Perhaps I haven't understood the concept of the "Scaling Workflow" and hence my confusion ...
I checked out most of the Q&A for designing large format images on Photoshop (like for huge billboards), and the most popular suggestions were to "scale" the image down and design at high resolution.
For instance, if a billboard is to be 20' wide, the vendor may ask you to send a file 20 inches wide. If the billboard will be printed at 40ppi, then your 20" wide file would need to be set to 480ppi to allow for the scaling (12X40).
30 dpi for final output is more than enough for a billboard of that size. It's not unusual for final output to be 12-15 dpi in this context. The usual professional billboard workflow in Photoshop is to build the image at a small scale with high ppi (e.g., 4x6cm @ 300 ppi),
How does this help?
For example, let's assume a billboard's print spec is 35 meters (W) x 15 meters (H) at a resolution of 50 DPI / PPI in CMYK. And the billboard designing will be done with a raster image using Photoshop.
So how does it help if you design it at 350 cm x 150 cm @ 500 ppi (scaled to 1/10, for example) or at its actual size of 3500 cm x 1500 cm @ 50 ppi?
A 350 cm x 150 cm @ 500 PPI will have ~ 68,898 x 29,530 pixels (350 cm = 137.795 inch x 500 PPI = 68897.5 and 150 cm = 59.06 inch x 500 PPI = 29,530).
A 3500 cm x 1500 cm @ 50 PPI will also have 68,898 x 29,528 pixels (3500 cm ~ 1377.953 inch x 50 PPI = 68897.65 and 1500 cm ~ 590.56 inch x 50 PPI = 29,528).
In both cases, the file size in Photoshop is going to be approximately the same (around 4+ GB!), since the amount of pixels in both the Photoshop file will be the same! When the document size is the same for both cases, how can Photoshop use less resource for the "scaled" down size? How does it become easier to design using a "scaled" down version?
To be clear, I understand the theory of why a lower resolution works with large images for bill boards.
My question pertains to the "scaling" designing workflow that was suggested for editing large raster images (mainly in photoshop). I fail to see what benefit this approach offers, and hence my query ...