4K, 16:9, REDCODE 36 vs 4K, 2:1, REDCODE 42

[King Cheung]

Dear All,

My final output of my project will be likely to be 16:9. For sure, I will set my frame guideline as 16:9 to make sure my correct framing.

But I am considering how to choose my project setting. I know choosing 4K 16:9 will utilize the maximum area of the sensor, but I can use only REDCODE 36 as I am using CF card. Then should I choose 4K 2:1 though it will use smaller area of the sensor, but it can let me choose REDCODE 42?

In other words, my question is the quality comparison between 4K, 16:9, REDCODE 36 and 4K, 2:1, REDCODE 42.

Thanks a lot.

 

[Andrew Wilding]

Now take this with a grain of salt, (since its widely known that I never completed highschool,) but my completely unsientific opinion is that you would be muuuuch better off shooting at 16:9 RC36 then using less pixels as a higher RC setting. The compression that these geniuses have worked out is pretty staggering. The difference between even 42 and 28 is pretty infinitesimal. Go with resolution on this one. Cropping 16:9 out of 2:1 would throw away too many delicious pixels, I should think.

 

[Michael Romano]

I would have to agree with Andrew. I've compared RC28 & RC36 closely and I was hard pressed to visually detect differences. I would like to hear if anyone (Graeme?) has a word on how these codec differ. Is it just like a bit rate deal or are there more complex things going on under the hood?

 

[Graeme Nattress]

Think in terms of bits per pixel. There's actually very little difference between 2:1 and 16:9 in terms of bits per pixel. If you think about it - you're card limited, so you can either have more resolution at less bits per pixel or more bits per pixel and less resolution.

Graeme

 

[Michael Romano]

So it can be thought of as a difference in Mbps? Say you were to use 16x9, with both different codecs. The RC36 or RC42 would have a higher Mbps than the 28? Does that effect debayer technique? Do lower bits per pixel create less than 12bit final output (banding?) or is this somehow recovered in the codec scheme? Am I understanding this at all?

 

[Graeme Nattress]

They're not different codecs, they're different bit rates of the very same codec. No, they don't effect demosaic. The wavelet based REDCODE doesn't band anyway, and it's always 12bit. Difference is the lower rates can, on very high detail scenes, be ever-so-slightly softer, if noticeable at all.

Graeme

 

[Michael Romano]

I see... Thank you, I've been wondering about that for some time

 

[Jeff Kilgroe]

In addition to what Graeme said, there is one other factor to consider. If you are indeed finishing to 16:9, then you should probably shoot 4K 16:9. The difference between RC36 and RC42 is very minimal, pretty much unnoticeable under most circumstances. However, if you shoot 4K 2:1, you have to crop your frame to get 16:9 and will then be working with 3640x2048. If you shoot 4K 16:9, you can down-sample from the full 4096x2304.

 

[Andrew Wilding]

In addition to what Graeme said, there is one other factor to consider. If you are indeed finishing to 16:9, then you should probably shoot 4K 16:9. The difference between RC36 and RC42 is very minimal, pretty much unnoticeable under most circumstances. However, if you shoot 4K 2:1, you have to crop your frame to get 16:9 and will then be working with 3640x2048. If you shoot 4K 16:9, you can down-sample from the full 4096x2304.

This is more or less what I was trying to say in my first reply - only now written by someone with higher cognitive function!

 

[King Cheung]

thank you all. I understand more now.

 

[Neil Harrison]

I may be wrong here, but if you are finishing to HD 1080 would it not be best to shoot 4k HD at Redcode 42, which would give you the higher bit rate on the codec and allow better resize to 1080 (due to it being exactly 4 x the picture size) ?

Neil.

 

[Daniel Browning]

4kHD seems ideal to me too, Neil; however, I don't think it allows a "better" resize per se -- just faster. If you have the computer power to do a full-res demosaic (e.g. Red Rocket), then the resized 1080p will have equal quality (within 5%) whether it came from 4K or 4KHD. The advantage of the 4KHD comes in when you don't have the resources for a full demosaic: it allows the use of half-high to get good quality (though not best) very quickly.