Resolution and compression level
In addition to letting you choose a file format for your photos, most digital cameras enable you to choose the image resolution. Usually, you will choose the highest resolution — after all, that is what you paid for in the camera.
Image resolution is expressed in terms of pixels, such as 3648x2736 pixels. If you multiply these two numbers together, you get the total pixel count — for example, 3658x2736 = 10,053,888, or 10 megapixels (10MP). For most photography, 10MP easily gives excellent prints up to 13x18. More pixels in a picture are not about quality, but about image size. More pixels enable you to print at larger sizes, which could be one reason to buy a digital camera with a higher megapixel rating.
This is not a simple decision, however. More pixels on a small sensor can mean increased noise in the image (noise looks like grain in film or “snow” on a TV with poor reception). Also, as pixel counts increase, so does file size, meaning you need more memory to hold the same number of images, requiring you to purchase higher-capacity memory cards for extended shoots. You could gain space by choosing a smaller image resolution or a low JPEG compression. Unfortunately, both of these options reduce image quality. Choose the highest resolution and highest quality JPEG compression unless you have special need for small images, such as those used only on the Web (which needs a much lower resolution).
By reducing the image resolution to store more photos in your camera, you reduce your ability to crop photos later and the opportunity to get the largest possible prints. Memory card prices are very reasonable for high storage capacities, so buy either extra or big cards so that you can store your images at the maximum image resolution and with the least image compression. This helps you avoid taking a prized shot that is too small or has too much compression to make a good print.
Each time you save a JPEG file after editing it, your image degrades. Therefore, JPEG should not be used as a working file format when adjusting it in Photoshop Elements or any other program. Save a working file in an uncompressed image format such as TIFF (.tif) or Photoshop (.psd). JPEG can be used later for archiving finished files to save disk space.