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This is Interesting: Free Magazines for Graphics designers and webmasters
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  09-23-04 - 12:22 AM
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Jeff Gorman wrote:
>
> Help please!
>
> Writing freelance in a woodwork magazine, I am trying to render a tracing
of
> a toilet mirror, wanting to create a smooth diagonal gradient from white t
o
> grey, (as one does to a photo when wishing to remove unwanted reflections)
> but trial prints show a fan-like effect with the transitions between tones
> being very evident.
>
> Could an experienced PSP 8er kindly tell me how to do better than this
> please?
The bottom line is, I think, that you are saying your
gradient has visible steps. There are typically two reasons
for this. The first is that, in Windows Display Properties,
your display is set to 16-bit High Color and not 24-bit or
32-bit True Color. Since there are fewer discrete colors
with a 16-bit representation, your gradient will have steps.
The second reason for problems is that your gradient has
very few color gradations and covers a large number of
pixels. As an extreme example, imagine a grey gradient
ranging from 128 to 130 spanning a 300 pixel wide image.
On the very left the color will be grey 128 and on on the
very right it will be 130. In the middle of the image it
will be 129. Since there are no greys between 128 and 129
or between 129 and 130, there will be a step at pixel 100
between a region filled with grey 128 and grey 129 and a
second step at pixel 200 between a region filled with
grey 129 and grey 130. Your actual situation is unlikely
to be as extreme as this but it could be fundamentally
similar. The way to deal with this is threefold: (1) make
the gradient span a larger range of color; (2) make the
gradient span a smaller number of pixels (which makes any
steps narrow and hard to see); and/or (3) add a little
monochrome noise (a few percent) to the steps to disguise
them and make them much less visible.
> I recall being able to do this with a simple drag in Photoshop 5 Lite and
> Elements 1, but don't want to have to re-load Elements and mess about
> between two applications if I can possibly avoid it.
It has nothing to do with what tool you use to create the
gradient. The issue is either your display setup or the
characteristics of the gradient.
> I have it set up so that image information reports 24/16million colours at
> 300ppi.
That's fine. The resolution is irrelevant since it only
affects how the width in pixels of your image is mapped to
a width in inches when you print the image. What matters
is how many pixels there are in the image. The more you
have and the smaller the color range in the gradient, the
more likely are visible steps. Moreover, just because the
image is in 24-bit color does not mean that your display
is set to show all those colors. If it isn't then you
will see steps too.
> Jeff
> --
> Jeff Gorman, West Yorkshire, UK
> Email: username is amgron
> ISP is clara.co.uk
> www.amgron.clara.net
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