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RP LIVE "Ask an Adobe Engineer" with Chris Cox

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  #21  
Old 01-30-2010, 05:34 PM
doctorontop doctorontop is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Thanks to Chris and Doug I really enjoyed the show

The drop white action would be very useful .........

Last edited by doctorontop; 01-30-2010 at 05:40 PM.
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  #22  
Old 01-30-2010, 07:54 PM
Chris Cox Chris Cox is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

And here is the "White To Transparency" action.
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  #23  
Old 01-30-2010, 08:01 PM
Chris Cox Chris Cox is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

bakerser - nothing brilliant there. USM and Highpass are related. Highpass does the difference between original image and GBlurred image and adds 128 (or 16384 in 16 bit) and that's it. USM skips the offset, and adds a fraction of the result back to the original image (if we ignore the threshold setting).
Using HighPass for sharpening can get more or less contrast than USM, depending on the blend mode used. That's because you're not just adding the difference but multiplying, screening, etc.
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  #24  
Old 01-30-2010, 08:13 PM
bakerser bakerser is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Quote:
Originally Posted by Chris Cox View Post
bakerser - nothing brilliant there. USM and Highpass are related. Highpass does the difference between original image and GBlurred image and adds 128 (or 16384 in 16 bit) and that's it. USM skips the offset, and adds a fraction of the result back to the original image (if we ignore the threshold setting).
Using HighPass for sharpening can get more or less contrast than USM, depending on the blend mode used. That's because you're not just adding the difference but multiplying, screening, etc.
First, thanks for the response.

Second, because it is directly calculating the difference, HP as implemented suffers from clipping when the difference between the original and GB version is >0.5 (say a series of hard lines). I've tried for some time to reconcile why that would have been coded (vs. halving the difference, which would reproduce the original image when blended in LL [losing one level to rounding]) and was wondering if there was a scientific reason for this, or if it simply wasn't expected that most would go HP'ing past a few pixels when it was coded?

Edit: Third: Thanks for sharing the action!
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  #25  
Old 01-30-2010, 11:47 PM
Chris Cox Chris Cox is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Easy: HighPass wasn't planned as a way to sharpen, it was just a high pass filter. Even the blend modes to use it for sharpening weren't invented at the time HighPass was written (Photoshop 1 or 2, can't recall right now).
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  #26  
Old 01-31-2010, 06:01 AM
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TriniK TriniK is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Thank you Chris for giving me some insight into the whole "crashing" issue that is the bane of my Photoshop life. (Frankly sometimes I wonder if I have another life...) I imagine that one has to be able to look under the bonnet at the engine which we as laymen are not able to and therefore blame it all on Adobe. '

There will still be a gnashing of teeth as I don't see the problem going away, but at least now I will be more understanding and good to know that the reports are monitored as I was sure they were just being sent into some alternate reality out there.
Thank you.
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  #27  
Old 01-31-2010, 08:25 AM
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mistermonday mistermonday is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Chris, welcome to RP. I am really sorry I was not able to make the Saturday time slot.
It is wonderful for all of the retouchers and Photoshopaholics hear to have a direct ear into Adobe for new features that will make us all more effective in our work / play and help make PS even more successful than it is.
As for the High Pass filter, I remember it from PS2. Everyone seems to have adopted the filter as the new "in" way of sharpening. However, everyone seems to have ignored the much maligned Unsharp Mask Filter, having been in PS for about as long. It turns out that an "Apply Image" High Pass will produce exactly the same result as the Unsharp Mask Filter with the same Radius setting and the Amount = 100 and Threshold = 0. Except with the USM, you can adjust the sharpness (edge contrast) with the Amount slider as well as adjust the Threshold. So with HP you go through a lot more work to achieve the same, or inferior results.
Anyway, I hope you will come back for another session with RP very soon. And of course if you are ever looking for feedback or beta testers, I am sure you would find a lot of cooperative and eager people here.
Congratulations on the milestone of the 20th anniversary of Photoshop and best wishes on the launch of CS5.
Regards, Murray
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  #28  
Old 01-31-2010, 12:47 PM
bakerser bakerser is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Quote:
Originally Posted by mistermonday View Post
However, everyone seems to have ignored the much maligned Unsharp Mask Filter, having been in PS for about as long. It turns out that an "Apply Image" High Pass will produce exactly the same result as the Unsharp Mask Filter with the same Radius setting and the Amount = 100 and Threshold = 0. Except with the USM, you can adjust the sharpness (edge contrast) with the Amount slider as well as adjust the Threshold. So with HP you go through a lot more work to achieve the same, or inferior results.
I would argue that by default, the HP filter returns a decidedly inferior result, clipping any differences > 0.5 to 0 or 1 as appropriate and losing the resulting detail. Some cling to it for workflow reasons (sharpening, skin work, smoothing wrinkles, etc), and of course there is the "Dave Hill = High Pass" contingent which will always survive on it. Interestingly, the Legacy B/C adjustment is a surefire solution (-50 contrast) for still using the HP filter in a workflow without suffering the clipping - not sure if that's of interest around these parts, though.
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  #29  
Old 01-31-2010, 01:24 PM
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Just as an aside, and I know that this is not a Photoshop forum so shall post it on one, but during the webinar when I expressed the dislike of the default "tab" opening, Chris said to got to preferences and just uncheck the "open in tabs" box. I did not say anything at the time, but I had already done this before and Photoshop just decided to ignore my request. Well after the webinar I tried it again, and in spite of relaunching Photoshop etc., and the box is clearly unchecked, the documents are still opening in tabs. Let me rephrase that. If I open a document (file >open) then fine - it floats, but if I drag a file from my desktop to the PS interface it jumps right to the tab position and then everything else disappears and I have to go to the icon or to Window >float all in windows, to get my already opened files/images back. That is the part that is driving me a little nuts. Chris if you are still viewing these postings and have any advice or feedback on this I would be eternally in your debt.
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  #30  
Old 01-31-2010, 06:26 PM
Chris Cox Chris Cox is offline
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Re: RP LIVE "Ask an Adobe Engineer" with Chris Cox

Hmm, I've never seen the preference fail EXCEPT when you try to open more than 100 documents (we eventually run out of resources to keep opening system windows and fall back on tabs to keep the number of windows in check).
That limit is lower if you have OpenGL enabled (it uses more resources). But I think it's still around 50 windows or higher.

If that isn't the case, and the preference is turned off -- then I'm not sure why it would still open documents in tabs. I made sure we had the preference because I LOATHE documents in tabs. And on Mac and Windows, I haven't had it fail to work as expected.
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