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The best way to sharpen images for web?

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  #1  
Old 03-06-2010, 11:22 AM
Caravaggio Caravaggio is offline
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The best way to sharpen images for web?

I am sharpening some images for the web using the high pass filter set to overlay. Does doing this introduce any color fringing in the images and is it necessary to make a saturation adjustment layer to correct this? Thanks.
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Old 03-08-2010, 09:36 AM
edgework edgework is offline
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Re: The best way to sharpen images for web?

Quote:
Originally Posted by Caravaggio View Post
I am sharpening some images for the web using the high pass filter set to overlay. Does doing this introduce any color fringing in the images and is it necessary to make a saturation adjustment layer to correct this? Thanks.
Do you see any fringing? This kind of issue depends on the image.

One thing you might try is sharpening a duplicate layer, then putting it in Luminosity mode. That will give you the detail without any color drift at the fringes.

High Pass in Overlay mode might not be your best choice. Linear Light at 50% has been cited in some tutorials (By Ro, who's always spot on), as the accurate set-up.
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Old 03-08-2010, 10:37 AM
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flexmanta flexmanta is offline
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Re: The best way to sharpen images for web?

Linear light 100% is better when you obtained the high freq layer through the apply image command instead of the high pass filter which gets confused by pure black and pure white.
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Old 03-08-2010, 12:01 PM
Caravaggio Caravaggio is offline
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Re: The best way to sharpen images for web?

Thank you edgework and flexmanta for your responses and I will try each of your ways of sharpening.

Flexmanta, I have somewhat followed the postings on retouchpro and modelmayhem about separating the image into high and low frequency channels but have to admit I am still a little confused and there seem to be many variations on the technique. Could you explain yours in a step by step way as I would like to learn or point me towards a tutorial? Thanks.
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Old 03-11-2010, 12:40 PM
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Pictus Pictus is offline
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Re: The best way to sharpen images for web?

See this http://members.ozemail.com.au/~binar...ersharpen.html
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Old 03-11-2010, 02:13 PM
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Cuervo79 Cuervo79 is offline
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Re: The best way to sharpen images for web?

The separation technique can be used for sharpening and for skin retouching. I think that is why you're getting confused. Specially because in order to do any step you have to blur one of the copies.

When sharpening 16 bit images I do the following:
Stamp visible
Duplicate the stamp visible layer
Select the first layer (the one you created with the stamp visible command)
Use gaussian blur at the value of your choice (I work with 8mp files so I normally work with values from 1.8 to 2.5)
Select the duplicate of the stamp visible layer
Go to image>apply image
In the Layer dialog, select the bottom layer which you blurred (the one you created with the stamp visible command)
In the Blending dialog, choose add
Check the invert box
Enter '2' into the Scale box, and '0' for the Offset
Press OK
Delete the layer you used the gaussian blur on
Select the layer that now looks like the high pass filter was done in change the blending mode to linear light.

After that I normally add a mask and hide everything but the stuff I want the sharpening to be applied to.
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Old 03-11-2010, 11:24 PM
Caravaggio Caravaggio is offline
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Re: The best way to sharpen images for web?

Thank you Pictus and Cuervo for your responses. Pictus, I am still trying to get my brain to understand all the information that is contained in your link. I will have to read it a few more times to try to understand it all.. Cuervo, thanks for explaining the separation technique so clearly.

Unfortunately the files I am trying to sharpen for the web are only 8 bits. I was only given 8 bit images and never had the raw files. There is no point in converting an 8 bit image to 16 to do your sharpening technique because the information is already lost, right? What would be the procedure for sharpening when the image is only 8 bits?

A stupid question, Cuervo, but when you said you worked with 8mp files that means your images were shot using an 8 megapixel camera?

Thanks so much for your help.

Last edited by Caravaggio; 03-11-2010 at 11:35 PM.
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Old 03-12-2010, 12:22 PM
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Cuervo79 Cuervo79 is offline
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Re: The best way to sharpen images for web?

with an 8bit image the difference is just in the apply image stage

In the Blending dialog, choose Subtract.
Enter '2' into the Scale box, and '128' for the Offset.
Preserve Transparency, Mask, and Invert should not be checked.

Everything else is the same.

Yes I shoot with an 8mp camera, I mentioned this because the values will change depending on how big or small the photo you're retouching are. Bigger photos need a bigger value and smaller photos need smaller values
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Old 03-12-2010, 02:43 PM
Caravaggio Caravaggio is offline
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Re: The best way to sharpen images for web?

Thanks a lot Cuervo. I am going to try it out.
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