Does anyone know how to crop an image with a preset aspect ratio without resizing the image?
I've been a Paint Shop Pro user for years, but everyone else in my workplace uses Photoshop, so I'm trying to transfer my skill set.
Compared to PSP, I find that Photoshop puts way too much emphasis on Dots-Per-Inch (DPI). Normally, when I'm working on a photograph, I want to manipulate and crop the photo while retaining the maximum number of pixels (the mega-pixel count). I haven't figured out how to do this in Photoshop.
For example, in PS 7, if I want to crop a photo to fit a 7" x 5" frame, I
- Select the crop tool
- Manually type width="7.0 in", height="5.0 in". This will force the selection tool to conform to a 7-to-5 aspect ratio while I resize and drag it around the screen. So far, so good.
- Now the crop tool requires that I select a DPI setting so that it can resize the image, which is ridiculous. People in forums often say things like, "Set this to 300 DPI for print or 72 DPI for web", but these are flaky artists who don't understand math. What I really want to do is to crop the photo to a specific aspect ratio while retaining the maximum possible resolution; the software should automatically calculate the new DPI setting, rather than having me guess it (or using a calculator to manually calculate the new DPI, as I've been doing).
Some have suggested that, to retain maximum quality, I should just set the DPI to a really large number like 1,200. But this actually results in an overscan resize, which does nothing to improve quality and results in a larger than necessary file size.
As an aside, the suggestion that there is a fixed DPI of 72 for web/screen is a fallacy. For example, I'm currently writing this on a laptop with a screen that is 9" high, with a resolution of 1280x1024. Suppose I display an image that is 640x480 pixels on the screen. Therefore, the height of the image is:
(480/1024) * 9"= 4.22" high
with a Dots-Per-Inch of:
480 dots / 4.22" = 114 DPI
Now, suppose that I plug my laptop into an old LCD projector which has a resolution of only 640x480, and it projects the image onto a screen that is 10 feet high (120"). The new DPI is:
480 dots / 120" = 4 DPI
So the exact same image will have a different DPI depending upon the resolution and the size of the monitor it is viewed on! This is why, in the web world, we couldn't care less about the theoretical DPI of an image. What we always want to know is the PIXEL RESOLUTION of the image (ie: 640x480), or the number of mega-pixels. This tells me everything I need to know. |
