How to ensure I can print LARGE and CLEAR.

Hi yalegurney

You're going to need a certain number of pixels per inch or cm across the image width.

As Dave and D.Fosse have explained, the number of pixels required is dependent on viewing distance, this means that a billboard requires pretty much the same number of pixels as a double poage magazine spread.

(Viewing distance is, of course, most often a product of image size, you normally view a massive print from further away than an A4, say. Think of those massive Kodachromes in Grand Central Station).

Lets say print size is 24 inches on the larger dimension and the viewing distance requires 240 PPI. Then your image has to be a minimum of 240 x 24 = 5760 pixels. 

Dont miss out on sharpoening either. Many do. Sharpen at final ouput size and resolution.

 Also its not always "more pixels are better", if you send an A3 image to a designer and they place it at A5 its not going to look sharp, better to downsize then sharpen then send it. 

When downsizing I tend to make a copy and archive the full rez original, repeated resizes and resharpens often play havoc with image quality.

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer
google me "neil barstow colourmanagement" for lots of free articles on colour management
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If you print and image from single Camera RAW image  72 feet by 60 feet billboard size the image will be soft up close where the human eye can resolve down to 300ppi,  Even if you interpolate the RAW image's pixels up to 56GP and print the 72' x 60' image at 300ppi.   A poor quality large billboard size image will look fine from at a 100 yard distance. You may even see it as sharp.  When you interpolate an image up on down in sized you loose some image quality, However the printed image may look less pixelated interpolated up in size

There are no settings. It's just pixels. If the original photograph is of good quality, it will be suitable for reproduction at any size.

I assume you mean the Canon 5D Mark iv. In that case the sensor resolution is 6720 x 4480 pixels. While not the highest resolution on the market, it's plenty good enough for any practical purpose.

Contrary to popular myth, you don't need more pixels/higher ppi for large format printing. That's a misunderstanding. The exact same file will work for a magazine spread or a wall-sized billboard. The bigger it is, the farther away you will stand to see the image, so the effective optical resolution is the same.

There is a formula (that I can never remember) - but here's how I usually illustrate it:

First you would want to ensure you are capturing the highest resolution possible with the camera.  I'm not familiar with the Mark IV but have a 7D Mark II and there's a button "Q" that brings up a screen with all that data.  You can also find it by cycling through the options in Menu.

If you're then processing an image make sure you've set the DPI to very high.  Even if you have a huge file, if your DPI is only 72 then it will be a small image when it's printed.  I've done magazine work and have had that happen at times.  So check the file's DPI in Photoshop before you Save As.  Obviously check the print size too, since if you're printing at 6x4 postcard size and trying to blow it up to a billboard, that will be a problem.  

Good luck!