Cropping a picture does three things to improve the digital image:
COMPOSES - It cuts away distracting or unnecessary elements in the image to help you "tell the story" as clearly as possible
SHAPES- It lets you choose a specific shape or "ASPECT RATIO" - ie
Square: 300x300 etc.
Standard Def: 320x240, 640x480, 800x600, 1024x768 - [This is 4:3 Ratio]
Widescreen: 1280×720, 1600×900, 1920×1080 - [This is 16:9 Ratio]
RESIZES - It typically reduces the digital file size, making the project more efficient
Here's an example of a yearbook photo improved by cropping
1. The original photo had good content, but included a large amount of "noisy" background elements, and "wasted" pixels around the actual subject.
2. A crop was chosen that matched the square frame we required for the layout. This also allows us to
"remove" the ugly powerlines in the background
Steer the focus so that the player dominates the frame
Compose the shot to draw attention to the action
3. The cropped photo is better composed, and "tightens in" on the subject. The subject's object of focus also becomes more obvious!
The options at the top of the screen will allow you to customize the HEIGHT, WIDTH and RESOLUTION.
Truthfully, the RESOLUTION setting can be left alone for webpage graphics - it only affects the size of your graphics when PRINTED by a professional service bureau.
You must type PX after your dimensions if you haven't set your preferences properly in Photoshop. The default is to measure in INCHES.
Widescreen aspect ratio:
800x450px (web page sized)
1280x720px (720p) @72pdi
1920x1080px (1080p) @72dpi
Poster Sizes
3400x2200px @200dpi (11x17" Poster)
1500x2100px @300dpi (5x7" Photo)
A 12MP camera is TOO GOOD FOR YOU!
It generates enough pixels to fill a 55 x 41 inch computer monitor at 90dpi... and they don't really make those yet
You typically need to REDUCE the number of pixels in a digital photo for screen display. You can do that by RESIZING your digital images. A decent sized graphic for a website will be about 800px x 600px
There are SEVERAL ways to resize a graphic, not including the CROPPING TOOL
IMAGE - RESIZE - IMAGE SIZE
Resample ON - You can reduce (or increase) the NUMBER of pixels. This is ideal for WEB DESIGN - where the output resolution is meaningless. Graphics can be sized to precisely fit the screen output (72 DPI)
Resample OFF - You won't change the total number of pixels in the image. You can ONLY change the "Output Resolution" for PRINTING purposes. The PIXEL DIMENSIONS and filesize will stay the same
Canvas Size - This can let you add or remove pixels from the outside border of the image, based on the ANCHOR POINT that you select. It's a little like using the CROP tool, but with numerical precision
Transform - Using CTRL-T you can resize a selected element on the screen, while leaving the canvas at the existing size.