BetterPhoto Q&A
Category: Digital Files and Formats

Highest Quality Compression/Lossless Compression

Are these really lossless - or are they just less lossy? If I really could save in a lossless JPEG format it certainly would make fill keeping easier.

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January 23, 2004

My advice - if your photos are purely from a digital camera - not scanned from slide of film. Back them up as soon as possible. Save them in there original format and only work on copies. Your original digital camera files are the only proof you took the photo (should you ever need to prove it). I do not save anything in jpg - (I shoot in RAW these days). I only save in TIFF or BMP (at 300 dpi - ready for print). CD Burners and media are that cheap these days there is not reason to risk image quality by saving in a compressed format (which is what jpg is).

My belief on the quality of the jpg files for storage will depend upon how often the file is opened - but more importantly how it is saved. If you open a .jpg file over and over again and save it at a lessor value then the highest - the image quality suffers. The debate goes on and on, on this subject of lossless quality. My photos are important to me - I don't risk it.
Regards.

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January 23, 2004

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January 29, 2004

The issue with re-saving jpegs is much-misunderstood.

To (over)simplify, when you save a picture to jpeg, the jpeg compressor makes compromises as to what detail in the picture isn't really necessary, and removes that so it can create a smaller picture. This happens every time you save to jpeg, regardless of what the source image was.
In other words, if you open a jpeg, make a modification, then save it again, the compressor re-evaluates the image again, deciding what should be removed. The more times you do this, the more detail you will lose.
Wherever possible, only save to jpeg once, for the final picture.
Keep an uncompressed original to work and save to while you are manipulating the image. I use paint shop pro, and save everything in the native file format for this program.

(Opening an image will not modify the picture, and all programs open a jpeg the same).

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February 23, 2004