STOP PRESS: It’s been found that this modification is also changing the exposure and dynamic range! See bottom of post.

Well, Paul Ream over at http://extrashot.co.uk/ has worked out how to make the F5 record 4K internally. It’s actually pretty straight forward. The camera can save a file called an “All File” on an SD card to memorise the way it’s set up. By mdifying this file you can trick the F5 to go into 4K or UHD frame size instead of the usual HD or 2K. First you have to modify line 15o of an existing All File (they are simple text files) where the frame rate and frame size are saved using a text editor, putting in the frame size you want. Then delete line 1 where the files MD5 checksum is stored. Save the file. Next determine the checksum of the file, then add the new checksum to line 1 and finally save the file to the SD card and read it in to the camera. By loading this modified (hacked???) all file in to the camera you can enable 4K and UHD recording to the SxS cards.

It’s certainly created a stir. Many F55 owners think they have been short changed because of this hack and of course most F5 are very happy. It will be interesting to see if any other F55 features can be unlocked on the F5 such as 4K output or 4K playback. Right now the hack is a little limited as you can’t even playback files to see if they are OK. Full details over on Extrashot in the latest podcast…. if you can grind your way through the bit on shoes and iphones without nodding off first.

UPDATE: So, now a few people have tried this, there have been a couple of reports of the dynamic range of image clipping and some other issues. I’ve had a quick look on an F5 (not mine, I’m travelling) and there is most definitely something odd going on as the pictures are darker and clip earlier in 4K XAVC compared to HD and 2K. I need to test this further to see what’s going on, but it’s not quite as perfect as perhaps hoped.

What we know: The hack tricks the camera into behaving like a PMW-F55. We know the F5 and F55 have different sensors with very different behaviour, different colour filters and different sensitivity, so the processing must be different for these two cameras.

My very quick test, shooting the same scene in 4K and in normal HD XAVC shows the 4K to be darker. Others are reporting that the 4K clips appear to over-exposure more readily than the HD.

SPECULATION: If the hack is doing more than just turning on 4K recording, if it is making the camera use the F55’s processing, then there will be a miss-match between the sensor and the processing and this might cause issues with dynamic range, gain and colour.

As soon as I get a chance (should be tomorrow) I will do some more involved testing to see exactly what is going on.