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Apply Image and WTF?!

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  #1  
Old 01-29-2010, 03:53 AM
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ApWizard ApWizard is offline
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Apply Image and WTF?!

Hi guys,
so here is the deal:
• document size > ~8Mp;
• document content > product photo, pure white all around it.

the steps:
- make 2 copy;
- Blur the first one (in my case 50px radius);
- Apply Image on the second duplicate (Add - invert - scale: 2 - offset: 0) the first blurred one;
- the preview looks fine;

the final rendering, after clicking ok, display white blocks where large chunks of pure white was.
This failure happens only if large areas of pure white surround the object but if I modify the pure white to another color (or to not pure white) or the document size is really small all is fine.
Replacing this Add operation with a Subtract (changing the parameters to simulate an Add) works fine.

WTF?!
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  #2  
Old 01-29-2010, 04:21 AM
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Re: Apply Image and WTF?!

Are you working 16bits or 8bits? That makes a difference.

8bits: subtract, scale 2, offset 128

16bits: invert, add, scale 2, offset 0

Also, why do you think blurring 50pixels out of a 8Mp will do you any good? See, freq separation has an advantage which is separating big flaws from good skin. That you will achieve by blurring in the 10-20 pixel range. Blurring 50pixels will only get you 2 layers. One full of everything, and another one full of, well, nothing but a splotch of color. I somwtimes work with 39Mp images from a digital back. I have never blurred more than 20 pixels for a frequency separation. And when i work with my 15Mp Canon, i normally blur 10pixels. That way I can D&B the high freq layer, and on the low freq layer i can do all sorts of things. From color mode painting, to cloning, because that's where the color flaws are left when you blur responsibly.
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Old 01-29-2010, 04:33 AM
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Re: Apply Image and WTF?!

Quote:
Originally Posted by flexmanta View Post
Are you working 16bits or 8bits? That makes a difference.

8bits: subtract, scale 2, offset 128

16bits: invert, add, scale 2, offset 0
The failure happens in both 8bit and 16bit, the procedure you writed in bold is what I do. Subtract works fine, Add do not work.

I will post a screenshot as soon as possibile.

Quote:
Originally Posted by flexmanta View Post
Also, why do you think blurring 50pixels out of a 8Mp will do you any good? See, freq separation has an advantage which is separating big flaws from good skin. That you will achieve by blurring in the 10-20 pixel range. Blurring 50pixels will only get you 2 layers. One full of everything, and another one full of, well, nothing but a splotch of color. I somwtimes work with 39Mp images from a digital back. I have never blurred more than 20 pixels for a frequency separation. And when i work with my 15Mp Canon, i normally blur 10pixels. That way I can D&B the high freq layer, and on the low freq layer i can do all sorts of things. From color mode painting, to cloning, because that's where the color flaws are left when you blur responsibly.
Frequency separation is not my target here nor the editing purpouse you assume I'm doing
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Old 01-29-2010, 04:53 AM
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Re: Apply Image and WTF?!

Let me guess.... turning a brunette into a blonde?
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Old 01-29-2010, 05:02 AM
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Re: Apply Image and WTF?!

Quote:
Originally Posted by flexmanta View Post
Let me guess.... turning a brunette into a blonde?

ahahaha no no
That's a super-awesome-topsecret-experimentingnewwaysofdoingthings retouching tricks :°D

The pure white problem remains even without the blur, is a pure white related thing.
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  #6  
Old 01-29-2010, 05:07 AM
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Re: Apply Image and WTF?!

What, the blonde hair thing is a secret? Haha... i did it recently for on of those friends who wants to see her in a different hair color and knows you can photoshop. I thought of it as the best way to separate the hair from it's color.

Yeah, if it is pure white what's causing the problem, what happens if you level it down one single value so it becomes pure almost-white?
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  #7  
Old 01-29-2010, 05:12 AM
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Re: Apply Image and WTF?!

Quote:
Originally Posted by flexmanta View Post
What, the blonde hair thing is a secret? Haha... i did it recently for on of those friends who wants to see her in a different hair color and knows you can photoshop. I thought of it as the best way to separate the hair from it's color.
Clearly not, brunette to blonde is'nt the target; I've just write "hahahah no no" it means: no, brunette to blonde isn't what I'm doing.

Quote:
Originally Posted by flexmanta View Post
Yeah, if it is pure white what's causing the problem, what happens if you level it down one single value so it becomes pure almost-white?
If I level it down or I change the color It works, I wrote that thing in the first post
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Old 01-29-2010, 06:26 AM
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Re: Apply Image and WTF?!

Here we go with the screenshot (8bit).
Is really strange, now in 16bit works :S
Attached Images
File Type: jpg applyimage.jpg (34.1 KB, 94 views)
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  #9  
Old 01-29-2010, 06:38 AM
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Re: Apply Image and WTF?!

Very interesting. I love it when people find stuff like this about the way photoshop does math.
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Old 01-29-2010, 07:15 AM
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Re: Apply Image and WTF?!

Quote:
Originally Posted by ApWizard View Post
the steps:
- make 2 copy;
- Blur the first one (in my case 50px radius);
- Apply Image on the second duplicate (Add - invert - scale: 2 - offset: 0) the first blurred one
ok.. those steps ONLY work on 16 bits 300 dpi ----it won't work with an 8 bit image

Quote:
Originally Posted by ApWizard View Post
Replacing this Add operation with a Subtract (changing the parameters to simulate an Add) works fine.
When u say: (changing the parameters to simulate an Add) --- you mean scale: 2 - offset: 128?

Because if so... That's the way it works with 8 bits at 300 dpi (and the ONLY WAY)


Call me stupid but I don't see your problem. The process depends entirely on the bits but you don't specify that in your OP
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