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Re: [MedievalSawdust] OT: Digital Camera?

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  • Tim Bray
    We re getting pretty far astray from sawdust here, but there seem to be some misconceptions about digital imagery. While it is true that compressed formats
    Message 1 of 2 , Feb 28, 2005
      We're getting pretty far astray from sawdust here, but there seem to be some misconceptions about digital imagery.   While it is true that compressed formats like JPEG cause some loss of information (quality), this is not the reason why drugstore-scanned images have poor appearance.   Digital cameras usually save images in JPG format, too... The problem is that images scanned at the store _start out_ with lower quality - they are scanned from a small source (4x6 print) by low quality equipment, and saved at a low resolution.  (At least, the ones I got certainly were.  Maybe things are better now...)

      It is quite correct that you can do better by scanning the images yourself.  Scanners are cheap nowadays and you can get good quality results for very little investment.  You are still stuck with the original photo size and quality, though; for original photos, nothing beats a digital camera.  They have also become so cheap that you can pay yourself back in savings (avoided cost of film developing) pretty quickly.

      Computer monitors usually display at a resolution of 96 dots per inch (dpi) or less; most scanners operate at 300 dpi or more.  So, without doing any image adjustment, what you see on the screen might be larger than what you scanned (depending on your display settings)... but there is no more detail created in this process, so the larger image will usually look very poor.  All you are doing is magnifying the original, flaws and all.  When you reduce the image size back down to something that fits onto a screen, apparent image quality improves.   

      Bottom line:  Having your prints scanned to a disk by the photo developer is quick and convenient, but may give you lower-quality images than if you scan the prints yourself, and neither method will be as good as taking digital images in the first place.  Images from all three sources will undergo some loss of information as you edit them, a result of the file compression routines, and this effect will be much worse with those images that start out poorer to begin with.  And all of this may be moot if you only need a 400-pixel-wide image for a Web page!


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