Photography Printing Guide

v1.0, 2005.12.27

dpi is NOT THE SAME as ppi !!

Even though "dots per inch" (dpi) and "pixels per inch" (ppi) are used interchangeably by many, they are not the same thing. Traditional printing methods use patterns of dots to render photographic images on a printed page. While pixels on a monitor are square and in contact with the adjacent pixels, printed dots have space between them to make white, or no space between them to make black. Color photographs are printed using four inks, Cyan, Magenta, Yellow, and Black (CMYK), and four separate dot patterns, one for each ink. Dots per inch (dpi) refers to printed dots and the space between them, while pixels per inch (ppi) refers to the square pixels in a digital image. Keep in mind that many companies will ask for images at 300dpi when they really mean 300ppi.

Why do I need 300ppi for a "photo quality" image?

First, some background information is necessary. A digital image is what it is. It is however many pixels wide by however many pixels tall. If you divide each dimension by 300, you will have the size of the image at 300ppi. Now think about 300 pixels in an inch of space. Each pixel could be black, white, or any other color, but they are all next to each other with no spaces between them. When a digital image is prepared for reproduction on a printing press, pixels are converted to dots. Dots have spaces between them. 300 pixels become 150 dots and spaces, so 300ppi becomes roughly 150dpi. 150dpi is the accepted standard for printing photographic quality images.

Printers usually refer to the number of rows or lines per inch (LPI). 150 lines per inch is simply 150 rows of 150 dots per inch. 150 LPI and 133 LPI have long been the established standards for the best quality reproduction of photographs in books and magazines. Newspapers traditionally use 85 LPI for photographs and detail is lost because the dots are plainly visible.

Viewing distance changes everything!

Everything is relative to viewing distance. 150dpi (or 300ppi) is accepted as photo quality because the average person cannot see the "dots" at a few inches away. A real photograph made from film in a darkroom has no dots or pixels and therefore is the standard by which "photo quality" is judged. When you move the viewer further away from the printed material, lower dpi is acceptable. A huge billboard might be printed at only 40dpi but no one notices because everyone is 50 yards away from it.

I always see "72dpi". Where is that used?

72dpi should really be 72ppi because most likely, it has nothing to do with printing. Most of the time, 72dpi refers to output on a computer monitor. A 72 pixel by 72 pixel image should take up about one inch of space on the screen. This of course depends on the size of the monitor and what resolution it is set to. When creating images for web sites, we've found it's best to determine what screen resolutions will be used most often by that site's visitors, instead of thinking about inches at all.


Megapixels vs. Maximum Print Size Chart

Megapixels Pixel Resolution* Print Size @ 300ppi Print size @ 200ppi Print size @ 150ppi**

3

 2048 x 1536 6.82" x 5.12" 10.24" x 7.68" 13.65" x 10.24"

4

 2464 x 1632 8.21" x 5.44" 12.32" x 8.16" 16.42" x 10.88"

6

 3008 x 2000 10.02" x 6.67" 15.04" x 10.00" 20.05" x 13.34"

8

 3264 x 2448 10.88" x 8.16" 16.32" x 12.24" 21.76" x 16.32"

10

 3872 x 2592 12.91" x 8.64" 19.36" x 12.96" 25.81" x 17.28"

12

 4290 x 2800 14.30" x 9.34" 21.45" x 14.00" 28.60" x 18.67"

16

 4920 x 3264 16.40" x 10.88" 24.60" x 16.32" 32.80" x 21.76"
35mm film, scanned 5380 x 3620 17.93" x 12.06" 26.90" x 18.10" 35.87" x 24.13"


*Typical Resolution. Actual pixel dimensions vary from camera to camera.

**At 150ppi, printed images will have visible pixels and details will look "fuzzy".

For a chart of megapixels vs. maximum print size at 300ppi,
see our Megapixels Chart.


