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Old Aug 13, 2004, 12:49 AM   #1
obrien040362's Avatar
Join Date: Jun 2004
Posts: 38

When I open a picture with Microsoft Picture It Photo 7 It has a size of 8.53 x 11.38 with a resolution of 180 dpi.

Since this is not a 4:6 ratio and I want to print 4:6 borderless I do the following:

To get basically the whole picture i crop to 7.58 x 11.37 (4:6 ratio). Then I print on paper size 4:6. This would then print at something greater than 180 dpi?

To crop a portion Icrop a box in a 4:6 ratio (say 2:3 or 4:6 or 5:7.5). Then I print on paper size 4:6. A 2:3 crop printed on 4 x 6 paper would be less than 180 dpi ?

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Old Aug 13, 2004, 2:38 AM   #2
Lin Evans's Avatar
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Posts: 1,141

First, the issue is that the 180 dpi is simply a "tag" which is actually meaningless without being related to a print size.

Long ago, the MacIntosh displays were 72 pixels per inch and when PhotoShop was first designed most graphic artists used MacIntosh computers. Adobe decided to choose 72 pixels per inch (in display terms) to "tag" the images so that whenever the images were displayed the "default" print size would match the display resolution. Over the years this became virtually meaningless. As camera resolutions increased this meant that a 100 percent display size for something like an 11 megapixel image would be huge and would require the user to either downsample for viewing (PhotoShop does this automatically these days) or scroll around to see the entire image which wouldn't fit on the screen in its entirity.

Most digital camera manufactrers also chose 72 pixels per inch to "tag" the images to match the PhotoShop default. When the Canon D30 was introduced, Canon elected to tag at 180 ppi and confusion began to reign.

Typically, printers require somewhere between 300 and 720 dots per inch for optimal quality. Commercial printers such as dye sublimation use 300 dpi or 400 dpi and inkjet printers such as the Epson series have a print driver which interpolates to 720 dpi for highest quality print.

Think of it like this. If you have a 2 megapixel image it consists of 1600 horizontal pixels by 1200 vertical pixels. There is ony one single size which can be printed at a given print dimension without either adding or deleting pixels. Let's say you are printing on a dye sublimation printer which requires 300 pixels per inch input. Divide 1600 by 300 (actual number of pixels by pixel density required) and you get 5.33 inches. Divide 1200 by 300 and you get 4.00 inches. This means at a print density of 300 dots per inch you could only print at 5.33 by 4 inches. To get ANY other size you must either crop the image to a different aspect ratio, add pixels or delete pixels.

The "easiest" way for you to do what you want to do is to get an inexpensive piece of software which does it all for you. My suggestion is to do your photo manipulation (color, contrast, hue, etc.) with what you have and buy Qimage to do your crops and printing. Qimage will automatically "talk" to your printer, interpolate to give the ultimate in print quality and take care of all the "housekeeping" for you so you don't need to worry about the details. Here's a link where you can download a free trial version to experiment with:


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