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Can't D&B technique be greately simplified with...

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  #31  
Old 02-22-2010, 11:12 PM
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Re: Can't D&B technique be greately simplified wit

Correction: Please replace the "Curve" Tool with "Levels" Tool in this text. Sometimes I am so stoopid.

Hi again! (sorry huge post)

Some progress in my research regarding the mask generation for D&B.

A. The High Pass Filter

As already mentioned, I'd like to use the Photoshop integrated "High Pass" filter for generating the masks for the dodge and burn technique. This is for several reasons.

1. It seems to be a simple but still very flexible (and at all: super fast) option.
2. It delivers exactly what we need. A kind of contrast analysis result based on the source image
3. The filter is integrated in Photoshop already and has good visual control over the strength of the effect.
4. The resulting image is already basicly a greyscale which is very useful for further editing and modifying.

Now at first, we have to ask ourselves, what to f**k is a High Pass Filter?
It is with simple words a kind of bump map, which traces down the brightness differences (or contrast information) of an image to a certain adjustable amount.
I personally think, that is in fact "band passing" the image and not exactly "high passing" because highpassing would only cover the lights, like highpassing a sound would leave us with the highest frequencies, right? Whatsoever, it very much seems to filter out all the colors of our image, leaving us with the more or less intense pure contrasts of that image.

However, there are left some color information in that generated high pass filter result, especially as more you shift the amount to higher levels. I'll discuss this later. Unfortunately there is no "live effect" for this filter, so we have to copy our source and apply this effect filter to the copy. Doing that, gives us great visual response, seeing the result as a preview in real time, which is fantastic.

Note: Maybe there is someone, who can teach us the theory behind that high pass filtering. I do not want to pump up this thread unnecessarily with science. *smile*

Now we have to remove the colour information on that generated image. This is, because I currently do not know how much this information affects the results or even possibly distorts our entire process afterwards.
We simply do it with complete desaturating, to transform it into a "greyscale" image. Although there may be better choices (i.e. removing the color information with other tools completely from the bump map instead of simply converting it to gray, because it finally could skew up our results somehow... But I think the small amount of color information is ignorable for now.


B. Generating D&B Masks

Now, how can we generate useful masks from this generated bump map image?

As everybody knows, masks in Photoshop and most other pixel based graphic tools are simply black images with more or less unmasked areas with color or greyscale information to pass thru certain information. We want to achieve exactly that with our high pass image.

The high pass picture is now unfortunately a grey image with the middle tone R:128, G:128 and B:128. But this on the other side is great, because we can use simple byte shifting to transform our source into a mask. This means in fact 2 masks, one for the "lights" and one for the "shadows".

So how can we do that?
It's all about the "center point" here. This is also the reason why we have to do it twice (duplicating our source bump map). The number 128 is the magical key. It stands for the absolute middle tone in our image, the "zero point". The byte values for RGB are all at 128.

My suggestion is to simply use good old "Curves" tool to shift this "center point" up or down exactly what? Right 128 bytes for each kind of mask. This means we use one of our bump maps and shift the white (right) slider directly under the histogram in the curves panel for the RGB channel exactly 128 points/values to the left, so that it is placed in the exact center. This is finally the "shadows" mask.

But wait! Our image becomes white and not black. What's wrong?
Well we have to invert the result with another live filter so that we actually really have a mask for our shadows now.

Note: We are using real-time effects for that to being able to do any modifications afterwards to our masks.

We do the same vice versa with the other bump map copy number 2. This time we move the black slider under the histograph to the centre, exactly 128 bytes. We do not have to invert that image. It is now our "lights" mask.


C. Conclusion

We can use these masks, which now exactly cover our contrast information of the source image for further experiments. One for the lights and one for the shadows. Using it for Dodging and Burning or other blending.

Please note, that the intensity and the information of contrast is adjusted by adjusting the high pass filter in step A. already. The more details we want to cover the more we have to increase the value slider of the high pass effect which is used as the source image. Although the contrast of the resulting mask easily can be adjusted with the curves panel afterwards (which is only recommended for experts knowing what they are doing). If we made a wrong decision with the amount of high pass filtering we probably will get trouble later ...

PS: I've bounced down some images to demonstrate all that. But at first I need permission of the originator to use his image.

Correction: Please replace the "Curve" Tool with "Levels" Tool in this text. Sometimes I am so stoopid.

.

Last edited by _jason_; 02-23-2010 at 01:35 AM. Reason: correction
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  #32  
Old 02-22-2010, 11:22 PM
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Re: Can't D&B technique be greately simplified wit

Quote:
Originally Posted by holgaman View Post
Jason,
... A professional level retouch requires many artistic choices (based on personal preferences, which are as numerous as there are retouch artists), including, but not limited to, the dodging and burning process. You just can't teach a computer do that. ...
There is much truth in there...
I know, I tend to be more a technician sometimes...

