Debayer Export w/o Scaling

[Mike Nagel]

Hi,

currently testing out some R1 MX footage in RCX.

IIRC - and please correct where wrong - it was mentioned in the past that Red footage after debayering is roughly 70% of the resolution and then later on it was stated it was around 80%...

So - using 80% - 5K Epic footage would result in 4K after debayer and R1 MX 4480 footage would roughly debayer to 3584...

Now, is there a way to export from RCX w/o any scaling involved ? If so, how ?

It seems to me that there are only fixed output resolution presets available, and specifically for the R1 MX they all include scaling (up or down scaling)...

There is an option to enter a custom output resolution, but in order for me to specify a resolution that does not involve scaling I'd need to know the exact loss factor when debayering (70% | 80% | etc)...

Any suggestions ?

Thanks !

- M

 

[Graeme Nattress]

Mike, you're confusing measured resolution with pixel resolution, and that's probably my fault through not explaining this well enough in the past.

Image files have a pixel resolution which is the number of pixels you have in the image. However, we can imagine that say you shot a resolution chart that was really out of focus and then, at that point although you have the very same pixel resolution in your image as you normally have, the measured resolution off the chart would be very low indeed because it's out of focus.

Now let's focus that chart and measure exactly how much detail we can see. Say we measure a number and look at that as a percentage of the image pixel resolution. Say that number is 80%. Now you have a 4k pixel resolution image with 3.3k of measured resolution. It's still a 4k image because that's the pixel resolution, but in terms of absolute level of detail it can hold, taking into account the imaging and recording system including lens, you get a bit less than 4k, and that's just the way it should work - but why?

Say the system actually showed 6k of measured resolution in that 4k file (and no, that's not bonkers - think about it, you've got a rez chart and it's showing detail not blurriness out to grey at the 6k mark) that's a really bad thing because although the chart is showing detail, it's too much detail to be contained in pixel dimensions of the file, and that means aliasing and moire and they will look bad. A link-skipping vDSLR will do this - vertically the resolution on the chart might measure 4k or so, but because it only has 1080 pixels vertically it means that any detail in the scene above 1080 will fold back, alias and moire into the image in a very destructive way that just looks plain ugly and that there's no fix for in post either.

So ideally you want no more measured resolution than you have pixel resolution as to ensure low aliasing and more, but no lower than necessary or you'll get a blurry image. At the SD and HD level this was un-acheivable because without allowing through some aliasing the image was always too soft. At the 4k and higher level we can set the system up properly so as to achieve very low aliasing and very high measured resolution.

So when you demosaic there is no scaling going on - you get a 1:1 pixel resolution off the sensor. Hope that helps explain things and why it's done this way.

Graeme

 

[Bob Gundu]

Great explanation Graeme.

 

[Mike Nagel]

Graeme,

absolutely makes sense.

Thank you very much for taking the time to explain this in detail !

So what's a rough number of measured resolution on the MX sensor ? Is it around 80% of the pixel resolution ?

Thanks !!!

- M

 

[Graeme Nattress]

Roughly around 80% yes - and this is obviously lens dependent.

Graeme

 

[Mike Nagel]

thanks, Graeme !