Photoshop view sizes.

This may be a really dumb question but here goes.

If i have an image in PS and size it to 6x4 Inches in Image-resize why does it not dispay at 6x4 on the screen at 100 % ??

What i mean to say is that if i took a ruler to my screen and measured the displayed image at 100 % it would not measure 6x4 inches.

The physical size of the image (in inches) on screen depends on the physical size of the pixels on your display, and really doesn't relate to the defined print size (in your example 6x4 inches) of the image.

100% zoom in PS simply means that, each pixel of your image occupies a single pixel of space on your monitor.

For example, A 300dpi resolution 4x6 image has FAR more pixels than a 72dpi 4x6 image. When displayed at 100%, the 300dpi image will be HUGE on screen compared to the 72dpi image ... even though they are both cropped to PRINT at a 4x6 size.

Because 100% means that one pixel in your image corresponds to one pixel on your screen. If your monitor resolution is, say, 768x1024 pixels, an image whose pixel dimensions are 768x1024 will exactly fill the screen. A 2000x3000 image will overflow it and a 200x300 image will occupy only part of the screen. An image that is "sized to 6x4 inches" may eventually print out at that size, but until it is printed it has no inches, feet or yards dimensions, only the number of pixels.