changing DPI

Ok try again with your example
Pixel Dimensions:
Width: 2048 pixels
Heigth: 3072 Pixels

Thats all that matters - thats the quality on screen and stored.
Now you want to print the image
SO as a rule of thumb you will need to have 300 pixels for every inch of paper
so you have 3072 pixles and have to divid that by 300 to see how many inchs you can print
3072/300 = 10.24"
2048/300 = 6.8"

so thats the biggest print you will get at high quality printing.
NOW some people say you dont need as much as 300 PPI to get a good quality print and these varies from person to person - some epson printers will provide a good quality print at 240PPI so with less of YOUR pixles per inch you can get away printing larger

can you print 20x16
so you have 3072 and want a size of 20"
Pixels / PPI = inches
so Pixels/iches = PPI
3072/20 = 153PPI
can you get a good quality print with only 153 pixels for each inch - i dont think so - but other may disagree and lots of threads here - final test print it out and see

i'll wait for your response before answering the question re 10D raw and setting - if you still dont understand as we are crossing

Ok . I understand that now. Thank you for making it easier for me to get. You are very patient. Now...shooting in raw...does that just mean I can set things however I want? And the pixels to whatever I want? Should I just shoot in raw and it will fix the problem?

Jolne, what you need to know is fairly simple. Break the process down into steps....

First - what are the horizontal and vertical pixel count numbers of your image? For your camera, those numbers are 3072 and 2048 pixels.

Second - how large do you want to print? Let's use your example of 16x20 inches. First, the 16x20 format is not the same aspect ratio (width-to-height or height-to-width, how ever you want to consider it) as the camera's image. The camera's image has a 2:3 height-to-width ratio (assuming the height is the short distance, like your computer monitor). Thus, you will have to crop at least the long distance (width if in landscape mode like the computer monitor). Let's assume that works for you. The pixel count of the resulting photo image would be approximately 2560x2048 pixels.

Third - take the larger pixel count number (the 2560) and divide it by the inches across the long dimension of the print (20 inches). You will have 128 pixels per inch making up your print. Do the same math for the other dimension (2048 pixels vs 16 inches), and you get exactly the same pixels-per-inch value.

Fourth - you have to determine if the resolution of the resulting print will be acceptable to you. 128 pixels per inch is a little coarse for a lot of folks who might examine the print up close. Viewed from a couple of feet away, it might be quite acceptable. I think you will find that most printing is done at a minimum of 240 PPI, and some folks (like me) usually print at least at 300 PPI for maximum resolution of the print.

The actual "setting" of the PPI count is a process done when you tell your photo software what size to print to. This is the ONLY time that PPI means a thing to you. I hope the four-step thinking process above makes this thing with PPI count a little more understandable.

There is software available that will let you increase the image's pixel count so that you can make larger high-resolution prints. It isn't cheap, however. The latest version of Genuine Fractals - designed to run with Photoshop CS2 - has to run on an XP platform (for the PC) and costs about $200. You should also have LOTS of RAM memory in the computer to use that sort of software, adding to the costs.

This is nothing more than a math problem, folks ....

You already know just how many pixels you've got in your image file (above). And you're trying to find out how many pixels per inch will be in a 16x20 image from that image size.

2048 divided by 16 = 128 pixels per inch
3072 divided by 20 = 153 pixels per inch

So, if you set the DPI setting to 153, you'll get an image that prints at 20x13.25 (approximately). Most labs that I deal with insist that the image be 300 pixels per inch to print the best quality print.

Now, if you need to "enlarge" that print to 300 DPI AND print at 16x20, you'll have to "interpolate" that image "up" to handle the 300 DPI so that your image is 4800 pixels by 6000 pixels (300x16 and 300x20). You can do that in PS or you can invest in Genuine Fractals or you can just have the printer driver do that for you in the print process.

It's all in the math - multiplication and division .....

No ....

As I said, you're dealing with a math problem, not a shooting problem ....

RAW will enable you to change a lot of variables in your image, but it won't create pixels for you ....

ETAF and I were typing at the same time, it seems.....

RAW mode has no settings for the PPI value. Again, it makes absolutely no difference what number is chosen by Canon for the camera's image data. It's only when printing that you would even care about the PPI value, and it's when you spread the pixels in the image file across paper that it is determined.

RAW images allow you to have MUCH more control over the image than shooting in JPG mode, for example. When converting RAW images to other file types (which must be done - you don't work directly in RAW), you can choose the color balance that you need - you may have chosen the wrong color balance setting in the camera, for example. You can also make other changes when converting from RAW, but for most people the main advantage is the simple color balance conversion.

RAW is like a negative it has not been touched by the camera software and will be how the sensor saw the image so you will get maximum size pixels and then you can make adjustments to the image like sharpening and colourspace - which the camera may set for you otherwise.
so you get more choice to change the image after the shot.
some people always shoot in RAW myself included and others prefer to shot in jpg - theres a lot of post on raw and jpg so have a search for RAW

skipD and again

Well I will work on it. Thanks for your help everyone. I just am worried that the photos I have taken, that need to get blown up, will look like crap.

No they won't. I have printed many 16x20 canvases from my 10D and they are beautiful. I resample to 200 dpi before sending the TIFF to the printer because the nature of canvas prints makes them a bit more forgiving of resolution so 200 is just fine. Actually even for traditional prints at that size 200 dpi would probably be fine unless you got right up next to the picture and then you would see a bit of fuzziness. But keep in mind the larger the print, the farther away it is intended to be viewed from. You can easily do 20x24 with a 20D and it will look great.

yep maybe, but thats because of the max pixels you have and thats why people spend extra money and instead of getting a 2MB camera get a 6MB camera because it has more pixels and prints larger as a result of more pixels.
but if you have used the maximum pixels available from your camera than that the biggest print you will get - now getting to 20x16" may need some manipulation in photoshop or GF - but until you print it you wont know if its acceptable to you.

what size printer A4/A3 and make model do you have

SEE
twalker294
as I said different people have different views on what is acceptable and possible with PPI thats why its so difficult - I know someone who prints 20" off a 4MB camera - I think the prints look blotchy He loves them ......
give it a go.

hence printer question

Jolne, Have you ever had (or seen) film developed and prints made? You may well have asked for "4x6" - putting that label on doesn't mean it can only be printed at 4x6. It doesn't do anything to the negatives. It's just an instruction to the printer. You can take the same negatives later and say "16x24 please". Still the negatives don't change. If you want 16x20, you'll have to tell the printer which part of the negative not to print...

Same way, putting a "label" (or "tag") on the file in software saying "72ppi" or "300ppi" doesn't change anything about the pixels in the file, it's just an instruction that some printers need and you can change that at any time.
What you change it to will depend on how big you want to print. Then it becomes an arithmetic problem and a choice of how far away you want them to be viewed. If you print them too big, and look at them too closely, of course they'll look like cr*p. Same was true of film

Andy