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Scratch Pad Exploration of a single feature or technique, illustrated with user examples

Sharpening

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  #21  
Old 08-12-2004, 03:45 PM
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T Paul T Paul is offline
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Not a teacher, but I am self-taught so I am pretty good at searching the web or my books for information. As you can see from my resources I gathered this information from all over the net. I find it nice to have all the information at your fingertips.

I'll add channels to my list of things to do.

~T
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  #22  
Old 08-12-2004, 03:51 PM
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Mosha Mosha is offline
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What can I say....just... THANKS...
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  #23  
Old 08-12-2004, 06:15 PM
W. Rose W. Rose is offline
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Great Job T. Paul,
This has really helped me alot.
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  #24  
Old 08-12-2004, 09:07 PM
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T Paul T Paul is offline
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Glad to hear that this is helpful!

If anyone else has a sharpening technique or favorite USM setting I didn't include, please feel free to add them.
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  #25  
Old 08-13-2004, 10:29 AM
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byRo byRo is offline
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Better than USM

Quote:
Originally Posted by T Paul
(from Steve A.K.A Trimoon )
This above method of using the high pass filter is something that I used a year or so ago and no longer recommend this method except for certain special effects when doing artistic renderings.
..........
Better Than USM


I saw this yesterday in the other thread ('something different') and went running to the link. I was planning to spend the weekend (wife permitting) immersed in convolutions and filter factories.

But..
Can anybody give us a jump start on the learning curve?
Is it better than USM? If so, when and how?
Is it better than high-pass? If so ,when and how?
Use custom filter, or filter factory, or something else?
etc??

Roland
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  #26  
Old 08-13-2004, 11:01 AM
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T Paul T Paul is offline
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Custom Filter

Excellent question, but one I can't answer. Perhaps someone else will be able to.

Here is a quick low down on the three filters:

From the PhotoShop help file:

Custom Filter

Lets you design your own filter effect. With the Custom filter, you can change the brightness values of each pixel in the image according to a predefined mathematical operation known as convolution. Each pixel is reassigned a value based on the values of surrounding pixels. This operation is similar to the Add and Subtract calculations for channels.

You can save the custom filters you create and use them with other Photoshop images.

To create a Custom filter:
Choose Filter > Other > Custom.
Select the center text box, which represents the pixel being evaluated. Enter the value by which you want to multiply that pixel's brightness value, from -999 to +999.

Select a text box representing an adjacent pixel. Enter the value by which you want the pixel in this position multiplied.

For example, to multiply the brightness value of the pixel to the immediate right of the current pixel by 2, enter 2 in the text box to the immediate right of the center text box.

Repeat steps 2 and 3 for all pixels to include in the operation. You don't have to enter values in all the text boxes.

For Scale, enter the value by which to divide the sum of the brightness values of the pixels included in the calculation.

For Offset, enter the value to be added to the result of the scale calculation.
Click OK. The custom filter is applied to each pixel in the image, one at a time.

Use the Save and Load buttons to save and reuse custom filters.
High Pass

Retains edge details in the specified radius where sharp color transitions occur and suppresses the rest of the image. (A radius of 0.1 pixel keeps only edge pixels.) The filter removes low-frequency detail in an image and has an effect opposite to that of the Gaussian Blur filter.

It is helpful to apply the High Pass filter to a continuous-tone image before using the Threshold command or converting the image to Bitmap mode. The filter is useful for extracting line art and large black-and-white areas from scanned images.

Unsharp Mask
The Unsharp Mask does not detect edges in an image. Instead, it locates pixels that differ in value from surrounding pixels by the threshold you specify and increases the pixels' contrast by the amount you specify. So, for neighboring pixels specified by the threshold, the lighter pixels get even lighter and the darker pixels get even darker based on the specified amount.

In addition, you specify the radius of the region to which each pixel is compared. The greater the radius, the larger the edge effects.

A while back there was a discussion on the Custom Filter in this thread

Also here are some web links that may be helpful if you want to tackle convolutions

Convolution Web Links
Creating Custom Filters Photoshop Tutorial

Convolution Corner

Convolution Kernels

Custom Image Filter

Home-made effects: Creating your own filters - lots of info here

Last edited by T Paul; 08-13-2004 at 11:17 AM.
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  #27  
Old 08-13-2004, 02:15 PM
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kbeatrice kbeatrice is offline
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Hi T. Paul, this is a great summary of sharpening methods! In the layer mask section I think that you might have accidentally swapped the brush colors:

Next add a layer mask by Option/Alt clicking the mask button at the bottom of the Layer palette. This creates a Hide All (black) mask. Use a large, soft, black airbrush on the mask to show the sharpening where you want it.

Or: create a Reveal All (white) mask by simply clicking the mask button at the bottom of the Layer palette. Using a white brush will HIDE the sharpening effect where you paint
.


Did you mean white airbrush on black for the first one and black brush on white for the second one?

Thanks again for the great summary!
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  #28  
Old 08-13-2004, 02:28 PM
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byRo byRo is offline
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Let's convolute!

Quote:
Originally Posted by T Paul
Also here are some web links that may be helpful if you want to tackle convolutions..........
Wow, who needs Google when T Paul's around!

Didn't find much in the way of answers, did find a whole bunch of questions....
Seems like I'm going to be pretty bleary-eyed come Monday.

thanks,

Roland
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  #29  
Old 08-13-2004, 03:02 PM
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T Paul T Paul is offline
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Quote:
Originally Posted by kbeatrice
Hi T. Paul, this is a great summary of sharpening methods! In the layer mask section I think that you might have accidentally swapped the brush colors:
Ooops! Thanks for catching that. That post has been corrected.
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  #30  
Old 08-13-2004, 03:04 PM
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T Paul T Paul is offline
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Quote:
Originally Posted by byRo
Wow, who needs Google when T Paul's around!

Didn't find much in the way of answers, did find a whole bunch of questions....
Seems like I'm going to be pretty bleary-eyed come Monday.

thanks,

Roland
Yes the whole convolution thing is rather confusing. I think the best plan is to use some of the examples and start experimenting on your own.
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