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01/10/2005 05:29:25 PM · #1 |
| Ok, I've got a question that I couldn't find the answer to in the forums, mainly because I don't really know what to look for. Here's the question. When I take a photo with my 3 mp point and shoot, even on the highest quality, it always comes up as 72 dpi in photoshop. What do you need in terms of megapixels in order to get printable 300dpi (or higher) images, where you don't see jpeg artifacts and pixelation? You can't just change the resolution in Photoshop right? It has to be 300dpi to begin with, if I'm not mistaken. |
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01/10/2005 05:46:50 PM · #2 |
Some cameras are only capable of rendering a jpeg at 72 dpi.
Photoshop does have the ability to interpret and remember that you wish to use 300dpi, but it may have to do some serious interpolation to the original to get it there and that can cause an awful lot of artifacts and ugly pixels.
Message edited by author 2005-01-10 17:47:41.
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01/10/2005 05:49:59 PM · #3 |
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01/10/2005 05:50:37 PM · #4 |
Imagine your photos as having 2000 little squares at long side and 1500 squares at short side.
When you do the math 2000 X 1500 = 3,000,000 or 3MegaPixels.
Now ,how big you want the prints to be?
If you divide 2000 available pixels with 300 DPI ,the photo size will be 6-7 inches at the long side.
If you print at 150 DPI ,divide 2000 with 150 and photo size will be 13.3 inches at the long side.
Message edited by author 2005-01-10 17:51:13. |
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01/10/2005 05:51:15 PM · #5 |
DPI is just a reference number. It has nothing to do with how many pixels an image contains.
A 6mp camera shoots at 3000x2000 pixels, no matter what the DPI resolution is.
3000x2000 pixels =
300dpi @ 10x6.66" in print
150dpi @ 20x13.33" in print
72dpi @ 41.6x27.7" in print
No matter how you dice it up, you still have a 3000x2000 pixel image. Programs like photoshop tend to show the dpi size as 72 by default. When you look at the image dimensions in inches associated with that number, you will see that it is a large image.
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01/10/2005 05:53:22 PM · #6 |
If you're printing at home 150dpi is usually plenty. You need higher resolution if you are getting your prints done elsewhere.
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01/10/2005 05:59:07 PM · #7 |
I usually shoot for 300-320dpi when I have prints made
If I can't get it I usually use cubic upsampling in small portions to get the needed resolution.
This allows me to order crystal clear 11x14 prints at 300dpi |
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01/10/2005 06:21:26 PM · #8 |
There are several fine points I would like to make.
JPG artifacts will only show up if the image has been overly compressed, this is true no matter how much you blow up the image.
Pixelation is not a problem when using most printer drivers, they will tend to interpolate the pixels they don’t have.
So as you blow up the photo it should simply have softer edges and look blurrier.
Not all pixels are the same, the 8 MP from my Sony F828 will not print as sharp a photo as the 8 MP from by wife’s 20D.
And just to restate what others have said, the DPI that your camera puts on the photo has no real meaning at all.
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01/10/2005 07:53:16 PM · #9 |
Here is how you can use Photoshop to find out how big a print can be made from your photo when it is printed at 300 dpi.
Open any image in Photoshop.
Under the "Image" menu select "Image Size"
Make sure the "Resample Image is NOT checked.
Change the "Resolution" to 300 pixels.
The two dimensions above that will give you the maximum sizes for that image.
To sell larger prints you have the option to "upsize" the image, there is a very great tutorial on that subject. This upsize technique will allow you to sell larger prints if the quality is still there when you have made the image bigger.
Message edited by author 2005-01-10 19:58:19. |
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01/10/2005 10:53:54 PM · #10 |
see //www.scantips.com/ for a complete discussion on DPI, LPI and the like.
DPI is for PRINTING only. The screen resolution has no I (as in inches). Fuji cameras default to 72dpi, my Rebel to 300dpi, my buddy's Nikon 2200 i think is 200 dpi.
It matters not, unil you print. If you ship this pics to a photolab, they will make them the size you specifiy (4x6, 5x7, etc) regardless of the DPI setting, be it jpg or tiff, 200k or 3Mb file.
For best results, you want 250 pixles of size for every inch of final print (or more pixels is fine)
For for a 4x6, you want a file of 1000x1500 pixels or there abouts.
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