RAW to TIFF DPI 20D

[Doom1701e]

This is probably a better question for the post-processing forum but since there are so many 20D freaks in here I thought I would post here. When using the 20D viewer utility and exporting a RAW to 8bit TIFF, what DPI setting is the best. When I converted my first the default came up at 96, but I uped it to 180 since that is what the 10D seemed to put out. Is 180 ok or should I go to 96? Or is there a better setting I should use? Thanks!

[Jesper]

It doesn't matter. The DPI number doesn't mean anything. The only thing that's important is the size of the image in pixels. Only when you're going to print your image, you'll want to print it at a certain real-world size and the DPI number becomes important.

Look at this article: Display, Printing, DPI and PPI (http://www.photo.net/learn/resize/)

[Jim_T]

Yes.. Until you put the image on paper, DPI is meaningless..

DPI is a printing term. It's *nothing* more thant the number pixels in an image divided by the number of inches of paper you plan to spread them across. When you attach a DPI value to a file, you've attached a default printing size and nothing more.

A 300 pixel wide image spread across one inch of paper has 300 DPI. It CAN'T be anything else. So setting a 300 pixel image to print 1 inch wide is EXACTLY the same as setting the DPI to 300. There's no difference.

If you look at the "image size" window in whatever software you are using, you'll see there are also inches shown. (There have to be inches otherwise you couldn't have dots per inch). The DPI is *always* equal to the number of pixels divided by the inches. When the software shows you the DPI, all it is doing is dividing what's in the pixel box by what's in the inches box. The inches the software is showing you are always inches of PAPER.

If you have Photoshop, you'll see in the image size window, that they are careful to break it into two sections with a thin line.. The top is labled PIXEL DIMENSIONS.. This only shows pixels. This is all there is in the file. The bottom section is labled the DOCUMENT section.. This shows inches and pixels per inch.

The Pixel Dimensions show you the width and height in pixels. That is all you can change there. The DOCUMENT is what the image will be like when it is printed on paper... Here you can change the print size in inches.. And of course when you change the print size, the program divides the number of pixels in the image by the print size you chose and tells you how many dots per inch you will have when you print it. at that size.

Changing the DPI of an image does nothing to the pixels in an image. All you are setting is a couple of bytes in the image header. These bytes are meant to be read by your printing software. The value of these bytes tell your printer how big to make the image.

The DPI can be anything you want.. As Jesper says.. Unless you're actually printing your image, DPI is meaningless