DNG downsizing?

[Pacoh]

At the Photoshop virtual summit, in a presentation on noise removal there was a tongue-in-cheek suggestion that you might purchase a different camera with lower pixel density. Most new cameras do have sensors with more pixel sights than are generally needed and fewer pixels would eliminate much of the noise. But you really don't need a new camera because PS will allow you to export to a file with fewer pixels and that will have much the same effect. At the same time, fewer pixels will process faster and require less storage space. You do limit options if you need to crop the image for example; there are trade-offs. But there are some operations in PS that are available only for RAW files.

This raises the question of whether DNG files could be exported with reduced pixel counts, maybe with only a few choices such as 1/4 and 1/16? It seems like this would be fairly easy to do and could sometimes be useful.

[D Fosse]

It's not as simple as downsampling raw sensor data.  It would break the Bayer filter pattern and render it unprocessable.

The only way to do it is to first demosaic, to produce an RGB linear DNG, and then downsample.

This is why "M" and "S" raw files don't work in Denoise. It requires mosaic data.

[Pacoh]

I admit to a lack of experience with this topic, but this consideration was why I suggested limiting the reduction to 1/4 or 1/16. Or perhaps there would be other sizes that make  the conversion easy.   

[D Fosse]

There might be an indication in the current Super Resolution feature. It scales up, not down - but notably, it produces a demosaiced RGB result. This is also a regular ratio turning 1 pixel into 4.

It's also worth noting that all camera-native reduced size raw files (that I know of) produce demosaiced RGB files. There must be a reason for that. Demosaicing in itself triples file size, so the size reduction has to be quite dramatic to give any real payoff.