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Old May 5, 2004, 11:10 PM   #1
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It's been my understanding that a 2 mp can do a 4x6 or 5x7 print, a 3 mp would 8 x 10. I've been seeing reviews and camera descriptions where they've stated that a 3 mp can do a 20 x 30 inch poster. (believe this one was a Fuji product) Have also seen a few other reviews where the print size is well beyond what I had expected. What's the story on these claims,,,,, is it just marketing hype or is there substance to this?

Thanks if you help clarify this.....Derreck
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Old May 5, 2004, 11:18 PM   #2
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lol.....a .4 MP camera "could" print a 20x30.....it would look terrible though....quality wise....lol

my point is...any MP "could" print that big....but not necessarily with good quality...

hope this helps....

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Old May 6, 2004, 8:03 AM   #3
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I look at the x and y dimensions of the image in pixels and divide by 300. That will give you the dimenions of a decent print quality in inches. You can use software to interpolate the file to a larger size and resulting larger print size, or you could reduce the print quality down to (say) 150, but I'd suggest sticking with a smaller, sharper print.

Having experimented with larger sizes I now just print at A5.

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Old May 6, 2004, 9:48 AM   #4
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As a general rule of thumb, you want at least 150 Pixels Per Inch (PPI) for a print. Although, at larger sizes, you tend to view a print from further away, so you can "get by" with less.

Subject Type is also a factor. I've printed stunning 8x10" photos from cropped 2 megapixel images (interpolating back up after cropping). I've also seen some pretty bad ones. Subjects at closer ranges, with less detail (i.e., Portraits) tend to print much better at larger sizes, compared to something with more detail (like a landscape with lots of foilage).

Here is a handy chart that you may want to use a general guide. Personally, I can see a marked difference in quality going from 150 PPI to 200PPI. However, I cannot tell the difference going from 200PPI to 300PPI (withoutVERY close inspection). Of course, this may be dependent on the printer used, too. Inkjets are more "forgiving" -- since many printer software driverscan "enhance" (or interpolate) the image before sending it to the printer.


Note that they are using DPI in the chart (when the correct term should be PPI). Even though a printer may be capable of very high DPI, you must still have sufficient pixel detail (PPI - Pixels Per Inch) for a good quality print.

Because every detail of a photo is magnified at larger print sizes, defects (noise, JPEG Artifacts, etc.) tend to be more noticeable. So, it's best to have a very clean image to start with, too.

Graham mentioned interpolation. Depending on the printer (some printer drivers automatically "rez up" an image), you will get pixelation if you go too much below 150PPI (on an inkject), or 300PPI (on some dye sub printers).

Interpolation adds pixels to an image (based on the values of adjacent pixels). However, it cannot increase the detail captured. It is useful for preventing pixelation, so it allows you to make much larger prints.

Personally, I use Irfanview's "Lanczos" algorithm for upsizing my images. After cropping a photo, I'll typically resize back up to 300 Pixels Per Inch before printing. For an 8x10" print, this works out to 3000 x 2400 pixels (300 ppi x 10 inches =3000 pixels; 300 ppi x 8 inches = 2400 pixels), or 7.2 Megapixels.

You can download it free from http://www.irfanview.com (make sure to download the free plug-in's, too).

BTW, it takes 4 times the resolution, for the same amount of detail in pixels per inch, each time you double the print size (because resolution is composed of width x height).

Likewise, you can't crop as much as you think, either. If you crop a photo to look like you used twice as much optical zoom, you end up with an image that's only 1/4 the original resolution.

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Old May 6, 2004, 11:31 AM   #5
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It depends on what you want the print for, and how fussy you are and how fussy the viewers are likely to be, and how far away they'll be standing when they make their judgement.

Any photo will be grainy or fuzzy if you enlarge it enough. You should do some experiments for yourself (I seem to keep saying this on this bulletin board). Take a good image and blow it (or bits of it as you move to bigger enlargements) up to various sizes, print them, stick them on a wall, walk to and fro, and decide what you can tolerate, or what your target viewerpersons might tolerate in terms of unsharpness.

Because of camera shake, depth of field, etc., I think that 5Mpixel imagesare for practical purposes very similar to 35mmunless you're very fussy. There's usually no point in printing better than 300dpi, and much less will usually do.

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Old May 6, 2004, 11:13 PM   #6
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Thanks very much for your opinions and information, it's all very useful and helping me to narrow down my choice. Appreciated the link to the charts.

thanks again,, Derreck
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Old May 20, 2004, 8:16 AM   #7
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I printed many 10 by 8s with my 1.3 megapixel camera. The quality was very good.
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