Also, if there are any file-type DON’Ts to be aware of.
Jpeg is a "lossy" format. Once an image is saved as a Jpeg, a great deal of data is irrevocably lost. The greater the compression the greater the loss. Files should only ever be saved in this format for their final destination, be it for the web or when being sent for printing.
Opening and resaving Jpegs is a big NO NO, as each time more and more data will be destroyed. TIFF and PSD are lossless formats and the best choice for editing.
A good workflow involves:
* backing up your original camera file (TIFF or RAW. Don’t shoot Jpegs)
* After any editing, save your "Master File" at its generic size as a TIFF or PSD.
* After resizing – for print or web – save a copy at the new size (TIFF or Jpeg)
* NEVER resize an image more than once. Always go back to the master file and create a new copy at the new size.
Hope some of this is of use.
Chris.
PS: I’ll let someone else advise on PGN and the other formats as I’ve no personal experience of them.
I’ll let someone else advise on PGN and the other formats as I’ve no personal experience of them.
🙂 obviousley, I think chris ment PNG, even though there is a PGN file. Picatinny Arsenal Electronic Formstore Form in TIFF Format
PNG supports a large set of technical features, including superior lossless compression from LZ77. Compression in PNG is called the ZIP method. PNG has additional unique features, like an Alpha channel for a variable transparency mask, any RGB or Grayscale pixel can be say 79% transparent and other pixels may individually have other transparency values.
Here are some representative file sizes for a 9.9 megabyte 1943×1702 24-bit RGB color image:
File type File size
TIFF 9.9 megs
TIFF LZW 8.4 megs
PNG 6.5 megs
JPG 1.0 megs (1.0 / 9.9) is 10% file size
BMP 9.9 megs
Steven,
To maintain ALL of Photoshop’s features ‘master files’ should be saved as .PSD
PSD’s will also be fine for placing in other Adobe applications, but not necessarilly applications from other vendors.
For professional print output TIFF is the most reliable/universal although .PDF is catching up and has advantages such as retaining vector content as vector.
Saving as JPG gives you a smaller file size at the expense of some loss of quality – the greater the saving on file size (the compression), the more quality will be affected. Additionally, each time a JPG is changed and re-saved, additional image degradation takes place. JPG is fine for local printing and Office use, and is also the de-facto standard for web images.
GIF is limited to 256 colours, but produces small file sizes. Use is generally restricted to the Web. It is very good for greyscale images destined for web viewing (since they only contain 256 shades of black anyway). It supports a SINGLE level of transparency – i.e. ONE single colour can be made transparent, but there is no translucency)
PNG-8 is a replacement for GIFs. PNG-24 supports the full 24-bit colour spectrum and translucency. Designed for web use, but unfortunately browser support for the format is very mixed – Internet explorer only supports them with the addition of an Active-X control. PNG can be useful for putting images into Office applications.
SCT is Scitex format – only used for hi-end colour separations.
EPS – Used to much more widely used than is now the case. Supports 1-bit transparency by use of clipping paths and can retain vector data as vector. Major drawback is that you need a PostScript printer (or PostScript interpreter) to output them.
PDF – Is set to become the universal method of data tranfer (not data exchange) between designer and printer and is much used in the publishing world. Supports various methods of compression, retains vector as vector, can embed fonts has security options, and can be viewd by anyone using the free Acrobat Reader.
That’s a VERY brief overview of just SOME of the graphics formats around.
I only ever work in and save my files as PSD.
If some one asks for a file for a presentation I supply it as a 150 ppi rgb jpeg (setting 8).
If its for some one to e-mail a graphic to show some one a product I supply a pdf set to 1000px 72ppi rgb jpeg (setting 8).
If its for a web site, I supply either a 72ppi rgb jpeg or giff depending on what gives me the smallest file size, or if there is any tranparancy.
And for a printing press, a PDF actual size, 300dpi, cmyk and text converted to curves with zip compression. If its a printer who I havnt worked with before I always save the PDF as version 4, this can stop problems with transparancy layers if the printer is uisng older software.
Thanks to you all for your feedback – it has helped a lot.
Cheers,
Steven
