Ever wondered why the images you so painstakingly pirated downloaded from the web for your newsletter end up printing so fuzzy when they were so sharp onscreen?
It’s a matter of resolution.
Not one of those resolutions you vow to follow each new year, but image resolution.
Think of every picture as a tightly packed bunch of dots, so tiny and in such close proximity as to appear seamless. On your monitor in takes 72 of these pixels (that’s what your monitor’s dots are called) to fill a linear inch. We will then say that your onscreen pictures display a resolution of 72 pixels per inch (ppi).
Printed materials, on the other hand, generally require more, smaller dots to fill the same area. On average, every linear inch will contain 300 dots, which translates to your images having a resolution of 300 dots per inch (dpi).
So, does this mean you will never be able to use web images (72ppi) for print (300dpi)? Not necessarily.
Say that you need to print a 7″ x 5″ picture, and you found a beautiful free pic online that you want to use. You think “72ppi, darn, there goes another good resolution,” but then discover that the image you downloaded is 2100px wide by 1500px tall.
That would be a 29″ x 21″ picture on your screen (2100/72 and 1500/72), so you would fire up PhotoShop and resize it to 7″ x 5″, print it, and start cussing because you just wasted a couple of dollars’ worth of that incredibly expensive printer ink.
That happened because by resizing you threw away a great number of perfectly good pixels, and are left with a 7″ x 5″ 72 ppi image, 504px x 360px.
What you need to do, instead, is resample, that is change the image’s resolution instead of its size.
So your resampled image will still be 2100px x 1500px, but, at a resolution of 300dpi (instead of 72), its size will be the 7″ x 5″ you needed (2100/300 x 1500/300).
Ok, can you take the image you ruined earlier and resample it to 300dpi? Well, you could, but you have only 504 pixels left to work with, so your image would be only just over 1.5″ wide (504/300).
Then why not resize it back to 2100 x 1500? Mostly because if you could create dots from nothing, you would dedicate your creative talent to producing money, instead. Think about it, if you have only $500, can you buy that $2100 sweet gadget you crave so? Whipping out your credit card is cheating and we won’t consider it.
In conclusion, when you provide images for printing, multiply the desired size by 300. That is the minimum dimension in pixels your picture needs to be.
Example: you need to print a 7″ long image. Your picture will need to be 7×300 = 2100px long.
Example 2: you have an 800 x 600 image you want to use for a brochure; what’s the maximum size you can print it? 800/300 x 600/300 = 2.67″ x 2″
Conversely, if you took a megapixel picture with your state-of-the-art digital camera and you need to use it for a webpage, resize it (throw away the extra dots) to fit within your webpage’s dimension and not require several seconds (or minutes!) to load.
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