File Format

File Format

When an image is captured by a camera or a scanning device it has to be saved or memorized in a 'file format'. The information can only be read and understood if the software recognizes the format.

The dominate formats are:

•   JPEG (joint photographic experts group) JPG.

•   TIFF (Tagged Image Filme Format) TIF.

•   PSD (PhotoShop Document) PSD

•   RAW (Raw Unprocessed Information)

File > Save as - This opens up numerous options for the photoshop / P.C. user for simplicity it is advisable that you save your work as either a TIFF or PSD file because they support all of photoshops features. Note:  not all formats support layers.

Tiff this format is generally regarded as the industry standard because it is the most universally recognized format. Photoshop's variant of this format supports image layers,adjustments, layers, paths, clipping paths and ICC profiles. It's the most  popular format for photographers delivering RGB and CYMK files to clients. It's good practice to flatten files because only photoshop supports layered tiffs.

PSD

Photoshops native format supports everything photoshop can do including ICC profiles. Until version 6 it was the only format that supported layers. This format is only recognized by photoshop so it is not advisable to hand PSD files over to clients.

JPEG

The most commonly used file format. It as 'lossy' compression that transmits what it seems to be important content and discards colour information that it considers redundant. There is no option to save without compression but embedding ICC profile is an option. JPEG allows you to make a trade off between image file size and image quality. JPEG compression divides the images in squares in 8x8 pixels which are compressed independently. As you increase compression the squares become more visible.

100% quality JPEG. IS very hard to distinguish from the uncompressed original typically taken upto 6 times as much storage space.

80% quality JPEG still look good although it is 10 times smaller than the uncompressed original. Some detrition will occur however.

60% quality JPEG 20 times smaller than the uncompressed original sufficient for website use.

10% quality JPEG this will show serious image declaration with very visible 8x8 JPEG squares. It is unlikely that you will ever use this level of compression but it illustrates what JPEG os doing at higher quality levels.

Upon close inspection of a compressed JPEG blocks of 8x8 pixels can become evident because of this degrading it is advisable to avoid saving in this format for high quality images.

JPEG can use several layers of compression dramatically reducing the size of closed files compared to their open state. If an image is shot on JPEG avoid re-saving as a JPEG as it will further degrade the image; save as TIFF.