How to make a drawing 9x6 feet in Photoshop

[Kató Menges]

Hi everyone! 
I need to draw a black-and-white image in Photoshop, which then will be printed in 9x6 feet resolution and then glued to a wall in a room. I've never made something this large digitally, so I have some questions:
- What file parameters should there be? Do I have to create a file with a 1:1 ratio(madness!)?
- What DPI to choose?
- Should I start with RGB or CMYK?
- Save in .tiff?

[Derek Cross · Accepted solution]

Work in RGB or greyscale color mode, as the image is to be viewed from a distance, it can have a low resolution, say 75PPI (not DPI, which is a printer resolution). Supply a JPG or PDF/X-4  but check with the company who's printing the poster first.

[Kató Menges]

Thank you for your reply, Derek!
Would around 2100x3200 px be enough or should I create a larger file?

[Derek Cross]

108inches x75 PPI = 8100px

72 inch x75PPi = 5400px

(Check my arithmetic!)

[Kató Menges]

You've been very helpful. Thanks a lot! 

[JJMack]

9'x6' is a 3:2 aspect ratio.  Do not make a 9'x6' with a 300dpi print resolution  a 100 DPI print resolution will do and the file will be 9 time smaller then the 300DPI 9'x6' image 77,760,000 MP vs 699,840,000 MP

[Kató Menges]

Thank you!

[D Fosse]

If you're a photographer, you'll have a more immediate understanding of pixels and how many you need (not as many as a lot of people think).

My Sony a7rIII delivers 7952 x 5304 pixels. Here's the amount of detail you get with that - the second is a straight crop from the first:

Pixel sizes in this neighborhood will basically work for anything, whether magazine spread or roadside billboard.