CHALLENGE! Halftone filter problem

[mistercitizen]

I'm stumped on this. It is very strange.

I've tried everything and still do not understand why photoshop is doing this. To summarize, it appears that this filter is giving different effect, purely because I change the canvas size. (selection and settings do not change)

I'm using a two channel multi-channel file, and am trying to achieve a high-contrast effect (similar to a screenprint look) using the Halftone Pattern filter. The filter settings I am using are: Size 2, Contrast: 47, Pattern: Line.

I apply the filter to one channel only (which has an image which I've increased the contrast, to deliberately blow-out the white areas). The other channel is just a flat block of background colour. The problem is that this filter applies itself in a horizontal manner only - and I want an angled pattern.

So I have rotated the image channel 45 degrees and then applied the filter as before. Which works great and gives me the effect I want.The problem is because I have rotated the image 45 degrees, the corners of the image now exceed the canvas, and when I rotate the image back to it's original angle, I've lost the corners of the image.

Here is that image:

http://www.photoshoptechniques.com/forum/attachment.php?s=&postid=82971

So why don't I just increase the canvas size before rotating the image?

Well I did, but the strangest thing occurs when I apply the filter (same setting and selection as before). The filter acts quite differently, most notably in the (deliberately)blown out areas of "white". Before increasing the canvas size, the line pattern would taper into nothing in these areas. However, after increasing the canvas size, these areas become thick lines, instead of tapering to approxiamate the tonal value (white) before having applied the filter.

Like this:

http://www.photoshoptechniques.com/forum/attachment.php?s=&postid=82972

Why is this happening? I haven't changed any settings. It's driving me crazy!!!

Any tips on how to get around this would be greatly appreciated!

 

[kylebellamy]

Hey Fancy meeting you here! lol

I did some seraching and found an article that detailed all about halftones and digital ones and it suggested this process instaed of the one your using:

Quote:
If you then convert the grayscale images to monotone bitmaps using the Image > Mode command you are presented with a dialog in which you can choose to halftone the image and a sub dialog in which you can set the ruling, angle and shape. Normally you want to minimize the visibility of the halftone but we want to make it clear so we can set a crude screen ruling of 12 lpi, an angle of 90° and a square dot shape. The result is a solid black and white image but which clearly gives the appearance of the original's grayscales.
End Quote

Here's the full article, very interesting reading actually.

http://www.designer-info.com/master...-info.com/Writing/understanding_halftones.htm

http://www.kylebellamy.com

 

[mistercitizen]

Hey Kyle!

It's funny you should mention the convert-to-bitmap method.

I was actually working on another image today, doing something quite different, and I accidentally stumbled upon the very same thing! Made my day, that's for sure.

Sorry to have stolen you thunder there - although, I'll add that if I hadn't come across it by chance, I would have been jumping up-and-down for your post!

You see, I'm used to using an older version (4.0 eek!), so this feature is new to me. Some very nice effects can be achieved throught the various halftone settings.

With regards to the strange behaviour of the filter (as detailed in my first post), apparently all filters use data from outside of the selections to calculate the effect of the filter.

Thanks once again Kyle, you are a pillar of knowledge! I learn so much on this forum - I wish I knew about it years ago.

 

[kylebellamy]

On a side note, I just upgraded to the entire CS package for $500 (InDesign, Illustrator, Photoshop and Acrobat) just for owning an old copy of Photoshop. Fantastic deal!

http://www.kylebellamy.com

 

[mistercitizen]

Hmmm, great deal indeed. I'll look into that.