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Thread: JPG Compression

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    Plutonium Lounger
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    JPG Compression

    As you may know from other threads, I have recently installed PSP X (version 10) and I'm also in the process of scanning my family 35mm slides with my new Canon scanner. In making the transition from PSP 9 to PSP 10 I happened to notice that the JPG files I was saving were considerably larger than I had been saving with PSP 9. On checking my Save As options, I noted that in PSP 9 I have been using a compression factor of 40% and I can't remember where I got that value from. It may have been from a tip here in The Lounge or might have even been the default for PSP 9, I can't remember. When I checked that screen in PSP 10, the default was set for 20% compression and I admit to being thoroughly confused. I did a few temporary saves in PSP 10 at 40% and even 50% and when I "compare" the resulting images to my naked eye, I can't tell the difference.

    Would someone mind volunteering a recommendation on this topic? Is there some compression number that is "typically" used by non-professionals like me and if not, what am I sacrificing by using a higher compression percentage that I can't see with my naked eye? I don't want to necessarily sacrifice clarity of my files but at the same time it seems silly to waste gigabytes of space unnecessarily. Thanks...

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    Super Moderator jscher2000's Avatar
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    Re: JPG Compression

    If you plan to edit the image (e.g., adjust contrast or color) "people say" it is preferable to save with as little compression as possible. This reduces the possibility of gaps in your data that could create strange visible effects. When the image is "final," it makes sense to save the image in a more compact form because the software is reasonably smart about how it discards subtle detail -- as you point out, one often cannot perceive the difference with the unaided eye. Each program refers to compression differently, but 40% seems reasonable to me.

    As for wasting gigabytes of disk space, I think that's what those large external USB hard drives are for...

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    5 Star Lounger
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    Re: JPG Compression

    Hi Al

    Here are a couple of sites with info on JPEG,
    JPEG Myths and Facts
    JPEG image compression FAQ

    Have a Great day!!!
    Ken
    <IMG SRC=http://www.wopr.com/w3tuserpics/KenK_sig.gif>

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    Re: JPG Compression

    What I do is burn a CD or DVD of the fresh scanned images. NO editing, cleaning or compression. This will give me the original source. Once I start doing the cleaning and etc. I will burn current compressed copies ONLY after I am through. This allows me to always be able to go back a start over when ever I do a "O' <img src=/w3timages/censored.gif alt=censored border=0>".

    Now running HP Pavilion a6528p, with Win7 64 Bit OS.

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    Plutonium Lounger
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    Re: JPG Compression

    Interesting stuff, thanks for posting those links!

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    Re: JPG Compression

    I think that if you are planning to reedit the images at all, you should avoid lossely formats like jpg altogether, and stick with tiff or something. Each time you edit that jog, it's going to rerun that compression algorithm, and you'll lose a little bit more of the original information.

    On the other hand, I'm looking at this from the perspective of maintain quality of the images the design company I work for's image library. For most photographs, it may not make an apreciable difference.

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    Super Moderator jscher2000's Avatar
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    Re: JPG Compression

    Well, I generally take photos in JPG format, so obviously I am compromised from the outset. I do save the original in case I want to go back to it for a complete re-do. The problem with TIFF is the 4x+ file size, although PSD files make TIFF look modest by comparison. <img src=/S/grin.gif border=0 alt=grin width=15 height=15>

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    Re: JPG Compression

    With my camera I to use the jpeg format, but scanning is different. Yes, the TIFF takes up a lot of disk space, that is one of the reasons I went to a DVD burner and extrenal USB hard dives. I do not keep any of the TIFF's on my main hard drive .

    Now running HP Pavilion a6528p, with Win7 64 Bit OS.

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