Colour grading video - file types

[Tom Pinchenzo]

I'm a bit of a beginner when it comes to video (i'm not even sure how to phrase the question) - I was wondering whether there were varying levels of file compression when recording video and what the minimum requirement would if you wanted to colour grade. I understand there is N-log with Nikon, which is the equivalent of RAW. But can you record 'non N-log' with a more bits rolleyes that would give you the latitude to colour grade. I'm looking at the Z6 and apparently to record N-log you need an external something-or-other.... I looked at a review of the Z6 for video and got confused

 

[ah5168]

There are 3 main things to contend with when looking at video quality, there is the codec which takes your raw video and squeezes it down to something more manageable but throws away a lot of information in the process. This is the same as raw and jpg in photography and you probably don't have a choice of codec when recording internally on a Z6.

You then have the bit rate which in the case of the Z6 is the data rate of the compressed footage, I think the Z6 can produce up to 144 Mbps in 4k.

Finally you have the bit depth which is the amount of colour information in each pixel, the Z6 can shoot 8 bit internally but 10 bit if you shoot to an external recorder. An external recorder will also allow you to shoot 12 bit raw and/or have a choice of codec and bit rate offering much less compression.

In reality if you shoot 8 bit internal files you wont have a lot of scope for colour grading and will need to get close to the finished product in camera, if you want to really push the files around you need 10 or 12 bit files and would need to use an external recorder.

I have been looking at using a Z6 and external recorder as a B camera but don't think the external recording option is full sorted yet. It can be made to work but it's doesn't appear very reliable at the moment. I am currently holding off waiting to see how it develops.

 

[Tom Pinchenzo]

There are 3 main things to contend with when looking at video quality, there is the codec which takes your raw video and squeezes it down to something more manageable but throws away a lot of information in the process. This is the same as raw and jpg in photography and you probably don't have a choice of codec when recording internally on a Z6.

You then have the bit rate which in the case of the Z6 is the data rate of the compressed footage, I think the Z6 can produce up to 144 Mbps in 4k.

Finally you have the bit depth which is the amount of colour information in each pixel, the Z6 can shoot 8 bit internally but 10 bit if you shoot to an external recorder. An external recorder will also allow you to shoot 12 bit raw and/or have a choice of codec and bit rate offering much less compression.

In reality if you shoot 8 bit internal files you wont have a lot of scope for colour grading and will need to get close to the finished product in camera, if you want to really push the files around you need 10 or 12 bit files and would need to use an external recorder.

I have been looking at using a Z6 and external recorder as a B camera but don't think the external recording option is full sorted yet. It can be made to work but it's doesn't appear very reliable at the moment. I am currently holding off waiting to see how it develops.

Thanks - that really help. I understand bit depth and from your description I think I understand what a codec is - but where does but rate come in? How will a better (or worse) bit rate affect your file?

 

[Tom Pinchenzo]

Also, is 10 bit different to N-log?? Is 10 bit just like a tiff and N-log is raw? And do you have to output to a dedicated external recorder or can you HDMI to a laptop?

 

[ah5168]

N-Log is a very flat colour profile like the Flat profile and 10bit is the amount of colour information, they both relate to colour information and not the level of compression. The way N-Log is configured it needs to use the 10 bit colour depth to produce all the information. If you could record 10 bit internally you could record N-Log internally. In theory I guess you could record to a laptop but I would have thought your laptop only has HDMI in. You would need some extra hardware to capture the data and process it on your laptop.

 

[Tom Pinchenzo]

N-Log is a very flat colour profile like the Flat profile and 10bit is the amount of colour information, they both relate to colour information and not the level of compression. The way N-Log is configured it needs to use the 10 bit colour depth to produce all the information. If you could record 10 bit internally you could record N-Log internally. In theory I guess you could record to a laptop but I would have thought your laptop only has HDMI in. You would need some extra hardware to capture the data and process it on your laptop.

That makes sense - final question (I promise!) what is the impact of bit rate?? What does it effect? And what’s the benefit of a higher bit rate??

 

[ah5168]

The main difference is the quality and level of detail. Lots of consumer cameras tend to produce 4K footage that's around 100 Mbps and the same cameras will produce 1080p at 25 Mbps.

Obviously lower bit rates take up less space and lower bit rates created by high compression can be slower to edit as your computer will have to work harder to uncompress each frame.