As many of you already know colour filters can be applied to a lens while shooting with B&W film in order to dramatise the final result. It’s not only for dramatisation it can also be used to create subtle pleasing tonal effects to make your artwork really stand out.
The only reason I am writing this is because I keep seeing questions regarding this popping up in online forums asking such things as; “What colours do what?” and “Should I use red filter for landscapes?” etc. So below will be some technical information on the way our eyes see colour and how you can apply that to B&W photography.
Firstly lets talk about colours. Colours are essentially rays of light (Sunlight/Artificial light) that is reflected off objects and into our eyes. As some of you already know, White light is a reflection of all the colours in the visible spectrum. Black is obviously the absense of light.
Below is a colour wheel that shows the spectrum of visible light the way our eyes see it. (think of Cyan as “Sky blue” and this will help you identify filters.)
In the colour wheel above the letters represent the colour values. C = Cyan, M = Magenta and Y = Yellow. K is not listed as it stands for “Key Colour” which is the same as saying “Black.”
These colours are adjacent to the primary colours on the colour wheel which are Red, Green and Blue. They are no longer considered a true visual representation of colour. every time an image is converted from CMYK to RGB you will notice the colour shifts 30deg but I digress.
The important thing to mention regarding B&W film and colour filters is that the filter will absorb the colour opposite it on the colour wheel. If you have a red filter then cyan will be absorbed thus not reaching the film. If Cyan doesn’t reach the film than any areas of the image with cyan will turn out black, or at least very dark. (think of this as in the sky where the blue sky part will be very dark and the clouds will remain fluffy and white.)
So what other colours can be used for B&W film I hear you ask? Well the answer is simple. Any other colours can be used. Think about a subject then look at the colour wheel and work out what will be absorbed and what will hit the film. Think about how you can make use of certain colours to create a certain look.
Here is a quick write up for using coloured filters on b&w
Red filters are used to darken the sky in landscape photography, it will create a dramatic effect that is quite conspicuous so be careful!
Orange filters lighten reds so they can be used in portraiture to reduce the appearance of skin blemishes and uneven tones.
Yellow filters are very subtle, in landscape photography they will very slightly darken the shade of the sky but can also be used to create contrast in other situations and are favoured by portrait photographers for pleasing skin tones.
Blue filters are less often used with b&w film and would have a contrast reducing and haze increasing effect.
Green filters can be used in portraiture for pleasing skin tones as well as showing tonal variance in very green scene’s such as in a forest.
That covers the general coloured filters for B&W film photography. However I must mention that some of the above filters will be quite a dark colour and require exposure compensation. The filters are assigned a filter factor depending on how dark they are and the filter factor will help you determine how to adjust your exposure based on the filter of choice.
For more information on filter factor visit the wikipedia Filter Factor Page
So next time you step out with your favourite TLR loaded with b&w think about how you can use filters to enhance your scene’s or portaits.
If you have any further questions on the above feel free to contact us