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Old Feb 8, 2005, 9:42 AM   #1
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I have downloaded one of my pictures from CD as....

1024x1536 pixel (4.5m) with a document size of 10.16 x 15.24cm with a resolution of 256 pixel/inch with the resample image not ticked.

Say, when I get much better at takingphotographs :lol:I want to submit them to a publisher :lol::lol:and they request a 300dpi with a 8x6 min size...would the above be acceptable (I haven't got my head round dpi even after reading all the other posts...sorry) or would I need to alter it and how, for acceptable publication....sorry to sound so dopey but I need to ask...
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Old Feb 8, 2005, 10:23 AM   #2
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The DPI will depend what you're getting published in, in UK 85 - 110 is enough for newspapers... around 180 for magazines.. 330 is only really for the poshest glossy books. (but the printers are scared incase they print something fuzzy - and get blamed!)

I reckon the resolution you mention should be ok, if in doubt give them the best you have on a CD, I would say around 10mb for letter size
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Old Feb 10, 2005, 4:50 AM   #3
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Pixel dimensions are fixed and this is what you shot in your camera. For example a 6 Megapixel camera will shoot something like 3000x2000 pixels. You can change this up or down by interpolation but this is the native resolution of the shot.

Pixels per inch or PPI is how you spread these pixels out to display or print the picture. so if you wanted to print the 6meg picture at 6x4 then the PPI would be 3000/6 = 500 PPI or 2000/4 = 500 PPI. I chose 6x4 deliberately becausethe ratio ofheight to width matchesthe original. In the example you give 1536 x 1024 is not the same aspect ratio as 8x6. to get the correct aspect you would have to crop to 1365 X 1024 andthat would give a PPI of 170. or uncropped you get 9x6 at 170PPI. If you know your target is 300 PPI you could try interpolating to up the resolution.

DPI actually refers to the printing process and is a completely different subject. An ink jet printer, for example,may have a resolution of 1400 DPI and this refers to how it can lay down the ink on the paper. Every pixel in your file will be converted into a collection of dots of black, yellow, magenta and cyan inks on the paper. The DPI of the printer relates to how well it can convert your pixels into a smooth, true colour print.
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Old Feb 11, 2005, 9:45 AM   #4
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There's a whole article on pixels PPI and DPI in tech corner http://www.steves-digicams.com/techc...uary_2005.html
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Old Feb 26, 2005, 3:39 PM   #5
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You can up the dpi with out a resample. As poited out by Nagasaki there are no more pixels in the image to play with but in photoshop if you turn of resample in the edit image size dialog box, it offers you only the physical size to alter. The screen size will remain the same but you will reduce or increase the print size by changing the pixels/inch on your image if you change this to 300 p/i then you wil lhave a physical print size maximum (with out loss) of 8.67cm x 13cm.
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Old May 13, 2005, 5:50 PM   #6
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dpi is different fromm ppi

ppi are pixels per inch, the number of pixels in an image.

dpi are dots per inch. This is what inkjet printers are generally rated in. Each dot is not a pixel, but a single color that would make up the pixel. 1200dpi is approximently equal to 300dpi. So if they request 300dpi, they only require 72 or so ppi, if they are on the standard.
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Old May 15, 2005, 10:59 PM   #7
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Carskick wrote:
Quote:
1200dpi is approximently equal to 300dpi.

I hate that new math. :roll:
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Old May 16, 2005, 4:13 PM   #8
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Carskick wrote:
Quote:
dpi is different fromm ppi

ppi are pixels per inch, the number of pixels in an image.

dpi are dots per inch. This is what inkjet printers are generally rated in. Each dot is not a pixel, but a single color that would make up the pixel. 1200dpi is approximently equal to 300dpi. So if they request 300dpi, they only require 72 or so ppi, if they are on the standard.

DPI and PPI aren't quite so easily defined. Inkjets have muddied the water and most people use PPI to keep them separate, but it is still not totally improper to use DPI for pixels and some printing houses still do.

As far as the relationship to inkjet, PPI varies with the printer. 8-10 picolotre printers used 16 dots per pixel. 4 and 5 picolitre dot printers used 32 dots. I've read but not confirmed that 2 picolitre dot printers use 64 dots per pixel and by deduction it seems the 1 picolitre printers use 128.

The old printing rule was that you need 1.5X the LPI for good quality and some processes could require up to 2X. This is based on LPI, but the maximum DPI on an inkjet is in the vertical and equates to lines. So 300 PPI equaling 1200 DPI would relate only to an old pre-8 to 10 picolitre dot printer or a process other than inkjet.

Printers don't use all of the available dots unless they are mixing colors to give pure black. But the resolution is based on using them all. The resolutions have gone up pretty much in relation to the dot size so that the newer inkjets require about the same PPI input as the older ones. I don't think there is an inkjet on the market that can really use over 300 PPI even though resolutions are near 6,000 DPI.

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