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10/11/2006 05:15:35 PM · #1 |
| I am trying to resize a picture in Photoshop (CS2). The final required file should be 600 pixels (wide or long) and 100 dpi. I don't understand what DPI means, well I do understand that it means dots per inch and it's how many dots per inch the printer puts on the paper, but is it the same as pixels per inch? If not, how do I make a file a certain DPI size in Photoshop. I'd be grateful to anyone who can explain this to me. Thanks in advance. |
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10/11/2006 05:18:32 PM · #2 |
It is confusing. Just make you outside dimensions how you want them (say 600x600 pixels) Then don't worry about the DPI. Actually DPI is a printing term, the actual term is PPI (Pixels Per Inch) and if you set your dimensions in pixels, you don't have to worry about the DPI or PPI.
You can set you size in inches and then specify the DPI or PPI. For instance, when printing to an inkjet printer you should set your dimensions to the paper size (8x10) then set the DPI to the printer specs, usually 240 DPI.
If you do this, notice that when you change the DPI, the outside deminsions also change (if resample has been turned off). This means that all these measurements are relative to each other.
Message edited by author 2006-10-11 17:21:32.
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10/11/2006 06:10:35 PM · #3 |
| OK thanks. So it is the same as PPI. That's what I thought but the resulting file was so small I got confused. Thanks that clears it up. Appreciate your quick response. |
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10/17/2006 09:06:40 PM · #4 |
DPI is often wrongly used in place of PPI. You use PPI in digital work and DPI for print work. Photoshop only lists it as DPI for some reason although they should know better. If you want to read some good articles about the difference these are pretty good:
//www.tildefrugal.net/photo/dpi.php
//www.design215.com/toolbox/print_guide.php
I own an online magazine for Architectural Visualization Artists and this same topic comes up quite often. I wrote a short article about it on our fourms which you can access here:
//www.cgarchitect.com/vb/5759-printing-resolution-size-dpi-ppi.html
Hope that helps.
Cheers,
Jeff
Message edited by author 2006-10-17 21:10:47. |
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10/17/2006 09:37:29 PM · #5 |
PPI act as a tag in your file that tell your printer how big to print your image. DPI is the actual number of ink dots on paper.
These 2 numbers are different because a printer actually print more than one dot for each pixels in your file.
Let's take a epson R1800 for example. The resolution is (Width)2880DPI x (Heigth)1440DPI. let's say you print a file that is 360PPI (width and height). The printer will then print 32 DOTS for each pixels in your file.
The formula: (2880/360) * (1440/360) = 32
If you change the dpi in photoshop to 180PPI, your file will print with twice the width and twice the height with the same amount of pixels. You changed the PPI but the printer DPI is still the same. now the printer will print 128 dots for each pixels in your file. Every pixels will be four times as big and you will have half the resolution.
The formula: (2880/180) * (1440/180) = 128
Message edited by author 2006-10-17 21:43:09.
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10/20/2006 03:58:01 AM · #6 |
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