More 4K

digitalfilms by Oliver Peters

I?ve talked about 4K before (here, here and here), but I?ve recently done some more 4K jobs that have me thinking again. 4K means different things to different people and in terms of dimensions, there?s the issue of cinema 4K (4096 pixels wide) versus the UltraHD/QuadHD/4K 16:9 (whatever you want to call it) version of 4K (3840 pixels wide). That really doesn?t make a lot of difference, because these are close enough to be the same. There?s so much hype around it, though, that you really have to wonder if it?s ?the Emperor?s new clothes?. (Click on any of these images for expanded views.)

First of all, 4K used as a marketing term is not a resolution, it?s a frame dimension. As such, 4K is not four times the resolution of HD. That?s a measurement of area and not resolution. True resolution is usually measured in the vertical direction based on the ability to resolve fine detail (regardless of the number of pixels) and, therefore, 4K is only twice the resolution of HD at best. 4K is also not sharpness, which is a human perception affected by many things, such as lens quality, contrast, motion and grading. It?s worth watching Mark Schubin?s excellent webinar on the topic to get a clearer understanding of this. There?s also a very good discussion among top DoPs here about 4K, lighting, high dynamic range and more.

df_4kcompare_1A lot of arguments have been made that 4K cameras using a color-pattern filter method (Bayer-style), single CMOS sensor don?t even deliver the resolution they claim. The reason is that in many designs 50% of the pixels are green versus 25% each for red and blue. Green is used for luminance, which determines detail, so you do not have a 1:1 pixel relationship between green and the stated frame resolution of the sensor. That?s in part why RED developed 5K and 6K sensors and it?s why Sony uses an 8K sensor (F65) to deliver a 4K image. read more...