Image Resolution for Print II

A good place to begin is with a photo that may appear to be low res, but isn't really that bad because it is of a very large nominal size. I have no idea why a camera would be programmed to write a file that way, but let's take a close look at it (within the limitations of
the blogger environment).

To begin with I am using Adobe CS, as opposed to CS2 or CS3. That is Photoshop v8.0. I do not think that it will make much (or any) difference in what we will cover here though.

We will begin working with an image that I shot from my front porch recently. After I open it in Photoshop, I choose Image>Image Size (nothing surprising there).

The resolution is listed at 72 dpi, but look at the Width! 41.778 inches. That is a large photo size. But all that has happened here is that the relationship between the nominal Document Size and the Resolution has been inverted. If you change them back around you will see the true size of the file at 300 dpi.

First it is very important to notice that Resample Image is checked (at the bottom). You can also see this because only the Width and Height are "linked." This keeps the Width and Height linked together in proportion to one another if you make some sort of a change, but Resolution is currently excluded. So if I change the Resolution from 72 to 300 now, I will get a file that is 41.778 x 27.778 at 300 dpi, and Photoshop will have to process the file to calculate this out. Since that cannot actually add real image resolution to the photo and will create a document is 426% larger in file size, that is not the way to go.

So I uncheck Resample Image (which now links Width, Height, and Resolution) and change my Resolution to 300. The Document Size becomes a much more reasonable 10.027 x 6.667 inches. This is the actual size of the file at 300 dpi. So all's well as ends well and you should have no problem with most reasonable uses of this file.

The troublesome part is if your original size is 10.027 x 6.667 inches and your Resolution is 72 dpi. If you convert that to 300 dpi, you will see that you only have a 2.407 x 1.6 inch image to work with. That might be ok if it's going to be used at a very small size anyway, but most of the time that simply would not do.

You might need to play with these settings to understand what is going on here, but you should understand the gist of it.




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