But think of this:

Had you ever believed, that someone developes a tool, which corrects the singing voice (right tones) of a human without even recognizing it? Well such a tool already exists!!! It's Autotune from ANTARES, a genial development company. Even if each singer is an unque artist in his own unique expression and timbre, this tool actually revolutioniced the entire music production scene. Today no voice recording (even live on stage) is done without it anymore.

Our concern can be seen similar.
And please do not underrate artificial intelligence. Thats actually the future. *smile*

PS: No, I really do not want to go that far. I am merely interested in discovering some little theory behind all that to eventually have some useful experiences and solutions for certain tasks. At the moment that D&B technique BASICLY seems to be traceble down to really simple things. Of course I do not want to "replace" humans and artistic expressions ...

.

Last edited by _jason_; 02-22-2010 at 11:35 PM. Reason: spelling, additions
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  #33  
Old 02-22-2010, 11:47 PM
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Re: Can't D&B technique be greately simplified wit

That's really freaky about the Autotune, never heard of that. Hope I didn't sound like I thought your idea was bad, didn't mean to. I know from my own experience that after doing a bunch of dodging and burning and thinking I did a pretty good job, that I step back and the person looks like crap. Lots to learn. If there were a way to come up an automated system as you suggest and then be able to apply it selectively (maybe just a layer mask), it just might be the best of both worlds. Good luck.
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  #34  
Old 02-23-2010, 12:03 AM
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Re: Can't D&B technique be greately simplified wit

Well that AutoTune can be used in a way that everybody actually is hearing the effect! Do you remeber Chers "Do You Believe" Smash Hit? That actually was such a case of "creative overuse". *lol*

PS: Yes of course as a mask and always selectively!
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Old 02-23-2010, 12:11 AM
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Re: Can't D&B technique be greately simplified wit

No, I do not want to develop a new tool or program with the name "ProfessionalRetouch V1.0 - Get You Pictures Retouched in 1 Minute!"

Last edited by _jason_; 02-23-2010 at 12:12 AM. Reason: spelling
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  #36  
Old 02-23-2010, 01:00 AM
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Re: Can't D&B technique be greately simplified wit

Here are the promised images for the mask generation topic. (original image by courtesy of Cuervo79, thanks again)

The second is the high pass picture in greyscale, third the resulting "shadows" mask and fourth the "lights" mask.

As you actually can see, this all is quite subtle but can be intensified up to a certain amount.
Especially because of the byte shift, the "contrast space" on these masks is now merely the half, so that it easily could be intensified about 50 percent (but usually not more for some reasons).

And it is clearly obvious, that you can't apply it directly to the image because the eye and the lashes actually would be affected by any transformation too...

Well, next step actually would be to discover something that actually performs the required actions on the desired skin areas of our original image...

(Sorry being that technical here now.)

.
Attached Images
File Type: jpg 01.jpg (85.9 KB, 54 views)
File Type: jpg 02.jpg (85.1 KB, 44 views)
File Type: jpg 03.jpg (89.6 KB, 46 views)
File Type: jpg 04.jpg (88.0 KB, 46 views)

Last edited by _jason_; 02-23-2010 at 01:13 AM. Reason: addition
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  #37  
Old 02-23-2010, 01:24 AM
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Re: Can't D&B technique be greately simplified wit

Correction: Please replace the "Curve" Tool with "Levels" Tool in this text. Sometimes I am so stoopid.

Sorry, there is a logical error in the remark about the contrast space above. Using the "Curves" panel in the way we did, already scaled our values for the contrast. So there is probably no need to intensify the effect.

Remains to say, that these masks HAVE TO be placed pixel exact to the original source image to do their job. Any modification of the source image afterwards affects the precision drastically and invalidates our generated masks, of course.

Last edited by _jason_; 02-23-2010 at 01:36 AM. Reason: correction
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Old 02-23-2010, 03:10 AM
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Re: Can't D&B technique be greately simplified wit

HOT TIP:

A note to the high pass filter. This still remains a secret weapon for edge preserving sharpening and bluring. I'ts even better and gives more control than the "Unsharp Mask" tool, preferred by most professionals. You won't believe what amount of high quality sharpening / bluring is possible with proper usage of that technique.

If someone is interested, here is a file mapped to experimemt with the technique:
http://test.dizainer.net/HighPass.psd

It's simply making a copy of the image and placing it above the original, then transform the high pass filter with the right amount of details on it. Switch Blending mode to "Overlay" or any of the "Lights" in this group of blending modes an adjust opacity of the blending layer. Inverting the HP image will switch between bluring and sharpening.
Also try to adjusting lightness on the high pass filter image!

