Resolution and DPI - what is the difference?

page 1 of 1 5 total items

Alex204

Seeking Rakuen

Cancel

When creating a new file in photoshop it asks for the pixel dimentions and a resolution (or DPI). What exactly does the DPI setting do if i have already defined how many pixels are in the image - is there something smaller than a pixel? My only theory is that it photoshop only looks at this value if you set the size in cm or inches or something like that. If someone could explain this one i would be a great help!

Signature
	Image
"Rules are there to make you think before you break them."

levezzali

levezzali

Purge Existence

Cancel

DPI is usually the quality of your image, like for internet, the normal seting is just 72 dpi, but if if you print that sort of resolution the result will be catastrofic, so, dpi is also used for printing specifications (for a good print, the quality should be around 300 dpi)
Also, larger dpi settings make a much better quality files, such as scans and wall papers, dpi also makes the file larger in space... well, I hope if I didn't let you more confused!

Purified Existence of a Lost Soul

... ok ... I am not a that serious person !! XD

rayearth

rayearth

[ The Real Gouf ]

Cancel

yup, the terms dpi are most commonly used in printer specification, the higher the number, the better its quality.

btw I think dpi stands for dot per inch :)

Cancel

uh..... i must correct you. dpi has nothing to do with the quality of an image, you can create perfect looking wallpapers with a setting of 10 dpi!

dpi is dots per inch. So it is the connection between the size of an image in pixel and its size in inches. An example:
You have an image of 3000x3000 pixel. You declare it to be 300 dpi. so when you print it it will be 10 inch by 10 inches large. If you declare the same image to be 150 dpi and print it, it will be 20x20 inches in size. each pixel will be printed double sized.
dpi has no impact on the quality and most printers can override the dpi setting of the image for printing.
In photoshop you can create an image either by giving its size in inches or pixel. dpi is used for conversion between pixel and inches

As long as you dont print, dpi is mostly meaningless, Often you use a 72 dpi setting because it gives you an rough idea how large (in inches) the image will be when displayed on a monitor. (on a monitor 72 pixels are very roughly 1 inch wide) But most software ignores the dpi number altogether

This changes if you want to print images and need to know how large your printing will be. Lets say you want to create a cd cover and know how big a cd is (x inches by y inches) Problem is that computers always store images by pixels and that a computer pixel has no real size. So you create an image x inches by y inches and set it to 300 dpi (good quality photo printing) and photoshop computes from these values how many pixels the image has.
creating images with higher resolutions than 300 dpi is pretty much only a waste of disk space.

And now for something else: printers and dpi. It is true that the dpi spec of printers is a rough indicator for printing quality. But a very rough indicator only! A good 300 dpi thermosublimination printer prints better photos than a bad 1200 dpi inkjet printer.

  • Feb 09, 2005

Alex204

Seeking Rakuen

Cancel

Ok, i get it now. dpi only takes effect in the real world. In terms of walling it makes no difference. Thanks logotomie for clearing that one up!

Signature
	Image
"Rules are there to make you think before you break them."

page 1 of 1 5 total items

Back to Computers & Internet | Active Threads | Forum Index

Only members can post replies, please register.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read more.