This actaully answers your question, Doug! Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt
-----Oprindelig meddelelse----- Fra: Jens Bladt [mailto:[EMAIL PROTECTED] Sendt: 17. november 2004 19:11 Til: [EMAIL PROTECTED] Emne: RE: Pixel Puzzlement I have read at www.shortcources.com that a pixel (in an image) does not have a size - it's a code in a computer, not a real physical thing. I believe that's what you are saying as well. How big it's seen depends on the ppi-resolution - how you print or see it on a screen. But that's not quite true: On the camera sensor the photdiodes (pixels) really have a size. In a * ist D 3008 pixels is sitting on an app. 24mm wide sensor. This means the original "size" of a pixel is something like 24mm/3008 = 0,008 mm. So, the resolution is close to 3200 ppi (pixel pr. inch) :-) Every time you enlarge the image, the ppi will fall (provided there's no interpolation). Making the printer do the job, just means that the printer/printer driver does the interpolation to make the image fit the sheet of paper at a chosen ppi. Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt -----Oprindelig meddelelse----- Fra: Sam Jost [mailto:[EMAIL PROTECTED] Sendt: 17. november 2004 18:47 Til: [EMAIL PROTECTED] Emne: Re: Pixel Puzzlement A pixel is as large as you print it. For me an image got pixels. And depending on the size I'm showing it at I'll get different ppi ppi=pixel/size I don't care at all about ppi. When I order a print I order a specific size, and no matter what ppi values I got in my image I'll get that size. Same with showing on monitor - I'll just show the picture at some specific size and don't care about ppi. Most image editing programs work well with this attitude - if they offer a ppi setting they mostly just store the value you enter and don't do anything with it. The only exception I know about is Photoshop which annoyed me mightily by resizing my picture when I changed the ppi setting. But since most use PS I met a lot of people who change ppi settings for resizing pictures. Very confusing way to resize a picture in my book, but hey, thats just me. ah well, enough disgression. About your second example, the same picture scanned with 1000ppi instead of 100ppi will have lots more (10^2) pixels, and if you print both at the same size the 1000ppi-pixels will be smaller. Just more pixel crammed into the same space, as you yourself already noted, yes. Sam ----- Original Message ----- From: "Shel Belinkoff" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, November 17, 2004 6:09 PM Subject: Pixel Puzzlement > I've been pondering this perplexing pixel problem for a while, and thought > that someone here may have the answer: How large is a pixel? > > What I mean is this. If there's an image that has a resolution of 72ppi, > typical for web presentation, and another image, from a scanned version of > the same source, of 4000ppi, are the pixels in each image the same size? > It doesn't seem possible, since if 72 pixels make up an inch each > individual pixel would seem to be larger than if there were 4000 pixels in > the same space. But then, if an image has more pixels per inch than > another image, why is the image larger. Example: one scans a photo @ > 100ppi and again @ 1000ppi, the 1000ppi scan has greater dimensions, but, > it seems to me, it's just crammed more pixels into the same space, and the > dimensions should be the same, right? > > > Shel >
