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Why scanners use dpi instead of ppi

Sahar
Apprentice

WHY do scanners use dpi as resolution setting? dpi (dot-per-inch) refers to dots of ink in the printers.

I think scanners should use ppi (pixel-per-inch) since they are generating pixels!This is a question that sofar no experts has an answer for! I hope someone here has.

let's say i created an illustration in photoshop with size A4 and resolution 150 ppi. then i set my printer on 600 dpi and get a print of the same size(A4) now every pixel of the image has been covered b 4 drops of ink (600/150=4).

Now i want to scan this image. since scanner will generate pixels i think the setting should be ppi but it isn't so why is that!
what is the dots standing for? some print experts think this is a mispronunciation of pixel and some think this mean the scanner should assume how many dots of inks per inch of image has been used and translate that into pixels or generate that many pixels per inch.

The optical resolution of a scanner is the resolving power of scanner which is a measurement of how much information the scanner can resolve while digitizing an image. so, I personally believe since there is no ink involved and scanner is generating pixels, we have to see ppi in the setting and not dpi. what do you think?

1 REPLY 1

rs-eos
Authority

Probably a hold-over from the early days.  You can effectively treat the two values as being the same thing.  Both denote the amount of detail you'll get per inch.

For something completely different, the industry unfortunately uses "dots" insteads of pixels for camera displays.  No idea why.  e.g. on the EOS C70, the viewfinder has 2,760,000 dots.  Here, a single dot is an individual component of an RGB pixel.  So you need to divide by three.  The C70's screen is thus 1280 x 720 or 921,600 pixels.

--
Ricky

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