eliminating moire in photoshop

[willisnr]

Does anyone know a specific technique for this? I have a particularly bad moire pattern on an image of a fireguard (wire mesh). I have tried (in Photoshop) to blur specific channels, and also tried to use gaussian blur / color mode, to no avail. The production manager suggested stochastic screening, but I have never encountered this technique except in a lecture hall at University - it involves an irregular dot pattern as a filter to eliminate the moire pattern - how does this work and how is it applied in a pre press environment?

We are going to try to increase the lpi through the ctp, but I don't think this will get rid of the moire completely, also it will effect the whole page, which might have poor results. Hopfully it can be eliminated in Photoshop.
Cheers
Will

[clod]

Using stochastic will eliminate any moir? that is associated with conventional screening angles either conflicting with each other or the subject matter, bit I'm unsure what affect it would have on an image with moir? caused by the capture. Can you see the moir? pattern in Photoshop viewed at 100%? If so, I guess I don't know what affect stochastic would have on it...it may try to reproduce it as detail, but I'm not sure.

You could try this:
Filter>Noise>Median (use smallest radius you can get away with)
then try to add some USM back to it (changing your layer mode to luminosity may help here to avoid color shifts/halos).

Of course if you can re-scan at larger size/resolution, so much the better.

[willisnr]

Thanks for the advice, the filter worked but did not entirely eliminate the problem. The image looks like it's beyond salvage unless we re-scan it.

I have run a proof off as-is, hopefully the client will be willing to pay for a re-scan. Probably won't though - quality doesn't seem to be an issue anymore.....

[almaink]

Try the gaussian blur filter an setting of .8-.9 seems to work well.

[DCurry]

In addition to the other tips, make sure the image is not scaled at all in the layout app. Do any scaling in Photoshop and import it at 100%.

[willisnr]

Thanks for all the advice, the client passed the proof off clean, I imagine that they didn't even look at the image in question!

I will definitely bear in mind the comments above for next time moire appears, thanks again.

[Eyetech]

Stochastic screening, according to my limited knowledge on the subject, is applied at the output stage via $$$ add-ons to RIPs.

And I don't know of any filter that works within PShop to create a such an embedded screen....but...I would love to know if there is one out there.

[willisnr]

Found this tip, basically using gaussian blur (as previously suggested) and the history brush / color mode. Although it's not a filter, I think it's a pretty handy technique - I use a similar technique to remove dust and scratches.

www.roosphoto.com/Free/ColorMoireFix.pdf