Photoshop 效果一問

RGB模式下進行,在相片copy上一層新layer,將tool box上的foreground同background填上黑白色,然後按Filter>Sketch>Halftone Palette,會出Halftone Palette對話框,最低一項選上　line　,size可按1 或 2(視乎相片的pixel大小,數值越大橫線越粗),Contrast建議選0 或 1(數值越大橫線越銳利),完成後該layer Opacity40-60%,可選overlay/hard light或luminosity(視乎相片顏色),便應是您想要的效果

actually, what I always do is use Photoshop texture to do effects ...
You want to do Banding effects, you just need to create a PSD file in your Texture folder, gray color like the one "LINES.PSD"
and use it in your texture ... very simple
for example, use this image
http://bureau.comandantina.com/archivos/Stripes-1.jpg
gray scale it first and save it as BANDS.PSD in your \Texture folder of Photoshop,
then using Filter->Texture->Texturizer->load Bands.psd and you can see it will work exactly like you want it to be.
hope it help