JPGs - not for printing!

JPEGs (or .jpg) - everyone uses them, no one understands them. The name comes from the Joint Photographic Experts Group which came up with the standard for compression of photos. The compression methods is usually lossy compression (as opposed to lossless compression) which causes degradation of the photo. I know, every camera shoots jpgs and they look fine, but the lossy compression method is progressive and once gone can't be returned to its original state.

Good advice came from Suzanne Salvo, "when you download your photos from your camera, burn a cd of the files (never write on the cd with a sharpie) and file it away, take the photos on your computer and convert to psd files immediately".

I want to return to the statement that the method is progressive, what that really means is if you keep the file as a jpeg each time you open and save the file it recompresses it, causing more loss of data. So it may look fine when you start but can completely degrade over time. To the point it is no longer usable.

Print dpi - dots per inch. In the old days before quick printing, the measurement was in lpi or lines per inch and early versions of Photoshop allow you to set the lpi and the dpi was set for you. Now we all use the dpi, the question is what is enough? The trick is to balance a good output photo with a file that is easily managed. I used to have an equation that allowed you to take the output of the printer, ie 600 dpi and calculate the maximum dpi needed for your photo, but after all the calculations if you just divide by 2 you'll come really close. So if your output is at 600 dpi, the most you need is 300 dpi on your Photoshop image (at size of course).

I use a Xerox Docucolor 6060 color printer and it has beautiful output. I took a photo at 8 X 10 and set it at 200 dpi and printed - looked great, I then rescanned and printed it at 300 dpi, looked great. In fact it was hard to tell the difference without a loupe. The difference? The 200 dpi was 20 megs the 300 dpi was 45 megs - over twice the size with no gain in output. I think 200 dpi will work for most applications. BTW I also did the same on our HP 5500 inkjet poster printer, pretty much the same story - except you can take the dip down to 150 dpi with little change in the actual output.

My recommendation? Check with your local printer - see what they require and don't use jepgs!

This is scary

http://news.bbc.co.uk/2/hi/technology/6929258.stm

With continued and expanded use of the internet for everything in our daily lives, security will be the next big thing.

ch