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file size versus quality

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  • file size versus quality


    Have what I think is probably an easy question but I can't figure it out, so I hope someone can give me a clue....
    I just went back to work for a company who THOUGHT that if I dabbled in restoration then knew all about graphic arts. Boy are they wrong but I'm trying to learn....So the question is: They want all files in EPS format and they want resolution to be at least 250-300, sounds simple but they also want file size under 1 meg so it can be emailed to vendor... My files are ending up more like 25 or 30 meg..... The resolution needs to be high enough so that when they enlarge the image it does not get pixelated...

    So for example is you email me a copy of a company logo at resolution of 72, I need to be able to give my vendor this exact same logo at 300 resolution but with result being a good quality image whether the are enlarging image or making it smaller..

    Hope this makes sense to someone..

    Thanks for any and all advice anyone has


    Oops forgot the second question which is:
    In some cases they are asking me for a vector image so in photoshop why when I add vector layers it always tells me layers will be rasterized when I try and save it as EPS format....???
    Last edited by Doriedee; 10-19-2002, 06:01 AM.

  • #2
    To answer part of your question:
    The only way an image will not lose quality as you enlarge it, is if it is a "vector" graphic. Raster images will get pixelated as you enlarge them.
    BTW, you can't transform a "raster" (bitmap) image into a vector (unless you have some program that "traces" it, but we won't go there as it doesn't usually work out).
    Your best bet (when working with bitmaps) is to set the resolution to 300 and resize the image until it meets your file size requirements.
    Keep in mind that the more colors you have, the larger the file size. When possible, changing the "mode" to "Index Color' will greatly reduce the file size.

    Just guessing about the Photoshop problem, but perhaps because you have some layers that are bitmap, it cannot be a "true" vector image, and therefore, cannot be saved as such.
    Hope this helps.


    • #3
      Donna, in perhaps 90% of cases - a 'logo' should probably be native vector and not raster format. This means originating in Illustrator, FreeHand, Draw etc.

      This will provide the small file sizes and resolution independence reqd.

      As for raster art...

      You have two choices for compression - lossless or lossy. Most lossless formats do not save that small a file (zip, lzw, jpeg2000? etc). Lossy formats like JPEG throw away some data but give you much better file sizes. Then there are choices for third party proprietary compression methods which can also help to reduce file size with or without data loss.

      You also have the option of using the channels/split channels command and emailing each separate channel of a colour file as individual emails, then the other party will recombine them (but this is not the best all round method, but it works).


      Stephen Marsh.


      • #4

        Lets see if I understood right..

        I can just take the image they emailed me (which is generally 72)
        open it in photoshop
        change to image mode
        got to resize and change resolution to 300
        save as EPS...

        Now when you say to change file size
        Im just changing pixel size for file size puposes, correct ??
        So if I saving it as approx. a 3" x 5" image and they need to enlarge to 8"x10" for printing purposes they will not lose too much quality...

        Is it really that simple ??
        Boy I hope so ..
        Been out of work for 5 months and am really hoping I can stumble along and make this work..
        After working at the same place for 30 years, getting a NEW job can be a little traumatic..

        Thanks much



        • #5
          Thanks for the reply

          Had a feeling someone would mention Illustrator, but from what I saw its almost $1000.00 and until I can prove I can do it company wont make the investment....Never heard of freehand or Draw are they a little more cost effective but just as good ??

          We are now paying someone 100.00 an image to do this work so if I can do it, it will be a big savings... had one just yesterday. logo was 3 letters of text only and they charged us 35 dollars just to recreate... ouch..



          • #6
            Not quite so simple.(I think our wires are crossing.)

            From reading your last post, I'm guessing that you need to convert the graphics to vector (so that they may be resized without losing quality).
            I haven't done any vector work in photoshop, but from the bit I've read, you would need to redraw(trace) the image to create a "path', and that "path" can then be exported as an eps-which can be resized. Perhaps someone here has worked with paths?
            After you've done this, you'll see why their asking $100 an hour.

            To my knowledge, there is no way to increase the size of bitmap/raster images, without losing quality.


            • #7
              Thanks Vikki

              Somehow I knew it couldn't be quite that simple...
              I'll keep on reading and hopefully come up with a solution....

              What you surmised is basically correct... They send a low resolution jpg and I need to either change to a high resolution tiff or EPS file (they prefer EPS) but keep it under 1 meg OR recreate as a vector file which can be resized...

              When you say to "trace" is that where having a tablet comes in handy??



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