Resolution needed for printing

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What resolution digital camera do I need to "blow up" pics and print them as 8x10's on an HP PhotoSmart printer? I print quite a few 4x6's but the printer is capable of printing 8x10 glossies and I would like to take pics of my grandkids and print 8x10's without pixilation problems. Would 1280x1024 (like an Olympus D600L) suffice or would I need to go to 1600x1200 (like a Nikon Coolpix 700)? Any help would be greatly appreciated.........Thanks......

-- Ralph McLaughlin (kanman@sound.net), May 03, 1999

Answers

Hi Ralph,

It seems to me that what you're really asking is how many pixels do I need to capture for each inch of an image I want to print? If you're already able to print good 4x6" pictures and you know how many pixels your camera can capture then you can figure out what the ratio that you're already using works out to and use it to predict how many pixels you'll need to capture in order to print a larger image.

Basically what you need to do is determine how many pixels wide your current images are and divide that by the width of your image in inches. That tells you how many pixels you're printing across each inch with your current settings. If you multiply that number by the width of an image you'd like in inches your answer will be the number of pixels you need to capture to be able to print the image that large with the same number of pixels per inch as you were happy with before.

For example:

Camera: Toshiba PDR-M1 Resolution: 640x480 Print size: 5x4"

640/5 = 128 pixels per inch. or 480/4 = 120 pixels per inch. I'd stick with the higher number and use 128 PPI as my lower limit.

Now if I wanted to print a 10x8" at the same ratio of pixels per inch I'd use what I learned above and say that I need 128 pixels for each inch of print. So 10"x128ppi= 1280 and 8"x128ppi= 1024. Pretty convenient since the PDR-M1 will also take 1280x1024 shots. (Nah, I didn't fudge the numbers, they just work out that way. :-) )

A couple of other things to remember:

Your printer may need more or less dots per inch to produce a decent image. Don't use 128ppi as your rule, do the math following the example above to get the proper ratio for your situation.

Just because your images look good at the ratio you're using to print them currently doesn't mean that they will look worse with a reasonably lower resolution on your printer. The only way to tell is to see just how large you can print a current image and get an acceptable result and use that data to set your worst case limits. If you always choose an image size that yields a PPI ratio slightly greater than or equal to one that you know works you'll always err on the side of caution. If you try to print too many pixels per inch your printer may not be able to produce the full range of colors necessary for your image so don't overdo it.

I hope that makes some sense. Good luck.

-- Gerald M. Payne (gmp@francorp.francomm.com), May 03, 1999.


The short answer is yes: The D600L makes a fine 8x10.

-- Ben Jackson (ben@ben.com), May 04, 1999.

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