes per frame, but it can be more or less, and this will affect the exposure. Its seen as black bands moving up or down the resultant video. A still photograph, taken with a long exposure of half a second, will get approximately 30 flashes in the half second the shutter is open. But this varies from photo to photo, but the differences are small. All this flashing really confuses the automatic exposure in the camera so every setting has to be on manual.
So the solution, I thought, was to use incandescent light, like tungsten standard bulbs. These don’t flicker but the problem was heat. The lights had to be positioned in a particular way to avoid the gloss of the wet paint (more about this later). As I painted and recorded in a single session of about 2 hours, the heat from the lights was unbearable.
In the end I purchased 2 fluorescent photographic lights and although the manufacturer’s instructions said to set the White Balance on the camera manually to 4000K, by experiment I found the correct setting for the lights was 4400K. These flicker like standard fluorescent lights but at a much higher rate. So the variations are less noticeable. Now the video of a painting looks the same as the still photograph of the same painting and all paintings photographed under exactly the same conditions have the same ‘relative’ colour balance.
The position of the lights
The next issue I struggled with was the position of the lights. Oil paint, when wet, is glossy. When it finally dries the colours change so its made wet and glossy again by oiling out. Varnishing to matt, satin or gloss takes place months after the painting dries. I video and then photograph the wet painting as I’m painting, so gloss is a big issue for me.
The rule is: the light source should be at 90 degrees to the camera, simple.
If you want to video or photograph as you are painting, you and the camera cannot be in the same position. The solution was to paint flat on a tabletop. I’m on one side looking down and the camera is opposite me on the other side of the table, also looking down. The camera will be within reach to press the shutter or make adjustments.
The lights are each side at a low angle so the reflected gloss does not affect me or the camera. There will be a slight variation in lighting across the surface of the painting with the sides nearest the lights a little brighter than the middle. By adjusting the distance and height of the lights, avoiding the gloss, this can minimised but never really completely eliminated.
I see the painting right way up, of course, but the video is upside down. The simplest way of correcting this is to invert the video in a movie editor, otherwise the camera has to be mounted upside down while making the video. The video is a little bit skewed but that’s OK for a video. The photograph taken with this arrangement is also skewed and this is corrected in Photoshop but I have to be careful that Photoshop doesn’t apply a colour profile different to the one I photographed with.
Having worked through this process makes me wonder about the torturous lengths painters go through to have accurate colour matching of their subjects in paintings. The colour of natural light varies from morning to dusk, from sunshine to shade or overcast. Artificial light varies with every light source. We don’t see the difference as the ‘automatic’ adjustment in the brain masks the differences. The painting produced in ‘natural’ light and hung in a gallery under artificial light are completely different in colour and we don’t notice the difference. Furthermore, no two people see in the same way and many people are partially colour blind (especially men) and they aren’t even aware of it. So much for accurate colour matching – all colour is relative.