You might want to take a look at Adobe's Print Publishing Guide. A good reference book that explains ( or used to ) levels of gray, printer resolution(s), and image file resolution. What resolution and color mode ( RGB vs. CMYK ) depends on the actual output device. I used to work with an HPDesignjet5500 large format inkjet printer. Deep inside the technical literature for this particular printer is the stochastic screening frequency ( 72 lpi [ lines per inch ] ). Given that number, image resolution should be 144ppi at final size ( 72 lpi x 2 ). The symantics of all of the techical information quickly overwhelms the average user. Many people in the industry just say "give us image resolution at 300ppi" which is not correct. The challenge for you is getting image sizes up to large format without losing image resolution. Every time you enlarge an image 200% you cut the resolution in half. "What resolution should I use?" Again, it depends on the RIP and/or output device ( printer ). You could get away with a resolution as low as 72 ppi using some inkjet printers ( if you have to ) or split the difference and use 108 ppi or use max of 144 ppi ( again, depending on the printer itself ). "do I need to tweak the color profiles or will the defaults suffice?" That depends on the printer, type of media used , and the RIP. I recommend you consult with the person actually printing your large format job, ask them if they need your file CMYK or can RGB be used and, if so, what profile for either one? Most standard profiles ( the ones that are listed in Photoshop's Color Settings ) are suitable, but again, ask the print vendor. When the print vendor RIPs your job, they will use their own internal printer profile to output your job. So, based on their output profile, they will recommend a PS profile that is suitable. Most Postscript printers and RIPs will accept PSD and / or tiff file formats.
... View more