Pictures Are Files-Files Are Formats

Pictures Are Files-Files Are Formats

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

The dominant formats are:

·      JPEG (Joint photographic experts group) .jpg

·      TIFF (Tagged image file 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 either TTIF or PSD file because they support all of Photoshop’s features. Note: Not all formats support layers.

TIFF-This format is generally regarded as the industry standard because it is the most universally recognised 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 CMYK files to clients. Its good practice to flatten files because only Photoshop supports layered tiffs.

PSD-Photoshop’s native format supports everything Photoshop can do including ICC profile. Until version 6 it was the only format that supported layers. This format is only recognised by Photoshop so it is not advertisable to hand PCD file over to clients. 

JPEG-The most commonly used file format. It has ‘lossy’ compression that transmits what it deems 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 optional.

JPEG allows you to make 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-Very hard to distinguish from the uncompressed original typically taking up to 6 times as much storage.

80% Quality JPEG-It 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 image degradation with very visible 8x8 jpeg square. It is unlikely that you will ever use this level of compression but it illustrates what JPEG is doing at higher quality levels.

Photoshop: PSD (Portable document format)- This format can support layer files can be re-opened and edited in Photoshop. A group of images can be saved as a multi page document. PDF supports various compression amongst them are ZIP, JPEG and JPEG 200.

Upon close inspection of compressed JEPG blocks of 8x8 pixels can become evident. Because of this degradation 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 resaving as a JPEG as it will further degrade the image; save as TIFF.