Hints - Understanding Image Types

Image File Format definitions 

There are two image main image file format definitions used in a typical graphic design project. Raster (or bitmap) images and vector images.

Raster images

Raster images are generally photographs or images made up of pixels. These images are resolution-dependent, meaning that their physical size is directly associated with their resolution (the number of Dots (pixels) per Square Inch or DPI that they contain).

Raster images are the most common electronic medium for continuous-tone images, such as photographs or images created in painting programs, because they can represent subtle gradations of shades and colour. Bitmap images are resolution-dependent. This means that they represent a fixed number of pixels. As a result, they can appear jagged and lose detail if they are scaled on-screen or if they are printed at a higher resolution than they were created for.

Vector graphics 

Drawing programs such as Adobe Illustrator create vector graphics, made of lines and curves defined by mathematical objects called vectors. Vectors describe graphics according to their geometric characteristics. For example, a windmill drawn as a vector graphic is made up of a mathematical definition of shapes drawn with a certain height and width, set at a specific location, and filled with a specific colour. You can move, resize, or change the colour of the windmill without losing the quality of the graphic.

A vector graphic is resolution-independent - that is, it can be scaled to any size and printed on any output device at any resolution without losing its detail or clarity. As a result, vector graphics are the best choice for type (especially small type) and bold graphics that must retain crisp lines when scaled to various sizes - for example, logos.

File format differences

Images: RAW, Tiff, BMP, and PNG are all lossless image formats

Images: JPEG and GIF are lossy image formats

If you want to put a photo on the web, you should use a lossy format to reduce that photo’s size. (but keep a backup of the original lossless file)

If you’re printing the photo professionally, you’ll probably want to use a lossless format during the editing process. (Note that, for screenshots, PNG is a lossless format that can create appropriately-sized, sharp screenshots out of the flat colors found on computer screens. 

However, PNG becomes much larger if it’s used for photos, which contain much more jumbled up colors from the real world.)

Raw Files (non-destructive edits)

Raw image files give your photos so much more. 

Raw files contain unprocessed data from your camera and are sometimes referred to as digital negatives. Since you have all the original data to work with, you can make bigger corrections when you process your photos.

Adobe Camera Raw can open most raw image formats from professional and midrange digital cameras. Using the Camera Raw editing tools, you can fix color problems and uncover more details hidden in shadows and blown-out highlights.

Adobe Camera Raw lets you correct many image perspective and lens flaws by synching the raw file with your specific camera and lens profile. It also offers additional ways to correct lens distortion

Use Adobe Camera Raw as a filter to make non-destructive edits to all your images and layers.

The way it was described to me is the raw system creates a recipe card that you apply to the image. you can create many recipe cards and switch between them leaving all the original data intact this only possible because the raw data is intact when you set your camera to jpeg it processes at the camera level discarding information, yes the file are smaller but you can’t get back what you never had.

Tip check to see if your camera shoots in Raw I have two separate cards one records JPEG the other to Raw just remember your raw SD card needs to be at least three times as big as the jpeg to capture the same amount of images

JPG: (destructive edits)

The JPG file format, short for Joint Photographic Experts Group, is a type of image compression that works best with photographs and complex images. JPGs use a compression method that removes non-human-visible colors from images to decrease file sizes. Be careful, though. If you decrease the quality of a JPG too much, you will begin to lose important color information that cannot be recovered.

The JPG file format also allows you to save progressive JPGs, which will load in stages. You may have experienced this before when visiting a website and watching as an image slowly loses its blurriness and becomes clearer.

Use JPGs for product photos, human portraits and other images where color variances are important. Do not use JPGs if you need transparency, which is the ability to see through an image and decipher the background behind it. JPGs do not support transparency.

PNG:

PNGs, or Portable Network Graphics, were created as an alternative to the GIF file format, when the GIF technology was copyrighted and required permission to use. PNGs allow for 5 to 25 percent greater compression than GIFs, and with a wider range of colors. Like GIFs, PNG file formats also support transparency, but PNGs support variable transparency, where users can control the degree to which an image is transparent. 

PNGs also support image interlacing, similar to GIFs, but PNGs use two-dimensional interlacing, which makes them load twice as fast as GIF images.

GIF

A GIF, or a Graphics Interchange Format, reduces the number of colors in an image to 256, from potentially thousands of colors coming from a digital camera. GIFs also support transparency.

GIFs have the unique ability to display a sequence of images, similar to videos, called an animated GIF, which is a series of separate GIF images that are linked together to automatically create motion, or animation. Although the GIF format is still in use, it should generally be avoided in favor of the PNG format, which does nearly everything better.