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[19 Comments]


  

Great Job

08 Jun 2007 4:36pm

"I've read your charts and the information given in these topics are just wonderful. It's added a big amount of information in my photography data back in my mind. I didn't have so much idea about the pixel or ppi and dpi stuff but it's really gonna help me a lot in future. Now I can really think of buying a proper SLR or other digital cam which would suit my requirements. Please add some detailed know how of SLR's, like what they are or how they different from other cams. Thanks Vikas Verma"
 


  

Article on DPI andPPI

10 Nov 2007 7:43am

"I worked as a lithographer for over ten years. I have a very clear understanding of what DPI is. You did a great job in describing the difference between DPI and PPI. Do you think you could go a step futher and explain that overlapping the CYMK dots results in seeing all the colors of an image (picture)."
 


  

typesetting measures

17 Feb 2008 9:40am

"Thank you for trying to dispel some of the many myths when it comes to photography and printing. A couple of nits about the article. All color monitors that I am aware of (CRTs and LCDs) actually have black spaces between the imaging areas. They are small, but they are there. Secondly, I believe that the 72 DPI has a lot to do with printing. A typesetting Point is about 1/72 inch. There are 12 Points to a Pica."
 


  

joe

08 Mar 2008 9:33am

"people still use the term dpi over ppi so much. even the most respected web sites."
 


  

Canon 350

24 Apr 2008 4:25am

"extremely useful. Googled a lot of words till I came up with this page. Pretty much what I was looking for- dpi, ppi, megapixels and size of prints."
 


  

Way cool

21 May 2008 11:30am

"I have read many explanations from various photo forums and other technical (professional) sites on this topic, DPI vs PPI and printing size. I am no longer unsure of what those terms mean and why they are used (and misused). Thanks, Peter Ellis"
 


  

Traci Refior

01 Jun 2008 7:09pm

"Thank you so much for reminding me of these very crucial points!"
 


  

ian

02 Jun 2008 8:57am

"great information, thanks for taking the time to table the usefull information. :)"
 


  

Lorenzo

05 Jun 2008 8:37am

"Excellent, this is exactly what I was looking for."
 


  

Marilyn

12 Jul 2008 6:05pm

"Thank you, thank you, thank you! This is what I have been looking for, clear concise understandable information."
 


  

Susan B

10 Aug 2008 10:29pm

"Simple just as i like thank you great just what i needed"
 


  

Graybeard

14 Sep 2008 11:46am

"This is what I have been searching for, lucky for me I was given the link in a forum... great explanation! (I can see clearly now the rain has gone...) thank you"
 


  

image submission

06 Nov 2008 4:15pm

"what does this mean: Images should be 1024 pixels on the longest side at 72DPI. This is a submission guide line for a digital photo contest Thanks!

[Reply from Robert Giordano]
That's actually kind of ridiculous because they're giving you pixel dimensions. 1024 pixels is 1024 pixels at ANY DPI!"
 


  

Sean

06 Jan 2009 9:52am

"Well done. It took ages to find a website the explained all about dpi and ppi in simple terms. Your charts are brilliant. Pity the camera people don't tell the truth about print sizes. Thank You."
 


  

Thank you for a great post!

08 Mar 2009 11:21am

"Just want to say thank you, your post gives me all the info that I'm searching for."
 


  

Thank you =)

01 Apr 2009 2:56pm

"Awesome job at explaining the difference between everything! Been doing photography for 15 yrs and the last 10 of those digital. Never found anything that explained very clearly everything as you did here. I very much appreciate it! Thanks again ~Jen Martinez"
 


  

Brilliant

15 Apr 2009 1:11am

"this is such a tricky info shared in such a simple way i love the way you explain literally thank you indeed"
 


  

docdick

31 May 2009 6:59am

"An honourable man remained true and loyal to his wife Lorraine, although his true love was Clearly. Lorraine finally passed away and shortly after Lorraine's funeral he sang this song. "I CAN SEE CLEARLY NOW, LORRAINE IS GONE". Thank you! I can see clearly now also. The best explanation yet. Dick Kane"
 


  

Uncle Carbunkle

12 Jun 2009 9:53am

"I've tryed to explain these concepts to clients and would be digital camera owners for years. Their eyes simply glaze over (ppi, dpi, 72 ppi native resolution, 300 dpi reproduction resolution . . . oops there they go!). In future I'll just send them here. Very well presented. A goldmine for the digital age. One tip, Postscript rasterizes 305.9 dpi faster and better than 300."
 

  

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