Will I lose quality in a zip file?

Discussion in 'Digital Darkroom' started by trevor_henrich, May 4, 2011.

  1. I need to send about 20 raw or png formatted photos to a magazine company. Should I compress them in a zip, or will I lose quality?
    I'm really not sure how to go about this
  2. ZIP is a lossless compression, otherwise you couldn't zip data files or executable programs.
  3. Zip is lossless, it will not lose quality. However, all png files and some raw files are already compressed, trying to
    compress them again may actually increase the file size.
  4. different compression algorithms perform differently on different data streams. Really can't make a definitive statement other than 'try it'.
    As noted, it may slightly increase size but most likely, you'll see a marginal reduction in overall size. Many zip tools have a 'try harder' or 'compress more' option but in my experience, they suck up a huge amount of time for almost no real gain.
  5. As previous posters said, you will not lose quality with zip and may not reduce file size. What you could do is to pack several files in one .zip file to reduce handling.
    Ask the magazine company if they have a ftp server or a preferred way to receive the files.
    Otherwise you could use a service like yousendit
  6. ted_marcus|1

    ted_marcus|1 Ted R. Marcus

    I did some experimenting years ago, and discovered that setting the zip compression to "less compression/faster" actually was more effective for JPEG and similar files that are already compressed. But the difference wasn't that much. The only real use for Zip compression of JPEG or raw files is what the original poster proposes to do, collecting a bunch of files into a single archive that's easier to store or send.
  7. I used to put lots of JPEGs inside ZIP files knowing that I would get no additional compression. The only advantage is that your hard drive will read a few large ZIP files much faster than it reads thousands of JPEGs. It probably wouldn't matter much today, but in the days of 500mhz and slower processors it did help.
  8. 7-ZIP is better than ZIP, running faster and sometimes creating files more than 50% smaller.

    That said, ZIP and 7z can compress some types of RAW files really well, but not so much JPEG. And to correct an implication above, although PNG files are compressed, unlike standard JPEG, they are lossless.

    One problem with sending one ZIP is that it can become completely corrupted over the wire, whereas sending individual JPEG files (e.g. with ftp put) is less prone to massive data corruption.

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