Following some of the points raised about resizing images I put together this comparison which may be of some use. Download, and use the zoom control to examine the details in the 5 images:
Image 1. Original, unsharpened, width 1400 @ 72dpi Download all the images Here
Image 2. Sharpened, width 1400 @ 72dpi
Image 3. Sharpened, width 1400 @ 300dpi
Image 4. Sharpened, width 1024 @ 72dpi
Image 5. Sharpened, first resized to width 1024 then to 1400 @ 72dpi
Sharpening was done to the original image before any resizing. No other manipulation has been done.
It is interesting to compare Image 2 and 3: 300dpi is usually only needed if the projected image is to be printed, in an exhibition catalogue for example, and also note the loss of detail due to “up-sizing” Image 5, (always manipulate a copy of the original full size image, and go back to this one to resize)
The following is from Corel Paint Shop Pro Photo help, but also applies to Photoshop (By the way - does anyone use any of the resizing methods other than “Smart” resize mentioned below?):
Here are some recommendations to help you resize your images:
Avoid increasing the image size by more than 125%. Doing so may cause a loss of detail and sharpness.
Resize an image only once. If you resize the image incorrectly, undo it and try again.
Correct and retouch images before resizing.
Choosing a resampling type lets you choose how the image is resampled. In most cases, it is best to use Smart Size, the default setting.
The resampling types available in Corel Paint Shop Pro Photo are described in the following table.
Chooses the best algorithm based on the new pixel dimensions you set
Minimizes the jaggedness that often results from expanded, irregular, or complex images
Uses the two nearest pixels around each existing pixel to determine the appearance of newly created pixels
Duplicates or removes pixels to achieve the selected width and height of the image (recommended for hard-edged images and simple graphics)
Uses a weighted-average color value of neighboring pixels to determine the appearance of newly created pixels (useful for reducing photorealistic, irregular, or complex images)
Hope some of this may be of interest.
Also see this resizing guide using Photoshop- down load the file here