Guess you need a primer on the differences tween raw files and rendered files. Raw files that have not been demosiaced are indeed small bcause the raw data hasn't been turned into RGB pixels yet. Once a raw file is rendered into RGB pixels, you get a much larger file, 8-bit is actually more like 3x the raw file (although that changes based on compression options when saving and whether you have backwards compatibility turned on or off). A 16-bit file will be 2x the size of an 8-bit file–again, depending on compression options. Saving a raw file in a Smart Object makes the file sizes swell considerably because it has to save the a copy of the raw file inside the rendered file plus any layers plush a composite preview.
So, what you've discovered is, it's useful to keep a raw file raw until you need a rendered file. When rendered, you'll have to expect the file sizes to be much larger...
Thanks for the reply. That makes sense insofar as one-way demosaic filters add data/interpolate the pixel data from the GRBG Bayer pattern. However, saving the 8-bit single rasterized layer image as a PNG-24 file (uncompressed) results in a 22MB file (PSD format is 95MB or 4.3x the PNG size for the same amount of image data).
I'm not privy to all the issues (slow performance, etc.) but I would have thought that after 20 years of development, PS would be using similar lossless compression for its layers upon saving.
It sounds perfectly within the boundaries of normal, expected behavior to me. Just make sure you haven't disabled compression in Photoshop Preferences.
Thanks for the verification. I double checked and don't have compression disabled.