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Need to know how blur filters work

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Old 08-29-2002, 03:31 PM
shag-man shag-man is offline
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Need to know.

Hello, I need to know how the blur filters work on images. Where do i need to go to find this kind of information. Also on the sharpening filters as well.


Btw. I'm a high school student. I can't buy a lot of books on photoshop. I have one or two of them.
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Old 08-29-2002, 05:41 PM
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thomasgeorge thomasgeorge is offline
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Do you mean: (1) How the algorithms work or(2) The effect of the various filters? You might try a search with the phrase " Blur Filter Effects Algorithms"....Tom
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Old 08-29-2002, 07:41 PM
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Doug Nelson Doug Nelson is offline
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The sharpening filters are easier to describe. They look at edges in the image, and anywhere they find one, they exagerate the contrast just along that edge. The various controls determine how wide an edge they look for, and how much they increase the contrast. Too much and you get the dreaded halo effect.

Blur filters are more intuitive to use, but harder to explain. They make things....blurrier Again, the controls determine the range of pixels affected and how much they're affected.
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Old 08-29-2002, 10:04 PM
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thomasgeorge thomasgeorge is offline
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You might give this link a look to begin with...
Good luck...Tom
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Old 08-30-2002, 11:02 AM
john_opitz john_opitz is offline
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Adding to the above, try here:

This is on sharpening.

By telling you this is not going to help you much. Their are some books out their on the above subject.
If you want........When "Professional Photoshop" (the one updated for P.S.7) comes out. I'll give you the one I have for P.S. 6 for free, if you want it. That might help you. E-mail me your address and I'll ship it too you...... As long as you don't live on the other side of the world.
I have to tell you though. The book was man-handled. I mean the book is falling apart. Tape and glue is holding it together. And the cd is mac formated. You can't use it on windows. But the book is still useable.......I should say readable. And if you like the book and helps you out, just donate, let's say $5 or whatever to this site. I don't know if they still have that going? But, Don't Send me the money. As this would put me in a different tax bracket for the IRS. As I don't need those problems.
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Old 08-30-2002, 09:04 PM
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Jakaleena Jakaleena is offline
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Hi Shag!

I know what you mean about not being able to buy a lot of books - the book collection I want to own would flip my budget like a Vegas Circus act!

I can usually borrow the books I need from the library, though. And if my local library doesn't have them, they get them in for me via inter library loan. It's not nearly as good as actually owning the books and having them on hand exactly when I need them, but it is still very helpful. And being able to borrow them for a while helps me decide which ones I want to spend my $$ on...
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Old 08-30-2002, 09:24 PM
Stephen M Stephen M is offline
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Shag-Man, just how good at math and programming are you?

As previously suggested, just learning how to use the tools presented by programmers is one thing - learning how programmers do this sort of thing is another!

Photoshop's custom filter is the first place where many start, before moving onto filter factory plug or more advanced plug creation toolsets. Then you can learn to write the plugs/filters in a programming language etc. It can get very deep.

I once mistakenly thought that I would like to get into Java programming, without being great at math or having a programming background...big mistake!

Who needs books when you have the internet? That's not a fair statement (I love books and reading), as a hardcopy and a nice book has many advantages over electronic media. Secondhand bookstores often have great castaway textbooks and manuals etc. The internet is fantastic for those with a budget or based in locations which do not offer the services you require. Searching many of the university, technical college or K-12 .edu websites in computer sciences and signal processing and digital image processing may be what you need for the 'nuts and bolts' stuff on how all this stuff works.

Here are some links to help answer your questions:

There are many USM and sharpening links above, the Margulis and Real World (Fraser) links do an excellent job of describing both the technical and practical aspects and there is even some links to the deeper stuff from a programming point of view in the PhotoNet links.

Although not a gaussian blur - the high pass filter is the opposite of a low pass filtering operation, which is similar or perhaps the same as gaussian blur.

Using a search engine such as google or yahoo should also do the trick, if you have some time (the above should speed things up a bit I hope).


Stephen Marsh.
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Old 09-06-2002, 04:07 PM
shag-man shag-man is offline
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Thank You for that info. Great explantion on those links everyone.
Thank You. John
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