Btw., the file for generating the D&B Masks from the posts above is here:
http://test.dizainer.net/D&BMasks.psd

.

Last edited by _jason_; 02-23-2010 at 03:14 AM. Reason: correction
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Old 02-23-2010, 07:37 AM
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Re: Can't D&B technique be greately simplified wit

Hm !?
Applied a special softening anti wrinkle cream...
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Old 02-23-2010, 09:14 AM
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Re: Can't D&B technique be greately simplified wit

Jason,
It is important to get the facts correct and not circulate false information, so I will address a couple of concepts and will do them in reverse order than was posted.

Quote:
A note to the high pass filter. This still remains a secret weapon for edge preserving sharpening and bluring. I'ts even better and gives more control than the "Unsharp Mask" tool, preferred by most professionals.
Misconception 1 is that HP filter is better or more powerful than Unsharp Mask. An "accurate" (accurate to be defined later) HP filter done at any Radius R will produce the exact same results as a USM filter whose settings are Radius = R (same as HP), Amount = 100, and Threshold = 0. However with USM you have a huge lattitude in the controls Threshold and the Amount which controls the amount of contrast / sharpening. With HP, you have no threshold control and your only options for controlling contrast are applying curves or contrast blend modes.

Now at first, we have to ask ourselves, what to f**k is a High Pass Filter?
It is with simple words a kind of bump map, which traces down the brightness differences (or contrast information) of an image to a certain adjustable amount.
I personally think, that is in fact "band passing" the image and not exactly "high passing" because highpassing would only cover the lights, like highpassing a sound would leave us with the highest frequencies, right? Whatsoever, it very much seems to filter out all the colors of our image, leaving us with the more or less intense pure contrasts of that image.

Quote:
However, there are left some color information in that generated high pass filter result, especially as more you shift the amount to higher levels. I'll discuss this later. Unfortunately there is no "live effect" for this filter, so we have to copy our source and apply this effect filter to the copy. Doing that, gives us great visual response, seeing the result as a preview in real time, which is fantastic.
Misconception 2: HP is not a Bump Map and it does not filter color. For illustration purposed I have attached a very small zipped psd file.
The High Pass filter looks for edges -all edges and only edges - whose radii are equal to or less than the width specified by your radius selection. After isolating those edges, the filter increases the contrast between the colors on both sides of the edge. All other edges of the image higher than the chosen radius are reduced to mid gray 128.
A Gaussian Blur filter is the opposite of HP in that it selects all edges whose Radius is lower than the chosen R value and it reduces the contrast (which is same as blurring) of the colors along the edge and it does nothing to the edges whose radii are higher than the chosen R value.
I won't go into the messy math but if you take any image and perform an "accurate" HP and a GB at the same radius and you mathematically add the HP + GB you will get the exact same image as you started with i.o.w HP + GB = Original Image.
The attached psd file will demonstrate that. Turn on only the BG. Now turn on the GB layer (btw, the R=10 for this demo). You see where the image is blurred along the center line. Run your mouse across slowly and watch how the color values change as you move from very right to very left. Now turn off the GB layer and check the numbers on the BG.
Next turn on the BG and the HP layer. See the increase in contrast and see what has happened to the color values. Also noticed the effect on the BG is that it has been sharpened, But that is what sharpening is - just an increase in edge contrast. For ease of demonstartion, only one channel has been used for each color Left Swatch = 0,120, 0; Right Swatch = 170, 0, 0.

You will notice that the HP layer is set to Linear Light blend mode at 50% OP. The reason is that Photoshop does not have a "Add" blend mode, except when using the Calculations or Apply Image commands. However, it turns out that Linear Light at 50% opacity is mathematically equal to the add function.

Finally, turn on all layers aaand alternately Alt+Click the eye icon on the BG layer to toggle it on and off. You will see that the view of the BG is exacly identical to the view of the GB and HP layers turned on. HP+GB= BG (orig)

Now above I mentioned an "accurate" HP. The math behind HP and GB is messy and there are round off error in the many calculations that underly it. So if you use the Filter > Other > High Pass method of generating the HP layer and add it to GB ot will look very close to the orig but not be perfect. If you want another way to make a very accurate high pass so that your eye will not be able to see any difference, there is a long thread at the modelmayhem forum fo reading in your spare time. The link is here:
http://www.modelmayhem.com/po.php?th...=439098&page=1

Finally, if you are interested the 2nd attachment is Cuervo79's final D&B - the slow and accurate way.

Regards, Murray
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File Type: jpg Cuervo79 Final Retouch.jpg (77.3 KB, 63 views)
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File Type: zip Jason GB+HP-MM.zip (6.5 KB, 12 views)
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