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Here is a great question from a #Cazillion on DPI.  In my video I explain how it works and why DPI/PPI really don't matter when exporting your images.

Subject: resolution/printing

To: Gregory Cazillo

Hey Greg, I am new to printing and I am having a problem regarding resolution/printing. Some of my pics say x and y resolution 72 dpi and a pic taken minutes later will say 300 dpi.(I am getting this from the exif info in flickr). Also, at this time i have only edited in iphoto.

1. How do I set my resolution for the best possible quality?
2. How does dpi relate to printing size and quality?
3. How/Can I print large prints ex. 20x30 with my D90

Thanks for all your help....


Definitions from Wikipedia:

PPI: Pixels per inch (PPI) or pixel density is a measurement of the resolution of devices in various contexts; typically computer displays, image scanners, and digital camera image sensors.

DPI: DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain; the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media.

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+1 # John Dodd 2012-04-03 13:02
Thanks Greg!!! Great bit of useful information!!
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0 # Roger 2012-04-03 17:39
I have seen several charts regarding how big a print you can make with how many megapixil camera. So now I am really comfused! Just trying to understand!!!If you only have 2 megapixils to work with --then is the software interpolating and adding data? If so that seems like lost quality? Just trying to understand!!
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0 # Gregory Cazillo 2012-04-04 09:56
There are limitations, don't get me wrong. I upresed the files to get big prints from my 2mp camera. The main thing most photographers need to know is don't worry about ppi/dpi on the web or for normal prints. You only need to be concerned with the pixel dimensions and for the most part the bigger your dimensions the bigger your prints can be.
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0 # Mike 2012-04-05 10:47
So lets say its a 16x20 print. If you want to print that at 300dpi you need 300*20=60000 pixels (on the long edge) to print.

I have a D5000 with a 12MP sensor which produces 4288pixel images (on the long edge). Doing the math I could print a 14" image at 300dpi natively. Or I could print a 20" image at 214dpi natively (no up-rezing). However if I wanted to print the 20" image at 300dpi I would have to up-res from 4288 to 6000 pixels. Am I understanding that correctly?
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0 # Gregory Cazillo 2012-04-05 16:13
First dpi are dots of ink on paper and have nothing to do with pixels. Second 12MP is plenty of resolution to print 40x60 or larger images without noticeable issues (with good exposure and no cropping). PPI/DPI have nothing to do with it, its all about the size of the image & there is no need to upres especially for a small 20" print.

Just to review: don't worry about your DPI or PPI!
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0 # Roger 2012-04-06 22:41
Like I said____ I can show you many charts showing the relationship between megapixels and print size. Without uprezing how do you make a good print? TRYING TO UNDERSTAND!!!!
I want to see your 40 X 60 from a 2MP camera!!!! Then I will believe it!!!!PLEASE SHOW EXAMPLES!!! Man I believed in you untill this!!!!


common print size (rougly 300dpi)

2 MP


10x13cm / 4x6"

3 MP


13x18cm / 5x7"

4 MP

2400 x 1600

18x23cm / 6x8"

6 MP


20x30cm / 7x10"

8 MP


30x40cm / 10x14"

12 MP - better more


40x60cm / 16x24"
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+1 # Mike 2012-04-07 09:17
Do you really need to print a 40x60 at 300dpi? If a picture is 5 feet on the long edge are you going to be standing close enough to notice a picture printed at 300dpi vs. say 200dpi?
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0 # Peggy 2012-10-25 10:46
Hi Greg - I am new to digital photography, having worked in film until recently. I have a client who would like a CD of images to share with family & friends on Facebook and email. I have Lightroom 4 - at what settings would you recommend my exporting images to be burned onto a CD that would make the images only suitable for viewing online and not yield decent prints, if attempted? thanks
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0 # Gregory Cazillo 2012-10-31 11:28
500-600px on the long side, jpeg file at about 50% compression will be fine.
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0 # Gregory Cazillo 2012-10-31 11:29
And don't forget to set the profile to sRGB.
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