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Clarity simulation in Photoshop?

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  #11  
Old 03-03-2013, 08:23 PM
cardmaverick cardmaverick is offline
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Re: Clarity simulation in Photoshop?

Clarity is a a "localized contrast" technique, it's not just restricted to the mid-tones. You can get this effect if you use any HDR software program, but to a more destructive degree if you really want to push it hard. I do NOT recommend using ACR clarity, you are better off doing something manual in photoshop so you can prevent the formation of ugly halos. The two ways you can go about doing it are:

Doge / Burning with the use of blend if functions to only apply the dodge / burn to the details you want to enhance.

"Frequency Separation" - just youtube it, tons of videos on it. Once you get you're high detail layer, discard the other low frequency layer and blend the high frequency layer using something like hard light blending mode, enable a mask, erase the areas where halos are forming. I highly suggest you use something like surface blur when generating the high frequency layer, DO NOT use gaussian blurring - that will cause tons of halos to form.
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  #12  
Old 03-04-2013, 01:36 AM
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Re: Clarity simulation in Photoshop?

I don't know how you manage to get 'ugly halos' from ACR. I can't seem to get them - even pushed to 100%. have to say, I still feel this whole thing is slightly perverse. ACR Clarity, and 3rd Party software like Topaz Detail, is specifically designed to allow you to achieve this sort of effect with ease and precision. So why not use the tools for the job? If the OPs intention in setting himself this exercise is to develop a better understanding of how Photoshop works, I think there are many more productive approaches. Photoshop can be fun to learn, but try not to seek difficulties in learning it - they will present themselves in abundance.
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  #13  
Old 03-04-2013, 11:00 AM
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Re: Clarity simulation in Photoshop?

Quote:
Originally Posted by cardmaverick View Post
Clarity is a a "localized contrast" technique, it's not just restricted to the mid-tones.
I'm now not sure what to make of this but I suspect you're correct depending on image content. What do we make of this test I did using a step wedge where I set LR to minus 100, plus 100 and then zero clarity? Visually there's a difference to a small degree, the numbers (using a 3x3 sampling in Photoshop) show tiny differences numerically. I see the same effect with color gradients.

While Clarity was originally intended to produce a similar visual effect that Mac wrote, something else is going on. Mac's technique is targeting midtones if you use his suggestion for Blend If (that's where one decides what tones to affect). In LR, I'm not sure what's going on. Need to ping George Jardine about this and see what he thinks. He loves to dig deep into Lrs/ACR's processing.
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  #14  
Old 03-04-2013, 01:56 PM
cardmaverick cardmaverick is offline
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Re: Clarity simulation in Photoshop?

Great little post there Andrew - you can clearly see the halo effect I was talking about on the edges of each wedge. This effect gets worse when you start using other contrast tools on the image. These sorts of byproducts are why I prefer to do more manual localized contrast adjustments in photoshop.
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  #15  
Old 03-04-2013, 02:37 PM
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Re: Clarity simulation in Photoshop?

I would hardly call what you are observing in a tiny jpeg 'ugly halos'. The principle of local contrast is to emphasise the juxtaposition of light and dark, which is what it is doing, and what it is meant to do. You can't have your cake and eat it.
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  #16  
Old 03-04-2013, 02:52 PM
cardmaverick cardmaverick is offline
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Re: Clarity simulation in Photoshop?

If you use a dodge / burn tool you'll get a better result with a correct blend if setting. The problem with things like carity is that it creates that weird looking almost wave like appearance due to the gradients it produces on the chips in an attempt to separate them, especially at the edges. A manual doge will not have that effect, it's more like taking a pencil and coloring just the area you want to be darker darker, no need for having to ramp up the contrast in the areas adjacent to it then try to ramp it down, etc...
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  #17  
Old 03-04-2013, 03:07 PM
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Re: Clarity simulation in Photoshop?

So how long does it take you to achieve this effect over a whole image? Using the clarity slider takes a couple of seconds, and if indeed there were offensive halos, which I have never had a problem with, you could knock them out manually where they were obvious in a few strokes. Your method sounds like a solution looking for a problem.
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  #18  
Old 03-04-2013, 03:09 PM
redcrown redcrown is offline
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Re: Clarity simulation in Photoshop?

To understand "Clarity", and all it's contrast manipulation cousins, it's helpful to think like a computer programmer.

A programmer is given the task of writing code to change the value of a pixel from X to Y. What are the variables he has to work with?

In a simple case, there are only three variables.

1. The original value of the pixel. Specifically, where it falls in the total range of values. (0 to 255 in the 8 bit scale)
2. The direction of the change (plus or minus).
3. The magnitude of the desired change.

