Re: Question re jpeg compression

Discussion in 'Digital Photography' started by Paul Furman, May 24, 2008.

  1. Paul Furman

    Paul Furman Guest

    Peter in New Zealand wrote:
    > I am aware of the issue with repeated editing and re-saving of jpeg image
    > files, and the diminishing quality this can cause. I mostly work in jpeg all
    > the time as my little humble p&s Fuji only makes jpegs anyway. I notice in
    > the options settings of my editing software there is the ability to set the
    > default compression of jpeg files. In this package it defaults to 90 (on a
    > scale from 1 to 100), but I have seen similar settings in a few other
    > programs also. The help says the higher the setting the higher the quality
    > and the larger the file. What happens if I set the default to 100? Does that
    > mean no compression at all? Without recompression would this do away with
    > the slow drop in quality over repeated saves, in effect making all editing
    > and saving lossless?
    >
    > Probably not all that relevant to the question but I am using Microsoft
    > Digital Image Standard Edition 2006 (Library and Editor). I would love to
    > know if this is possible as I love fiddling with my images, and storage
    > space is really not an issue for me.
    >
    > Thanks for any thoughts out there.


    Just to be clear, there is no damage from repeated saves unless you
    close the file between saves. Of course you are saving the original, so
    you can always start from scratch if you want to edit more another day.

    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
     
    Paul Furman, May 24, 2008
    #1
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  2. Peter in New Zealand wrote:
    []
    > If anyone has any thoughts as to why converting and storing in png
    > format might not be such a bright idea (apart from the size issue) I
    > would appreciate your comments. I feel such a beginner with all this,
    > and the knowledge and experience of many others in this group is quite
    > self evident. My grateful thanks.


    Peter,

    Unless you have the uncompressed originals (i.e. not compressed JPEGs),
    you will gain nothing by saving what you already have in PNG format. The
    JPEG loss has already happened. Next time you scan or take a photo, you
    can ensure it's lossless, and save /that/ in PNG if you wish.

    Actually, I find that a low-compression JPEG is actually good enough for
    me. I don't have time to mess with processing "RAW" format images, and I
    believe in getting the exposure correct in the camera at the time of
    taking (if possible) rather than fixing it later in post-processing.
    Perhaps that what comes from decades of taking slides!

    Cheers,
    David
     
    David J Taylor, May 25, 2008
    #2
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  3. Peter in New Zealand wrote:
    []
    > Thank you David. I might be getting just a little narrow minded on
    > this one. Maybe I need to step back a little and get a more relaxed
    > point of view. If I understand what you are saying it means that,
    > because my little camera *only* saves in jpeg format, there's not too
    > much point in converting once they are on the computer. In fact I
    > used jpeg quite happily for about four years until I learnt about the
    > issue of lossy compression. Maybe it's a case of a little knowledge
    > being a dangerous thing (smile).


    Yes, if JPEG is what you already have, you will gain nothing by converting
    to a lossless format. If your next camera offers a raw-format option,
    saving that will allow multiple post-processing from the more accurate
    master.

    []
    > I should try to be more like Cartier Bresson who pioneered the concept
    > of the decisive moment in a scene. He became almost psychic in his
    > ability to anticipate it and hit the shutter release on his ancient
    > and (to us) primitive equipment.
    >
    > Now I am rambling - please forgive me, and once again, thank you David
    > for your valuable comments.


    Oh, yes! Having an eye for a good photo, and knowing the "right" moment,
    can outweigh any of the technical stuff. I see this with my wife's photos
    all the time!

    Cheers,
    David
     
    David J Taylor, May 25, 2008
    #3
  4. Paul Furman

    ray Guest

    On Sun, 25 May 2008 19:37:31 +1200, Peter in New Zealand wrote:

    > David J Taylor wrote:
    >> Peter in New Zealand wrote:
    >> []
    >>> If anyone has any thoughts as to why converting and storing in png
    >>> format might not be such a bright idea (apart from the size issue) I
    >>> would appreciate your comments. I feel such a beginner with all this,
    >>> and the knowledge and experience of many others in this group is quite
    >>> self evident. My grateful thanks.

    >>
    >> Peter,
    >>
    >> Unless you have the uncompressed originals (i.e. not compressed JPEGs),
    >> you will gain nothing by saving what you already have in PNG format.
    >> The JPEG loss has already happened. Next time you scan or take a
    >> photo, you can ensure it's lossless, and save /that/ in PNG if you
    >> wish.
    >>
    >> Actually, I find that a low-compression JPEG is actually good enough
    >> for me. I don't have time to mess with processing "RAW" format images,
    >> and I believe in getting the exposure correct in the camera at the time
    >> of taking (if possible) rather than fixing it later in post-processing.
    >> Perhaps that what comes from decades of taking slides!
    >>
    >> Cheers,
    >> David
    >>
    >>

    > Thank you David. I might be getting just a little narrow minded on this
    > one. Maybe I need to step back a little and get a more relaxed point of
    > view. If I understand what you are saying it means that, because my
    > little camera *only* saves in jpeg format, there's not too much point in
    > converting once they are on the computer. In fact I used jpeg quite
    > happily for about four years until I learnt about the issue of lossy
    > compression. Maybe it's a case of a little knowledge being a dangerous
    > thing (smile).
    >
    > Being a type A personality I tend to be a fiddler, and I find it hard to
    > leave something alone when it's not yet perfect, but *good enough* for
    > its intended purpose. I'll just trundle on with jpeg for now, and keep
    > the issue in the back of my mind so I don't go mad on the hack and save
    > business. I absolutely agree with you that it's best to get it as right
    > as possible in the camera, and so minimise post shooting processing.
    > This is a bad habit I picked up years ago when I had my own darkroom. I
    > would take multiple shots of a subject, shortlist them from the negs,
    > and then settle on just one, which I would spend hours and hours on
    > until I had it just as I liked. Trouble is it tends to make one lazy
    > when shooting I think. Just blast off heaps on the understanding that at
    > least one will be in there somewhere that does what you want.
    >
    > I should try to be more like Cartier Bresson who pioneered the concept
    > of the decisive moment in a scene. He became almost psychic in his
    > ability to anticipate it and hit the shutter release on his ancient and
    > (to us) primitive equipment.
    >
    > Now I am rambling - please forgive me, and once again, thank you David
    > for your valuable comments.


    No real reason to convert everything. Simply make it a rule and a habit
    never to edit the original - work with a copy - then you can always go
    back and start over.
     
    ray, May 25, 2008
    #4
  5. Allodoxaphobia wrote:
    []
    > Ya, But. If you save the original image as PNG, all work you may do
    > in the future on that image will suffer no more JPEG loss as you edit,
    > crop, re-size, balance, saturate, sharpen, yaa-daa yaa-daa, _and_
    > you continue to save the intermediate work(s) as PNG. The final,
    > final step to save a selected image as a JPEG for web usage, digital
    > photo frame usage, email attachment, etc. will be the _only_ other
    > JPEG loss incurred.
    >
    > Jonesy


    As Ray say, /never/ edit the original, always work on a copy and, if you
    are being fussy, save the copy losslessly while editing - perhaps as PNG.

    Cheers,
    David
     
    David J Taylor, May 25, 2008
    #5
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