What the Heck Does 300 DPI Really Mean?
We regularly work with printers, or work with people who work with printers, and there’s an incredible amount of confusion about pixels, dots per inch and what the print shop really wants. In trying to explain it all to somebody, I stumbled upon two decent articles that can do the explaining for me.
The first is called The Myth of DPI, and covers the basics and the common mistake:
The client already has a beautiful digital photo with pixel dimensions of 2048 x 1536. The client notices that the photo editing software is showing that the photo is set to 72 dpi. So, following orders, the client types in 300 to reset the dpi to 300. In doing so the image is resampled and is enlarged over 4 times to pixel dimensions of 8533 x 6400. The client sends this enlarged 300 dpi photo. The print shop/graphics designer/magazine reject it (too grainy, too colour blotched). The client is crushed.
And here’s the second, on what the print shop really wants:
What they are really asking for is a photo that will print at a certain paper dimension in inches at 300 pixels per inch (PPI). If you remember from the Myth of DPI, the term DPI is a holdover from when this setting in a digital photo would set the paper output quality (resolution) of a printed image (number of printer dots per inch). This is no longer the case, but people still confuse DPI with PPI.
Go forth and print your materials with confidence, knowing they won’t come back all jaggy and blotchy.
UPDATE: Riny writes with her own article about the confusing world of DPI. Read it in both English and Dutch.
July 31st, 2006 at 11:15 am
Will use this for future reference :)
Working at a publishing house, means we have to make our authors/editors understand - this is our (badly translated) explanation:
When handing in digital images, remember:
- photo’s at a minimum of 300dpi
- linedrawings at a minimum of 600dpi
This is the minimum for the actual size of the image when it is printed in the book/journal.
Example 1: Printing a photo at the maximum width of the type area (12 cm), the photo needs to be at least 12 x 120 (120 dots per centimeter = 300 dots per inch) = 1320 pixels wide.
Example 2: Printing a line drawing which is 1200 pixels wide means the actual image can only be printed at 5 cm wide (600 dots per inch = 240 dots per centimeter –> 1200 / 240 = 5cm)
August 1st, 2006 at 1:48 am
That was one of the most difficult things as a student 10 years ago to grasp. Even when I returned to college 8 years later only to find at another institution in another province were design instructors continuing to argue vehemently amongst themselves which translated to many students graduating still not understanding the dpi/ppi difference.
Nice expanation.
August 2nd, 2006 at 9:10 am
And you didn’t even approach the topic of LPI. I used to work with a newspaper and ‘lpi’ was the term to use. The math is far easier if you just ignore the lingo.
May 18th, 2007 at 8:10 am
thanks, this is really helpful
September 6th, 2007 at 5:47 pm
[…] send in a photo, “300dpi” or better… Thus leading you on a hunt to a) figure out what 300 dpi is, whether or not your photos possess this elusive quality (probably not; right-click and select […]
November 5th, 2007 at 12:11 pm
So when the yearbook staff guy says, “We require a wallet-sized portrait-orientated photograph, 300dpi (minimum)” does he want a printed wallet-sized photograph, or a digital file that will print out to a decent-resolution wallet-sized photograph?
January 18th, 2008 at 9:53 am
[…] layout (if that’s your thing). It may take a high megapixel count to ensure you get that 300dpi, but wouldn’t it be worth […]
May 23rd, 2008 at 6:56 am
Darren, I’m working back from digital photos that have been sent (i.e. fait accompli). It’s been easy to work backward with your formula. I open the image sent in Preview, crop it and copy it, open a new window from the clipboard and read the horizontal size and compare that with a one-inch width I’m shooting for. Saved a lot of time and discussion even with the small files (well, 10 kb, ma’am, just ain’t gonna fly!). It makes me wonder, though, how would you suggest measuring going in the other direction? Will you have to physically print it out and measure? Enlarging your carbon footprint, unnecessarily. Do you view it at its “actual size” and then measure it on your screen? What’s your take on this? Thanks for your minimalist approach!