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Old 31st March 2012
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Graham_of_Rainham Graham_of_Rainham is offline
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Playing with Diffraction and coloured light

I finally got round to testing the idea of illuminating the subject with a blue light to reduce the effect of diffraction.

I pressed to service my ever co-operative muse for this crude set of tests

With the camera set to f/22 and manual focus, I took 3 pictures.
The one above, with the bare flash, one with a Red gel over the flash and another with a Blue gel

I then removed the colour from the RAW files, examined them and cropped an area which I think best shows the effect.

RED Light

Blue Light

The filters used are very saturated "effects" filters and beyond any colours that you would get from natural light, but serve to show how the longer wavelength of the red light is diffracted more than the short wavelength blue light.

As we all know when using filters on the lens for B&W photography, they alter the contrast and other aspects of the final image, depending on how the subject absorbs and reflects the different coloured light.

What is interesting is just how good an Olympus 14-42 kit lens is at f/22

We often repeat the mistakes we most enjoy...
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