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Dig Camera MegaPixel size vs Print Size

Greg Tomas , Nov 25, 2003; 10:15 p.m.

Hi all,

Can anyone tell me the MP size of a digital camera needed to make a good 16X20 print on a photo minilab system. I know 3.1mp will make 8X10, and 4mp is good for 11X14. But how about 16X20 which is my standard film print size.

Responses

Blake Wallen , Nov 25, 2003; 11:07 p.m.

the quialty of the camera will make a big differance as well. i have a fuji s2 which is 6.1 mp and it will print perfect 16x20 and even great 20x30, but i have a Sony F717 which is 5 mp and the 8x10's from it are not even close to flim 8x10's so i would say 6mp is enough if it is a good camera.

Jesper de Jong , Nov 26, 2003; 09:52 a.m.

This has been discussed many times before in this forum and the Digital Darkroom forum, so if you search in there you might find some useful information.

There is no exact rule that says "for this print size, you need ... megapixels". The answer depends on what you think is "good enough". Based on the numbers you give, you could do some calculations:

If you print a 3.1 MP image at 8 x 10 inches, how many pixels per inch do you get? Let's suppose your 3.1 MP image has a size of 2033 x 1525 pixels. Looking at the long direction, if you spread out 2033 pixels over 10 inches you're printing at 2033 / 10 = about 200 pixels per inch.

Now 16 x 20. The long side is 20 inches. If you want to print at this size with 200 pixels per inch, you will need 16 x 200 x 20 x 200 = 12.8 megapixels!

That means you need a REALLY expensive camera such as the Canon 1Ds (11.1 MP) or Kodak 14n (14 MP). BUT... you can probably get away with less resolution, because most of the time you will be looking at your 16 x 20 photo from a larger distance.

Glen Peterson , Nov 26, 2003; 05:54 p.m.

MP's on digital cameras are not as important as some think. I once printed a 1.4mp image from an old digital camera(Olympus d-600) at 10x13, and it was beautiful, and gets many compliments hanging on my wall. Even though it was printed at abt. 97dpi, the only way you can tell its digital is by really looking close at the cats whiskers. I have also printed 8x10 pictures from 4mp cameras that look like hell... Many will say that prints REQUIRE 300dpi, but I don't really buy that, it seems that every picture, as well as camera will give different results. Besides no one is really going to be looking at you prints through a loup.

Eric "damn those seagulls" Cantona , Nov 26, 2003; 07:00 p.m.

Assuming you're referring to the common compact-digicam sensor size of 1/1.8" you may find 16x20s of quality very difficult to achieve, whether 4,5 or even 8MP. This type of camera sensor struggles beyond 11x14, some say 8x10, but it’s all in your perspective and personal standards I guess.

Differences in sensor (and hence photosite) size mean “all MPs are not created equal”. So, a 6MP CMOS on a 300d will disproportionately outperform the 5MP, far smaller G5 sensor. If you want 16x20s, really you should be looking at this sensor type. The 300d/digital rebel is a steal for you yanks (in the UK we have to pay 50% more) so there is no excuse!

Steve Muntz , Nov 26, 2003; 11:09 p.m.

Like everyone says, there's no absolute number required. It'll probably take less than you think. I recently had a 24x36 made from an image I took with my Fuji S2. I shot it in jpeg mode, 12mp interpolated.

A book I have says that you can upsize an image in Photoshop by 10% with no loss of detail. If you want a big print, upsize it 10% several times. I did this 10 or so times and got a 150mb file which gave me 24x36 at 240 dpi. Bottom line - print looks great. If you don't make 16x20's very often, this idea might be worth considering.

Curt von Diest , Nov 27, 2003; 07:20 p.m.

Certainly stair-stepping your interpolation in photoshop (10%+10%+10% etc) will give you better results than doing it in one jump and better results than printing your file at a lower resolution. However, I've found having my service burrow interpolate (or res-up) a digital file to be far, far superior. I took an un-cropped file from my D100 (6.1 MP) which was captured in RAW mode and edited in PS, saved as a TIFF. The print size at 300ppi was about 7x10". I had my lab interpolate it and print it on Fuji Crystal Archive on their LightJet printer and the results knocked my socks off. Staring eyeball-to-print I can see no pixilation. Next test... 20x24... and I bet it will also be great.

- CURT - St Louis Photographer

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