Dpi

[darktiger]

What will happen if I change my pic that is 72dpi to 300dpi. Or is it already too late? Is there any benefit, or is all the info already lost.

[brad]

Sigh. This topic comes up regularly, and you will get a number of comments, some accurate, some not.

DPI is meaningless when it comes to the file itself. A 6MP file is a 6MP file is a 6MP file. It is what it is.. on a Canon 10D (the device with which I am most familiar), it is a 3072 x 2048 file.

DPI only matters when you go to display the image. Monitors are traditionally 72dpi, although this isn't so much true anymore with higher density displays of the last few years. 300dpi is traditional printing, but it gets really confusing when you see that printers have resolutions in the 1440dpi and more range...

The simple answer: don't worry about DPI until you are trying to print it. When you do that, a general rule of thumb is that the lower the dpi, the less quality you are going to see. If you took a 1000x800 pixel image and printed it as 8x10, there is only 100 pixels of information per inch.. which isn't going to give you a high quality image..

Now, there are in depth, detailed explanations out there that will only serve to confuse you (and sometimes the poster), but that is the simple version.

As for sizing an image's pixels upward.. say from 3000x2000 to 6000x4000 .. if you think about it, you should realize that this is not something that will work. You have 6 million pixels and you are turning it into 24 million pixels... four times as many.. where do you think those pixels come from? A pixel is one color only.. those extra pixels are "made up" by the software... you might get tolerable results, but only with a lot of fiddling with settings... and you are never going to "get back" data that was never there to begin with.

[darktiger]

I am trying to make it print quality. I have some pics at 72dpi shot with a Fuji S3 and would like to print them with the best quality possible.

[brad]

The resize tool has a place where you can change DPI, but if you watch, when you change the DPI in that tool, the pixel dimensions of your image change also... not usually a good thing.

Resize the way you were thinking.. then zoom into the image at 100% and see what it looks like.

The other way is to take your unmodified file down to one of these places that you can just stick your digital card in and get a print... print the unmodified/unresized original at 8x10 and then print the one you changed the dpi on at 8x10 and compare the two... I'll bet you that the two images are either identical, or the one you resized will be slightly worse.

[ShutteredEye]

Rather than worrying about the image being at 72 dpi, what I do is look at the total pixel size of the image and divide by 300. This gives the largest print you can make at "photographic quality." For example if my image is 2400x3000, dividing by 300 yeilds 8x10. However if the original image size is 1200x1800 instead, dividing by 300 yeilds 4x6" print. Some say that you can get away with less than 300dpi and still be photographic quality. And there are also programs out there that will add pixels to your image, interpolation(?) that allows for prints at much larger sizes.

[exposedmedia]

Originally Posted by brad

As for sizing an image's pixels upward.. say from 3000x2000 to 6000x4000 .. if you think about it, you should realize that this is not something that will work. You have 6 million pixels and you are turning it into 24 million pixels... four times as many.. where do you think those pixels come from? A pixel is one color only.. those extra pixels are "made up" by the software... you might get tolerable results, but only with a lot of fiddling with settings... and you are never going to "get back" data that was never there to begin with.

You are almost quoting my instructor word for word there.

[rwwright]

many people cannot tell the difference between "photographic quality" and an image printed after enlarging it somewhat. The secret is how much you enlarge it (ie how many pixels the program must make up for you). I regularly print my d2x images at 13x17 and often must crop a bunch of the photo.

I printed a very satisfactory image from a 6 megapixel camera that was printed at 24x30. Close inspection would reveal that it would have had cleaners details if it had been taken with a 8x10 view camera. But it was just fine for 95% of the viewers. Just dont take a magnification glass to it.

Some people say that you should always print at 360 dpi with the last few years of ink jet printers.

I find that cs2 is really good at enlarging an image but still use genuine fractals occasionally for enlargments.