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gradient isn't uniform

Jun 8, 2012 12:50 PM

Hello,

 

When I create a simple gradient in Illustrator, it isn't uniform. I see lines of black shades. Why?

 

 

gradient.png

 
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  • Currently Being Moderated
    Jun 8, 2012 6:27 PM   in reply to baumacs

    Is this a trick question?  A gradient is the same as a blend from one color into another color over an area.  If you want a uniform color, use a flat fill color like the 50% K you've got in your color palette.  A gradient is not uniform because it is not uniform, except in one direct in a single area ( i.e., your gradient palette as shown above ).  I'm getting a headache.

     
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  • Currently Being Moderated
    Jun 9, 2012 4:35 AM   in reply to baumacs

    The pattern you're seeing is referred to as gradient banding. In principle, think of it like this:

     

    A Photoshop gradient is an array of a fixed number of pixels, each a specific tone. So the number of tone steps remains the same, regardless of how the image (the fixed set of pixels) is scaled (resolution dependence).

     

    So Photoshop (PhotoPaint, whatever) says something like: "Color the leftmost image pixel 100%. Color the second image pixel 99%. Color the third image pixel 98%..."

     

    An Illustrator gadient is a mathematical command to transition from one tone to another over a distance. So the number of steps rendered between the starting and ending tones specified  is dependent upon the mechanics of the current output device (resolution independence). Your monitor is an output device. Think of it as a low-resolution printer. The number of bands you see on your monitor is different from the number of bands that will occur in print.

     

    So Illustrator (CorelDraw, whatever) says something like: "Color the left end of this object 100%. Color the right end of this object 90%. Fill in between with as many steps as you can handle."

     

    Understand: That does not make raster images immune to banding in print. Banding occurs in raster images just as it does in vector paths. Just because a raster image file may specify a thousand discrete tones, doesn't mean the output device can actually render a thousand different tones. So in both cases, the number of steps in the rendered grad is limited to the capabilities of the output device.

     

    Just because your Photoshop grad appears smooth on your monitor doesn't mean it won't appear banded in print.

     

    Just because your Illustrator grad appears banded on your monitor doesn't mean it won't appear smooth in print.

     

    Don't confuse vector grads with vector blends. They are two different constructs. Vector blends interpolate a discrete number of intermediate paths, therefore a discrete number of tones.

     

    JET

     
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  • Currently Being Moderated
    Jun 9, 2012 5:32 AM   in reply to baumacs

    Save the Illustrator file as pdf and open it in Acrobat and see if your result is more like what you expect to see.

     
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  • Currently Being Moderated
    Jun 9, 2012 6:43 AM   in reply to baumacs

    I noticed that the gradient banding is only when the gradient in Illustrator is grayscale, if I put another color, looks perfect. Why?

    Think of how colors are constructed: They are "built up from" values of several "primary colors" (especially in print). Your monitor doesn't have individual rows of hardware pixels colored for each of the 16.7 million colors that can be rendered by them. It just has three rows: red, green, and blue. Each of those "primary colors" has its own grayscale ramp. There is a separate image (channel) sent to each of those three primary colors. Each of those images is actually a grayscale ramp. The steps (bands) in the image sent to the red channel does not have to correspond to those in the image sent to the blue channel, and so on.

     

    So when your monitor paints a gradient that consists of differing periods of steps for each of the three primaries--you are simply viewing more bands, so the bands are smaller and therefore less evident.

     

    The same thing happens in print. But unlike your monitor, the bands are in fact further "mixed up" by the fact that the primary ink colors (CMYK) are printed at different angles. So again: what you see on your monitor does not exactly correspond to what will be seen in print. This is true whether you are viewing a TIFF, a JPEG, a PNG, text, or vector paths, and whether you are viewing those objects in Acrobat, Photoshop, Illustrator, a web browser, or whatever. If you're viewing it on a monitor, you are always viewing it in RGB, and you are always viewing it as rendered by the simple, neat, horizontal rows of square hardware pixels, not as the rosettes of different-size, differently-angled, roundish clusters of color-separated ink dots on paper.

     

    What is the best way to spend a gradient logo made ​​in Illustrator to Photoshop?

    The best way would be to simply render your grads in Photoshop after importing the paths and converting them to pixel selections (which is really what's going on, despite all the various smoke-and-mirrors features for getting something from a vector drawing program to a raster imaging program). That's not necessarily always the most practical way. Beyond that, specifics would depend upon...the specifics.

     

    And in the rasterization options I have 600 ppi.

    The rasterization options where? You can't get good answers in an online forum without at least trying to adhere to the terms of the program, and refering to the specific steps you are performing.

     

    With so general a question, you are effectively asking for a crash course in the differences between raster and vector graphics and what occurs in rasterization. Generally speaking, you have control over the number of pixels to which a vector graphic is rasterized. And when it's all said-and-done, a Photoshop document has only one PPI (number of pixels) to which everything in it is rasterized. That's the difference between the resolution-independence of vector graphics and the resolution-dependence of raster graphics.

     

    JET

     
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  • Currently Being Moderated
    Jun 9, 2012 10:22 AM   in reply to baumacs

    I get a different result than you do/ How large is you gradient filled path?

     

    Illustrator

     

    8.5x11 full page radient

     

    Screen Shot 2012-06-09 at 1.12.57 PM.png

     

    As a pdf

    Screen Shot 2012-06-09 at 1.12.34 PM.png

     

    As a tiff opened in Photoshop

     

    Screen Shot 2012-06-09 at 1.18.42 PM.png

     
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  • Currently Being Moderated
    Jun 9, 2012 1:49 PM   in reply to baumacs

    I made this post right after I made my previous post but for some reason it did not actually get posted  even thought it appeared on my computer?

     

    How are is it being printed? If Inkjet or other rgb device then use rich black and not just the K channel. If being printed CMYK and it is a four color job use rich black as well and on jsu the K channel. NMake the printer aware of the problem.

     

    However I printed it out on my Inkjet and there is banding.

     
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  • Currently Being Moderated
    Jun 10, 2012 5:58 AM   in reply to baumacs

    I think I'll make a color proof the next week to see how it goes.

     

    Always the thing to do in any print-destined project of significant cost/run-size, when you have doubts about what you've done re grad banding or other technical concerns. The proof is always in the pudding, and the pudding is what matters.

     

    JET

     
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