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Old Aug 9, 2010, 10:56 PM   #1
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Default How big a print can I go with a...

18mp T2i? This may be more involved than a pixels-per-inch argument. I have shots that are, dare I say, tack sharp in an 8x10 print with my kit lens. From a practical level, how far can I expect to go with the camera without L series lenses?

Expanding a little, what sort of dpi am I needing?
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Old Aug 9, 2010, 11:42 PM   #2
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set it to 400dpi, and you can print poster size. With the 15mp camera, I printed 24x36 without problems.
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Old Aug 10, 2010, 1:56 AM   #3
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The Canon 18-55 IS kit lens is quite good, and 18MP is a lot.

A computer screen generally has a resolution of 96 dpi, newspapers are happy with 200 dpi, but magazines generally won't use anything less that 600 dpi.

Generally, the typical viewing distance for an image hanging on a wall is approximately equal to the diagonal measurement of the image. That is, the larger the image, the farther away a viewer will choose to stand when looking at it. Therefore, the resolution of a large image really doesn't matter, within reason. For instance, if you're going to use an image from your T2i to create a mural, people are likely to observe some portion of the image from closer than they would when looking at the entire image, if indeed, observing the entire image is even possible, given the size and shape of the room.

If you want your wall hangings to have the same resolution as images in a magazine, that 18MP is going to slip away pretty quickly, and Canon's 'L' series lenses are as much about durability as optical performance. There are no hard, fast numbers for what you're talking about, and remember that the entire Impressionist Era seems to have done well with resolutions on the order of 10 dpi or so.
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Old Aug 10, 2010, 7:09 AM   #4
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Quote:
Originally Posted by iowa_jim View Post
18mp T2i? This may be more involved than a pixels-per-inch argument. I have shots that are, dare I say, tack sharp in an 8x10 print with my kit lens. From a practical level, how far can I expect to go with the camera without L series lenses?

Expanding a little, what sort of dpi am I needing?

HUGE!!! I have had some of my images blown up to around 8 x 12 feet at the International Festival of Fashion Photography in Cannes France shot with a 10 MP camera.

All depends on viewing distance and Dpi output.
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Old Aug 10, 2010, 10:02 PM   #5
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Wow, that is big, great picture too.
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Old Aug 11, 2010, 6:05 AM   #6
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Thanks for the help! I don't understand the correlation between the pixel rating of a camera and the dpi figure. Is 400 dpi indicating 400 dots per square inch?

Doing the math that way,
18,000,000 mp image / 400 dpi = 45,000 square inches of print, or an 18'x18' print

If it is 400 dots per lineal inch, it is then 400x400 dots per square inch, giving us:

18,000,000 mp image / (400x400) = 112 square inches or a 1'x1' print
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Old Aug 11, 2010, 7:31 AM   #7
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The dots per inch is a linear measurement, based on the sensor pixels, so a sensor of 4000x6000 pixels (24MP) would give a print of 10"x15" at 400dpi printing.
Usually, 300dpi is considered about the most needed for printing - without a loupe, most people will not see any improvement if the print density is higher.

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Old Aug 11, 2010, 8:22 AM   #8
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Don't worry about dpi. That's an absolute measure of resolution. What's important is the viewing distance for a person with normal vision. As the viewing distance increases, the resolution can decrease. For instance, normal (20/20, or 6/6 in metric) vision can distinguish detail as small as 1 arc minute. That works out to be about 180 dpi at a viewing distance of 2.5 feet, 90 dpi at 5 feet, 45 dpi at 10 feet, and 22 dpi at 20 feet. And remember that people generally choose a viewing distance that is equal to the diagonal of the image size. That means that a viewing distance of 2.5 feet would be appropriate for a print as large as 17x25.5. At 180 dpi, that would require an image with a resolution of 4590x3060. At 5184x3456, the T2i beats that in spades! And remember that the brain always fills in detail where the eye has only a hint. So you could even get away with a fair amount of cropping, yet still produce images that are more than good enough to hang on a wall.
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Old Aug 11, 2010, 12:37 PM   #9
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Sweet! So my 5184x3456 yields, at 300 dpi, 17"x11". Or 22"x34" at 150dpi. Then, for my more usual 8x10 work I have roughly 500 dpi.

Thanks for all the help!

Jim, in Iowa
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Old Aug 12, 2010, 2:32 AM   #10
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Almost anything small or distant enough can look good. I've shot 912x1216 pixel images with a 1mpx digicam and blown them up to 12x16 inches, diagonal=20 inches. (That's 76 DPI, a bit better than web screens.) Massaged a little and viewed from beyond 30 inches, they look photographic. (I've printed such larger too, but as posterizations.) Presentation is vital. Matted and glassed and framed, a picture looks larger, and rough edges fade into insignificance. Textured paper or fabric also trivializes jaggies and noise. And if all else fails, hang it in a dark corner.
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