Announcement

Collapse
No announcement yet.

Image conversion

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Image conversion

    I was looking for some information about image conversion. And then I found this. Does anyone have any thoughts on the subject?
    type document type DPI Size compression factor conversion
    Printing JPEG 300 3888x2592 0% 100%
    web fullscreen JPEG 72 1555x1037 30% 60% smaller
    web mobile JPEG 72 583x389 50% 85% smaller
    web thumbnail JPEG 72 194x130 70% 95% smaller

  • #2
    Each one of those items depends on the situation and the photo. Each photo compresses and degrades differently with lossy compressions, like JPEG. This is why applications, like Photoshop, have "save for web" functions that enable users to adjust the amount of compression to reach the best compromise between image quality and size.

    As for printing, I'd be more inclined to not use a lossy algorithm at all and rely, instead, on lossless compression.

    Comment


    • #3
      For printing, jpg is not the preferred format. Either .psd or .tif, which are both lossless.
      And as for the 300dpi and size, that is all relative. Very relative. Each print process has its own caveats on image resolution and size.

      For instance, I do wide format and for a 45' x 15' billboard I'd want an image that is maybe 25-30ppi. Note I said PPI. Image size is in pixels per inch. DPI refers to the way the ink is laid down by the machine doing the output or dots per inch of ink.
      I might be doing that billboard with an image that is 25-30ppi on a machine that lays ink down at 720dpi.

      With conventional 4-color printing your ppi would be twice the linescreen of the halftone being used to produce the 4-color print. 300ppi assumes a 150lpi, which may or may not be the case. Ask the printer. Having more ppi than you need for the line screen being used just means you have a file that is unnecessarily large. Not having enough ppi for the lpi means you will get jaggies.
      Last edited by PrintDriver; 05-27-2017, 02:26 PM.

      Comment


      • #4
        Hi Henk and welcome to GDF.

        We ask all new members to read very important links here and here. These explain the rules, how the forum runs and a few inside jokes. No, you haven't done anything wrong, we ask every new member to read them. Your first few posts will be moderated, so don't panic if they don't show up immediately. Enjoy your stay.
        Shop smart. Shop S-Mart.

        Comment


        • #5
          Originally posted by henkbanaan View Post
          I was looking for some information about image conversion. And then I found this. Does anyone have any thoughts on the subject?
          type document type DPI Size compression factor conversion
          Printing JPEG 300 3888x2592 0% 100%
          web fullscreen JPEG 72 1555x1037 30% 60% smaller
          web mobile JPEG 72 583x389 50% 85% smaller
          web thumbnail JPEG 72 194x130 70% 95% smaller
          You might as well consider the table hogwash. As already pointed out, "DPI" doesn't even apply, and JPEG is not the format for everything.

          Like a doctor dosing medications, a graphics pro makes educated decisions based on the mathematics imposed by context, application, and best practice. There is no universal solution; no lookup table. It's an interpretive process.
          Which Right? The old Right that was often right, or the new Right that's so so Wrong?

          Comment

          Search

          Collapse

          Sponsor

          Collapse

          Incredible Stock

          Latest Topics

          Collapse

          GDF A division of Mediabistro Holdings Adweek | Mediabistro | Clio | Film Expo Group Contact Us | Terms of Use | Privacy Policy Copyright 2016 Mediabistro Holdings
          Working...
          X