Resolution Help Please!

[Jade16]

I sent a digital image to a client. They said when they tried to upload it to a website to print a canvas a warning popped up saying the resolution was not high enough. It is a black/white photo and I did have to do some cropping. Any suggestions on how to correct this? Is it because it is a black/white photo? Is it because of the cropping? PLEASE HELP! The resolution of the picture is of 3179 x 2119. I really want to make the client happy.

 

[tirediron]

What size do they want to print it out at? At just a hair under 200 PPI, that will allow you to print 11x16.

 

[dennybeall]

So there's your clue, take the poster size you want, in inches, and multiply times 200. That will give you the size you need to create with Photoshop or whatever software you have.
20"X30" then 4000 X 6000.

 

[KmH]

The resolution of the picture is of 3179 x 2119.

Yes, that is the image resolution.
The warning was that the print resolution was insufficient.
Image resolution AND print resolution determine print size.

What is the minimum print resolution the lab that was going to print the canvas have?
What size canvas did the client want to order?
Most labs have a minimum print resolution of around 100 pixels per inch.

Image resolution (pixels)/ print resolution (pixels per inch, ppi) = print size (in inches)
And from that simple equation we can use basic algebra to derive 2 other very useful equations that solve for image and print resolution.
Image resolution / print size = print resolution
Print size x print resolution = Image resolution

As John (tirediron) mentions, and using the appropriate equation from above:
3179 pixels / 16 inches = 198.7 ppi

31279 / 100 ppi = 31.79 inches

Note too that 3179 x 2119 pixels is a 3:2 aspect ratio. If the client is wanting a canvas that has a different aspect ratio some portion of the 3179 x 2119 pixels has to be cropped away.