Oxford School of Photography

insights into photography

What is 4K resolution and why does it matter?

I am sometimes asked by people who should probably know better than ask me about the future, “What is the next big thing in cameras?” Well there have been a number of false dawns, a couple of years ago everyone was talking about light field cameras, you take a picture and then on the computer decide what bit you want in focus, and if you don’t like it you can change it, see this post. Well so far it doesn’t seem to have taken off. People tell me cameras in phones are the next big thing, seems doubtful. Anyway for a while there have been grumblings about 4K video with the ability to grab a still of over 8mp, that means a file size of 25mb so big enough to print at full resolution without resampling up to A4. Most people don’t get close to printing up to A4 (12in x 8″ for our American friends) so that sounds OK then. The idea is that in the future we will just video everything and then grab a still from the vid. Well it might manage to capture the ‘decisive moment’ but I’m sure Henri Cartier Bresson would not have been impressed.

This article on Digital Camera World goes some of the way to explaining 4K.

Screen resolution AW 3 with annotations

This is the conclusion to the article But it’s the opportunity to capture stills from 4K footage that we’re really interested in. Creating digital images in this way is nothing new, but each frame of 4K video is 3,840×2,160 pixels – generating an 8.3MP image. By comparison, stills extracted from Full HD clips deliver images closer to 2MP.

Of greater significance is that these 8.3MP pictures are captured at up to 30 frames per second. Being able to choose a single, 8-megapixel frame from an entire sequence gives you the flexibility to isolate the ‘decisive moment’ at your leisure.

Sounds ideal, doesn’t it? But the optimum shutter speeds for recording smooth video are generally much slower than when taking photos. This can result in moving objects being blurred in the extracted frame.

The other downside is that the image will be saved in the 16:9 aspect ratio. Cropping to a more photo-friendly 3:2 or 4:3 means losing some of the picture area and reducing the possible print size.

Keen to get around these problems, Panasonic has introduced a 4K Photo mode in its new cameras, with optimised settings for still image capture.

Meanwhile, professional broadcast video cameras are now starting to offer 8K – offering four times the resolution of 4k – and 33.2 megapixel stills from each frame!

Where will it all end?

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