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Illustrator, Drop Shadows and DRES

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  • Illustrator, Drop Shadows and DRES

    Contrary to popular opinion, not everything created in Illustrator is scaleable. Many of the things you can do using Filters and Effects are actually Raster based imaging.

    Many of you may have noticed you can create fuzzy drop shadows in two ways.
    As a Filter and as an Effect. It is very important to realize that drop shadows are created using raster, not vector, imaging. It is also very important to know how the output resolution of that raster effect is controlled.

    Under the Effects menu is a flyout for your Document Raster Effects Settings. Before you even begin your design you should check that this is set at a proper output resolution based on the size and scale of your document.
    If your printer wants your files at 100% final size at 300dpi final size, set it at 300dpi
    If your printer wants your files at 25% of final size at 300dpi at final size, set it at 1200dpi.
    Don't make the output dpi larger than your printer requests. Not only will your illustration take longer to redraw, it takes longer to RIP.

    You can change the resolution of a fuzzy Drop Shadow if it is created as an Effect. You cannot change it if it is created as a Filter.

    The top part of this image shows two fuzzy drop shadows created with the DRES set at 35dpi. They look the same.

    Suppose you needed to increase the resolution of your document for a larger sized output. The bottom two squares show what happens when the DRES is changed to 300dpi. Nothing happens to the Filtered Drop Shadow while the Effect Drop Shadow resolution has changed appropriately.
    Attached Files

  • #2
    Great informative post, you should stickie it in the Illustrator stickie.
    "You're just jealous because YOUR hat doesn't have a clock in it!"


    • #3
      Very useful, thank you


      • #4
        excellent info PD, thank you for sharing.
        "It's never too late to be who you might have been." - George Eliot


        • #5
          Great job explaining the difference PD.
          "Lucy, you got some 'splainin' to do!" - Ricky Ricardo


          • #6
            I would also like to point out that there is nothing in the filters and effects menus which can't be duplicated with blends and masks (except of course for the raster image editing filters, like color adjustment). These can then be expanded to allow for true vector output...
            Ned Yeung, A.C.E.


            • #7
              Care to offer up some examples, Ned?
              "Lucy, you got some 'splainin' to do!" - Ricky Ricardo


              • #8
                Well, simple example is shadows and highlights... They are just color blends between lighter colors and darker colors. For instance, to create a sphere using the 3D effects tool, you create a half circle, then revolve it. All that illustrator does is to apply a color blend at the highlight spot, from a light/white colored circle blending into a larger one that's the same color as the base circle. Then it applies shadows by blending from a darker color within a thin crescent shape to a larger one, along the edge that's away from the highlight. This shape is accomplished easily by using the subtract or intersect tools in the pathfinder, with copies of the original shape.

                Perhaps I can show this visually... I'll try to throw something together - after I eat.
                Ned Yeung, A.C.E.


                • #9
                  I don't particularly like blends in Illustrator either because again, unless you over-estimate on your blend steps, you can't scale the image up. This isn't much easier to fix than Filtered drop shadows. Wellllll...maybe a little easier. No real parameter guessing. But annoying.

                  And they are blended steps. You will get pronounced banding at larger sizes.


                  • #10
                    Well, that's when objective planning of design comes into play. When you're desiging for billboards, you simply don't use blended art, or if you do, you use an incredible number of steps. 255 steps will go a long way in anything short of large format.

                    Also, if you start with un-expanded AI files, you can always choose a new amount of blend steps when you expand the file, if you're going to save it for a larger (or even smaller) print.

                    I do like to expand appearances before exporting EPS files, to save trouble down the road, but I always keep more editable files in AI form as well.
                    Last edited by Ned; 02-10-2007, 07:55 AM.
                    Ned Yeung, A.C.E.


                    • #11
                      There's probably a formula, I'm guessing, right Ned, for how to calculate the number of steps in the blend? I seem to recall seeing something like that back in the day before there were all these fancy schmancy effects.
                      "Lucy, you got some 'splainin' to do!" - Ricky Ricardo


                      • #12
                        Ned, there's a lot of folks out there today don't keep editable things. Sad fact. They don't teach the 7P theorum any more. Every designer should have to work at a printer for a year before they are given a license to drive.

                        Every once in a while someone comes up with a really, uh, novel way to mess up a file. I've got one now that has us going, 'Huh?'.

                        <proper prior planning prevents p*s-poor performance>
                        Last edited by PrintDriver; 02-10-2007, 07:51 PM.


                        • #13
                          Most definitely, PD... Nothing drives me crazier faster...

                          Urstwile: There is a formula, but I don't know off-hand what it is. It has to do of course with the size of the blend. Something like anything over 10% of the blend length for a step will create visible banding. That doesn't sound like the right figure to me (I think you'd be able to see banding at smaller than that!), but that's the idea...
                          Ned Yeung, A.C.E.


                          • #14
                            If you type 'Blend Formula' in Illustrator Help, it gives you the formula there. It's something like,

                            To calculate the maximum blend length for gradients

                            Illustrator calculates the number of steps in a gradient based on the percentage of change between the colors in the gradient. The number of steps, in turn, determines the maximum length of the blend before banding occurs.
                            Select the Measure tool , and click the beginning point and the endpoint of the gradient.
                            Note the distance displayed in the Info palette on a piece of paper. This distance represents the length of the gradient or color blend.
                            Calculate the number of steps in the blend using this formula:
                            Number of steps = 256 (number of grays) X Percentage change in color
                            To figure out the percentage change in color, subtract the lower color value from the higher color value. For example, a blend between 20% black and 100% black is an 80%—or 0.8—change in color.
                            When blending process colors, use the largest change that occurs within any one color. For instance, take a blend from 20% cyan, 30% magenta, 80% yellow, and 60% black to 20% cyan, 90% magenta, 70% yellow, and 40% black. This indicates a 60% change, because the greatest change occurs in magenta—from 30% to 90%.
                            Using the number of steps calculated in step 3, see if the length of the gradient is larger than the relevant maximum length indicated in the next chart. If it is, reduce the length of the gradient or change the colors.

                            Then a big chart
                            'If you can't impress them with your intelligence, baffle them with your bullsh*t ' - a great thinker.


                            • #15
                              Yes. And please note where that chart stops. 256 steps in 7.7 INCHES.

                              Now figure for 40 feet...
                              Oh, wait, Illustrator's max steps in a blend is 1000....? Now what?

                              None of the program developers ever think over 11" x 17" even though they make an 18 FOOT artboard..

                              If you specify the blend to be smooth rather than stepped, the blend is fixed at 256 steps no matter how big it is.

                              Edit: note in 220" (llly's max artboard size) 1000 steps would show 1/4" banding. So your 40' billboard or scenic element would have 1/2"+ bands. Viewing distance is key.

                              A safer bet may be to work at your printer's dpi suggestion and create your gradient in Photoshop. Some color combinations will band no matter where you create them. The banding in this case may be an artifact that has nothing to do with steps or resolution. It is how the large format printer rips interpret the color data.
                              Last edited by PrintDriver; 02-11-2007, 10:12 AM.






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