The 4500 x 3000 image resolution file has no print size (print resolution - 300 ppi) until a print resolution is assigned.
Also, as print size increases so does viewing distance. As viewing distance increases the need for print resolution decreases.
What, in feet or inches, to you is a "very large print"?
4500 x 3000 @ 300 ppi (yep. It's ppi - not dpi) will be a 15 x 10 inch print. 4500 px / 300 ppi = 15 inches.
4500 x 3000 @ 100 ppi will be a print that is 45" by 30" and the print will be viewed from further away than a 15" x 10" print from the same 4500 x 3000 px image.
If you want to keep the same print resolution but make a much larger print the image resolution will have to be increased.
Increasing image resolution means virtual pixels have to be created by whatever software is used to up-res the image resolution.
How successful any software application can be at doing that is to a large degree dependent on image content.
Lets assume you want to make 4.5 foot (54") by 3 foot (36") print
With more simple math (a little of it basic algebra) we can calculate that
@300 ppi we need 54" x 300 ppi = 16200 px and 36" x 300 ppi =
10800 px.
That's a lot of pixels that have to be conjured up by any software that can up-res digital image files.
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