Re: Why 4k?

Typically, taking into account bayer pattern and optical low pass filter (you do need one on your camera, be it 3 chip and prism or single chip to avoid the grossest nasties of aliasing) you typically measure about 70% of the linear pixel dimension. However, I'm measuring nearly 80% now, which is very good. I find it funny when you read that some affordable HD cameras measure 1000 lines per picture height, when their sensors are just 1080 pixels high. Then you look at a test chart and see the aliasing in the top frequency bands and understand why.... :-)

OLPFs have a slow roll-off of high frequencies, so they cannot work like a brick wall filter that you'd design in electronics. Lack of negative light stops us designing OLPFs like that :-) That means to get good attenuation for the high frequencies, you've got to bring them in early. However, that's better than the gross aliasing you see in more affordable single and 3 chip cameras.

Of course, the above could apply to a DSLR just as much to RED.

Graeme

- www.nattress.com - Film Effects and Standards Conversion for FCP