There is not one week in a year when clients would not send me photos for print projects which are far too small for printing.
This to me shows the influence of the web over the last 10 years. We are used to seeing images online, Google's image search is our best friend.
Quite often I can tell that these photos have been pinched from the Net, sometimes to illustrate the clients' preferences, but most of the time they are send for printing.
In 99 of 100 cases I have to send them back. It's not just because most images on the Net are under copyright, it's also that the resolution of web images just doesn't work for printing.
The majority of web images has a resolution of 72 or 96 pixels per inch. The more pixels per inch, the sharper the image.
Webimages are mainly jpgs. Jpgs are compressed images, because webimages can't be too large in kB, otherwise it would take ages for a website to open. But compressing causes quality loss in colour and detail.
With each image there is only a certain amount of pixels available. Enlarging that image means that the existing pixels just get enlarged, not multiplied. That doesn't work, the whole photo just gets blurrier.
Think of stretching a chewing gum and you know what I mean.
Images in print have to have a higher resolution for sharp and crisp results. Paper is different to a screen, where the backlight alone makes photos looking crisp and nice. For paper an image has to be perfect.
The standard resolution for print images is 250-300 pixels per inch, although some printers do now work with 200.
Let's do the maths:
A photo that should take up, let's say, 10cm x 10cm in a brochure:
10cm x 10cm @ 300 pixels per inch = 1180 pixels in width and 1180 pixels in height = 1,392,400 pixels. This is roughly 4 MB in size.
A web image, the same size of 10cm x 10cm, but in 72 pixels per inch: 283 pixels in width and 283 pixels in height = 80,089 pixels. And ca 235 kB in size.
This is 17 times less than the print file.
Most images on the Net are smaller than 10 cm x 10 cm. Even if that image might look sharp in 72 pixels per inch, as soon as it gets converted to 300 pixels per inch it shrinks in size.
Sample: The webimage is 5cm x 4cm large, in 72 pixels per inch, which are 16,046 pixels.
For printing this image now has to be converted to 300 pixels per inch. As we only have a set number of pixels available this would mean that there are just enough there to cover a space of 12mm x 9mm.
This is how the image, that looked ok on screen, ended up in print:
To make a long story short - for amazing print results, photos have to be properly sized.