2 Replies Latest reply on Jan 10, 2013 8:07 AM by Gernot Hoffmann

    Paths flatness device pixels -if no value is placed in box is it then defaulted to .2 pixels.

    NodL Level 1

      Paths flatness device pixels -if no value is placed in box is it then defaulted to .2 pixels. The STD for our situation requires placing 1 pixel for the flatness.

      These are 300 dpi images & as I understand for the web only. I do not understand why 1 pixel is so important as it must be placed in the field manully for every image. 

       

       

      What would be the difference if no # or 1 pixwl is placed in the area - for both web & print.  Pls explain.

       

      Thank-you

        • 1. Re: Paths flatness device pixels -if no value is placed in box is it then defaulted to .2 pixels.
          c.pfaffenbichler Level 8

          Quote from the CS4 reference:

          For Flatness, leave the flatness value blank to print the image using the printer’s default value. If you experience printing errors, enter a flatness value to determine how the PostScript interpreter approximates the curve. The lower the flatness value, the greater the number of straight lines used to draw the curve and the more accurate the curve. Values can range from 0.2 to 100. In general, a flatness setting from 8 to 10 is recommended for high-resolution printing (1200 dpi to 2400 dpi), and a setting from 1 to 3 for low-resolution printing (300 dpi to 600 dpi).

          • 2. Re: Paths flatness device pixels -if no value is placed in box is it then defaulted to .2 pixels.
            Gernot Hoffmann Level 3

            As far as I know:

             

            1. The parameter flatness is used in Photoshop only for clipping paths.

            2. Clipping paths are used by output devices like printers.

            3. Clipping paths are in  programs like Photoshop or InDesign smooth Bézier curves.

            4. dpi (dots per inch) refers to output device dot resolution (not ppi!), for instance

                1200dpi for an inkjet or toner printer and 2400dpi for an imagesetter for offset

                printing.

            5. Rendering the clipping path, the smooth Bézier path is replaced by a sequence

                of straight line segments.

            6. The max. deviation from the smooth Bézier curve is defined by flatness

                For  2400 dpi we have approximately 0.01mm dot distance. Flatness=10 means,

                that the accuracy is not worse than 0.1mm. Fairly sufficient for a clipping path,

                but more important is: the path appears smooth despite its rendering by a polyline.

            7. No value for flatness will result in printer default settings, which are derived

                from the actual resolution in dpi.

            8. flatness is used for any rendering of vector paths by PostScript devices, for

                instance for vector graphics by InDesign or Illustrator.

            9. All this is not applied in Web images. The mentioned "300dpi images" may be

                (correctly named) "300ppi images", but that's irrelevant. Only pixel numbers

                count, because one source pixel is represented by one monitor pixel.

                (Let's hope that the images are not scaled by the browser using width and height

                with new numbers, which results in ugly resampling by nearest neighbour)

             

            Best regards --Gernot Hoffmann