DPI

B
Posted By
Bob
Jun 5, 2005
Views
512
Replies
3
Status
Closed
If I have to make a document in 640×480 in 150 DPI and 1280×1024 in 72 DPI. Is my understanding of DP correct?

640×480 = 8.889" x 6.667" = 59.262963 square inches. 1280×1024 = 17.778" x 14.222" = 252.838716 square inches.

589.262963 x 150DPI = 88389.44445
252.83871 x 72DPI = 18204.387552

The 640×480 has more pixels and should therefore be the "original" that I blow up to 1280×1024?
Related Tags
dpi

Master Retouching Hair

Learn how to rescue details, remove flyaways, add volume, and enhance the definition of hair in any photo. We break down every tool and technique in Photoshop to get picture-perfect hair, every time.

E
edjh
Jun 6, 2005
Bob wrote:
If I have to make a document in 640×480 in 150 DPI and 1280×1024 in 72 DPI. Is my understanding of DP correct?

640×480 = 8.889" x 6.667" = 59.262963 square inches. 1280×1024 = 17.778" x 14.222" = 252.838716 square inches.
589.262963 x 150DPI = 88389.44445
252.83871 x 72DPI = 18204.387552

The 640×480 has more pixels and should therefore be the "original" that I blow up to 1280×1024?

Forget about dpi and inches. They are irrelevant until printing time. What counts is the NUMBER OF PIXELS. Are you trying to say that a 640×480 pixel document has more pixels than a 1280×1024 pixel document? Think about it.

—
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html
B
bH
Jun 6, 2005
Bob wrote:
If I have to make a document in 640×480 in 150 DPI and 1280×1024 in 72 DPI. Is my understanding of DP correct?

640×480 = 8.889" x 6.667" = 59.262963 square inches. 1280×1024 = 17.778" x 14.222" = 252.838716 square inches.
589.262963 x 150DPI = 88389.44445
252.83871 x 72DPI = 18204.387552

The 640×480 has more pixels and should therefore be the "original" that I blow up to 1280×1024?

640×480 = 307,200 pixels of data
1280×1024 = 1,310,720 pixels of data which is a little more than 4 times the amount of pixels.

If the 640×480 document is printed at 150 DPI, it means that when you print the image 150 pixels in the x resolution will print in 1" and the same for the y resolution. More correctly, 150×150 pixels in a 1" x 1" block, thus 22,500 pixels in 1 square inch … thus the size of the printed image will be 4.26" x 3.2"… (640/150 x 480/150)…

The 1280×1024 document at 72DPI will print at 17.7" x 14.2"(1280/72 x 1024/72)… the recorded image data is greater, the printout is larger, but the print quality will be less since there are less pixels per inch.

bH
T
Tacit
Jun 6, 2005
In article <d802nn$n3e$>, Bob
wrote:

640×480 = 8.889" x 6.667" = 59.262963 square inches.

No, 640×480 is 640 pixels by 480 pixels. The number of "inches" depends on the resolution. 640×480 at 640 pixels per inch is 1 inch wide. 640×480 at 320 pixels per inch is 2 inches wide. And so on.

640×480 has FEWER pixels than 1280×1024. 640×480 means 640 pixels wide and 480 pixels high. 1280×1024 means 1,280 pixels wide and 1,024 pixels high.

—
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

How to Improve Photoshop Performance

Learn how to optimize Photoshop for maximum speed, troubleshoot common issues, and keep your projects organized so that you can work faster than ever before!

Related Discussion Topics

Nice and short text about related topics in discussion sections