Tuesday, March 13, 2012

A Little Bit About Saving JPEG Files

I'm sharing another techno tidbit I wrote up for Dream Big Designs....Last week I talked about PNG files and saving them.  Today we'll be learning about JPEG files and saving options.  JPEG (pronounced jay-peg) is an acronym that stands for Joint Photographic Experts Groups and is a standard file format used for photographs.  It allows for compressed images that maintain maximum color and tone.  Because JPEG files get compressed every time you save them, you don't want to keep saving the JPEG file over and over again because it will degrade in quality with each save.  So with our precious photos, you never want to edit and save over your original image.  If you want to edit your photos, keep the original intact and save any edited versions as a copy, just in case you need to go back to the untouched original.

In our digital scrapping world, we use JPEG files for saving our layouts that we can later display on the web in a gallery or blog, or print them into a photo book.  And of course, there's lots of options and choices you have to made when you save your documents.  So let's see if we can figure that out and make it simple to remember.

With my layouts, I end up having 3 saved versions.  First is the layered PSD file.  I keep these in case I need to make edits, fix typos, or turn the layout into a quick page or template.  Next is a saved JPEG version at 72dpi that's been resized to 600x600 for displaying in galleries and on my blog.  And finally there's the 12x12 JPEG file at 300dpi for printing.  Doing this hogs a lot of space on your hard drive so you want to make sure you've got the right balance between file size and image quality. 

Starting with our PSD file, we need to flatten the image.  Flattening an image takes ALL the active layers (hidden layers are ignored) and consolidates them into 1 image layer.  This immediately reduces the file size.  Merging allows you to select a group of layers and combine them into 1 image.  Flattening works on ALL the layers, merging gives you flexibility to select just a few layers to combine.

When we are saving our layouts for printing, the biggest concern is getting the best quality image we can.  Since we've spent hours and hours working on creating a beautiful page, you don't want to sacrifice any quality when you save it as a JPEG.  When you select SAVE AS JPEG, you need to make a decision about image quality and format.  The Image Options allow you to balance between larger files size with maximum quality and clarity verses smaller file sizes but with lower quality.  Image quality is a number between 1 and 12.  Maximum settings are 8-12.



Format Options have 3 choices.  Baseline Standard is the more popular, standardized format supported by all web browsers.  This is the option you should always select.  It comes up as the default setting.  Baseline Optimized tries to optimize the color resulting in a smaller file size.  Progressive will save several 'scan' versions which go from blurry to clear when you try to load the file on the web.  Very similar to interlaced PNG files.  Baseline Optimized and Progressive versions are not supported by all web browsers so it best to stay away from these versions.  Plus we want to maximize the print quality so these 2 options don't fit for us.

So what's the real trade off between quality and file size?  To answer that, we need to experiment.  Here's a layout I made with Cheri's 'Lucky Day' kit:


I flattened the 12x12 page, did some minor sharpening and saved it with different JPEG quality settings to see what the file size would be.

Quality = 12, file size = 9600kb
Quality = 11, file size = 6022kb
Quality = 10, file size = 4132kb
Quality = 9, file size = 3020kb
Quality = 8, file size = 2300kb
Quality = 7, file size = 1669kb

Wow, that's a pretty big range of file sizes!  For print quality, you'll want to choose at least 10-12, but you can see how by increasing the quality level from 10 to 12, you more than double the file size.  When I look at the pages, I do notice that at quality levels 7 and 8, my son's face gets a little bit blotchy and the small print font gets a tiny bit fuzzier.  You can't see much difference between 11 and 12, so for my personal preference, I always pick 11 which I feel is a comfortable trade off between good quality and file size.  I do know a few folks who pick quality level 12 and then delete all their print version of the files after the layouts have been printed or save them off to a CD.  Sometimes file size and lack of hard drive space can dictate some of your saving decisions.

Just another little techno tidbit for you about JPEG files.  Hope you find these writeups helpful.

3 comments:

  1. Linda thanks for such a helpful guide. I have always wondered about the JPEG save options and different file sizes. Now I know! Many thanks =) JenEm

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  2. Great information! Thank you so much for sharing this. Shannon

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  3. This was INCREDIBLY helpful! Thank you!!!

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