15 August 2008
File Format Basics JPEG - TWIP
Posted by
Scott under:
Tips
Photo by Scott Bourne
Most photographers deal with JPEGS either coming out of a digital camera or in Photoshop/Aperture/Lightroom when making images web ready. Unfortunately, JPEGS are a lossy form of compression. This means that the heavier the compression, the more the image is degraded. If you compress detailed images, you get more loss than if you compress soft images. Remember that once you have saved an image as a JPEG, you have compressed it. You are compounding the degradation to the image if you open it, modify it in any way, and save it again. This creates poor results, so only save an image as a JPEG once.
A JPEG’S strong point is its ability to save continuous tone better than GIF files, which is why most Web photo renderings should be saved as JPEGS.
4 Comments so far...
Aaron Says:
15 August 2008 at 11:20 am.
GIF’s are limited to 256 colors — another reason why photo renderings should never be saved as a GIF. 
Guilherme Says:
15 August 2008 at 12:09 pm.
Nice, we more or less know more or less what each file formats are for and their restrictions. But it is good to have a photography related post about it.
@Scott, I hope you talk about the advantages/disadvantages of using other formats as well as the diferences between 16bit 8bit and so on.
Thanks
JeffH Says:
15 August 2008 at 1:31 pm.
I know this is post was only aimed at discussing the basics, but it might be worth mentioning alternatives to shooting directly to a .jpg file format in the camera. Shooting so that your camera saves your images in a RAW file format will provide optimum image quality and maximum latitude for adjustment once out of the camera. Raw files are (generally) uncompressed in a 16 bit space as opposed to a compressed .jpg in an 8 bit space. If you do your editing in in Lightroom or Aperture, you never need to convert your file to any other format unless you need to send or upload a finished photo somewhere. In Photoshop, once you have edited your RAW file, you will need to save it in some format other than RAW. If you want to retain the ability to access layers you created and re-edit them at a later date, you will want to save your photo in an either .psd or .tif format, which are uncompressed, or in the case of .tif can be losslessly compressed. If you are done editing (and don’t expect to re-edit the photo a later date) and want a finished file to e-mail, post on the web or print, saving in .jpg format will work just fine.
Links - August 22, 2008 « Photo Notes: Photography by Patty Hankins and Bill Lawrence Says:
22 August 2008 at 1:06 am.
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