What image size do you give customers for printing?

[Epiphany]

What size files do you give to customers for their printing purposes that are still high resolution? I use Lightroom and have my image size set at: "Resize to fit Megapixels", Megapixels set to 5.0, Resolution to 300 pixels per inch.

I have used this sizing info and printed my own pictures just fine. I find myself having to instruct other people on how to crop pictures appropriately through whatever printer they are using. Is there a better size for more uniform printing? Less fuss for customers to print their own pictures. Do you do different sizes depending on depth of field? Not sure, new to me.

Thanks!

 

[480sparky]

If someone is purchasing printing rights for a digital file, they get the original-sized. I never 'downsize', especially to 'just' 5 MP. There is no one, single MP 'size' that is 'right' for printing. Each image file is unique, and each customer's need is unique.

Not sure how your correlation with MP and DOF comes about, though.

 

[KmH]

What image size do you give customers for printing?
I give the customer an image that has the correct aspect ratio and sufficient image resolution that a high quality print the size the customer wants can be made.

Image resolution (pixels) divided by print resolution (pixels-per-inch) equals the print size (in inches).
pixels / pixels per inch = print size

In other words, a 5 MP image printed at 300 ppi will always print at the same size (in square inches). The only way to change the size is to change the print resolution.

As an example lets use 6 MP to simplify some basic math or 3000 px by 2000 px. Note too that is a 3:2 aspect ratio, the most common aspect ratio of the image sensor in DSLR cameras. Point and shoot & cell phone cameras tend to have almost square 4:3 aspect ratio image sensors.
So when we plug values into our equation:
3000 px / 300 ppi = 10 inches and 2000 px /300 ppi= 6.67 inches ..... a 10" x 6.7" print

Lets say some one wants an 8 x 10 print made from the same image.
8 x 10 is a 5:4 aspect ratio, so the 3000 by 2000 image will have to be cropped. Note that cropping means the loss of some image resolution.
At 300 ppi & 3000 px the long side of the image is already where we want it - 10 inches.
The problem is the print resolution has to be the same for both sides. So the short side lacks sufficient image resolution to get to 8 inches @ 300 ppi.

So the short side determines what we need to do to the long side to get to a 5:4 aspect ratio.
We need the short side to print so it's 8 inches long. Using the equation pixels / pixels per inch = print size we can do some simple algebra and come up with this equation: pixels / inches = ppi.
2000 px / 8 inches = 250 ppi

At 250 ppi the 3000 px long side then becomes 12 inches so we have to crop some pixels off the long side.
How many pixels is easy to determine, again using algebra to modify our equation.
inches X ppi = pixels
10 inches X 250 ppi = 2500 px. So we need to crop 500 px off the long side and get to a 5:4 aspect ratio and an 8 x 10 print that has a print resolution of 250 ppi.

If you want bigger prints you need to have more image resolution (pixels) or you have to lower the print resolution.
If you or a customer want a 20 x 16 from that 2500 x 2000 image it's now eazy-peezy to determine what the print resolution would need to be:
2500 / 20 inches = 125 ppi.

The top print labs generally have a minimum print resolution they will print from that they feel is sufficient to maintain their reputation for print quality.
That limit is usually right about 100 ppi.