Version:           1.8.0 (using KDE 4.5.1) 
OS:                Linux

Color > Color Effects > Find Edges

In using the above filter the Preview does not correctly represent the output product when the image is larger than that displayed on the screen.

In a test with my full-sized (4752 x 3186) image the results of the filter were vastly different from the previewed effect. When I processed the same image but with a reduced size to fit my screen (1500 x 1000) the preview and the output matched perfectly.

I then tried to zoom the preview to 100% to then make the adjustment ( as can be done with sharpening for instance) however this was not permitted with this filter.

I have noticed this (and mentioned it some months ago) it also does effect several similar process filters.

Reproducible: Always

Steps to Reproduce:
Color > Color Effects > Find Edges

Use an image larger than screen size. (Significantly larger for test)

Actual Results:  
Effect very 'muted', much of the line-work is lost, colors fade badly

Expected Results:  
Expect output to resemble preview.

OS: Linux (i686) release 2.6.35-25-generic
Compiler: cc