July 31st, 2006

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PR and Marketing
13 Comments »

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.

Comments: 13 Responses so far

Leonieke
July 31st, 2006
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)

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Jessica
August 1st, 2006
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.

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Olaf Gradin
August 2nd, 2006
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.

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Mark Hodson
May 18th, 2007
8:10 am

thanks, this is really helpful

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We need a 300dpi photo… « The View From Here
September 6th, 2007
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 [...]

Susan
November 5th, 2007
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?

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Light up the floor for that slick product shot | Do it Yourself
January 18th, 2008
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 [...]

Mike
May 23rd, 2008
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!

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PHP tutorials
January 5th, 2009
1:41 pm

Never clear to me

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Jake
February 8th, 2009
10:26 am

so i still don’t understand is dpi and ppi the same thing. Because I was just on this printing site that required a 300dpi and I had the image set at a 300 ppi and it still did not work

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how?
April 19th, 2009
6:37 pm

well i dont care too much about ppi or dpi, i just still confuse on how to see the length of an image without software.. i mean the physical length(cm, inch, etc) not the pixel..

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Keith
January 4th, 2010
9:42 am

Thanks, very helpful!

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Newbee
January 22nd, 2010
4:41 pm

I have no photography background, but I have been told i take some pretty good photos and I am going to take a huge risk and send in some of my photos to a contest but they are asking that my photos be between 150 and 300 RGB.DPI. I read what has been written above and am still confused. I am guessing these numbers are refering to once I download the photos into my scanner…and from there I must check the pixels to make sure they fall into that numeric category? Oy, I am so out of my league right now! I am crazy for even trying this!!

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