99% of Photoshop's adjustments use only these 3 variables. Curves, Levels, Hue/Sat, all the layer blend modes, etc. Take a simple S-Curve for example. If a pixel falls in the top half of the curve, the direction of change will be a plus. The magnitude will be the difference between the diagonal line and the appropriate point on the curve.

The ACR Clarity adjustment is in the other 1%. It uses a fourth variable, which is the value of "neighboring" pixels. Clarity has many sisters and cousins, most of which are outside of Photoshop. All HDR programs use the value of neighboring pixels. So do other plugins like Topaz Adjust and Topaz Detail. Each of these vary significantly in how many neighboring pixels they use, and how they treat the relation of those neighboring pixels to the "target" pixel.

Inside Photoshop (and ACR) there are only a few functions that use neighboring pixels in their calculations. In addition to Clarity, all the sharpening routines (USM) use neighboring pixels. The High Pass filter does, plus a few other lesser known filters like Minimum and Maximum.

Most of these functions give you some control of the variables. In USM for example, control over the number of neighboring pixels to evaluate is called "radius". Control over the relation between the target pixel and its neighbors is called "Threshold". In HDR programs and other plugins, these controls go by all kinds of different names.

The ACR Clarity adjustment gives no control over how to use neighboring pixels. It only has one slider for "magnitude". I can't find any documentation on what's really going on inside the ACR Clarity adjustment. It's likely proprietary, and understandably so, since there is a lot of competition in this area. But one thing I'm sure of - it's a very complicated and sophisticated formula. And a very good one too.

A lot of people guess that it's just a "midtone contrast" adjustment. It does not take much testing to see that it's much more than that. It adjusts all tones, yet does protect shadows and highlights. But it will leave some midtones completely unadjusted, IF those midtones fall within a broad area of similar tones. If fact, it will leave any tone pixel alone if that pixel is surrounded by a large number of similar neighbors.

In the example of Andrew's step wedge, that's why measuring in the middle of the wedges shows so little change. There are a lot of identical neighbors. Move toward the edges of the wedges and the change increases. Make the wedges much narrower and the changes increase more. For a better test, use a blank white image and create 3 narrow wedges. Fill one wedge with 20% gray, one with 50% gray, and one with 80% gray. Place them far apart so they are surrounded by a large area of white neighbors. Run this through ACR with a Clarity of 50 and see what happens. Then try to get the same effect with other adjustments, like the High Pass/Overlay technique.

I can find no other technique inside Photoshop that equals the ACR clarity slider. Some come close, but not close enough to replace or improve upon Clarity. The closest I can come is with the USM high radius low amount (Hiraloam) approach. While USM Hiraloam is close in concept, it is weak in results. One trick to try is to run USM Hiraloam at moderate amounts (20/150) but do it multiple times. Using USM Hiraloam multiple times at moderate settings seems to better than just once at aggressive settings.
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  #19  
Old 03-04-2013, 03:27 PM
cardmaverick cardmaverick is offline
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Re: Clarity simulation in Photoshop?

Quote:
Originally Posted by AKMac View Post
So how long does it take you to achieve this effect over a whole image? Using the clarity slider takes a couple of seconds, and if indeed there were offensive halos, which I have never had a problem with, you could knock them out manually where they were obvious in a few strokes. Your method sounds like a solution looking for a problem.
It depends on how much of the effect you want. It's not a "solution looking for a problem" - it's standard technique in high end retouching to use doge / burn layers coupled with blend if settings. You can't really control things like the ACR clarity slider in the same way you can control manual doging and burning. Some areas will need more intensity than others etc... If you don't like doing this, then don't do it. Guys like myself prefer a greater degree of control over the contrast strength, where it's applied, etc..
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  #20  
Old 03-04-2013, 04:19 PM
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Re: Clarity simulation in Photoshop?

Quote:
Originally Posted by AKMac View Post
I don't know how you manage to get 'ugly halos' from ACR.
LOL, I'm still in cs5. I thought they fixed that in cs6.

Quote:
Originally Posted by AKMac View Post
have to say, I still feel this whole thing is slightly perverse. ACR Clarity, and 3rd Party software like Topaz Detail, is specifically designed to allow you to achieve this sort of effect with ease and precision. So why not use the tools for the job?
I think those of us who've been using PS for years can forget how huge the program really is and how daunting it can be. I've hidden about half of the menu items that I never use and it's still big. There are so many videos and so many ways to accomplish the same task it can be overwhelming and easy to get stuck on one thing. I still ask questions and I'd be willing to bet at least a few of them leave some people here scratching their heads as to why I'm asking.

Ultimately, I'd suggest LR to the OP. The clarity slider is there and I've found that for repair work and restoring old scans I use PS but the vast majority of my SOC stuff I never leave LR.
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