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Match levels

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  #11  
Old 01-16-2012, 09:39 AM
Eikon Eikon is offline
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Re: Match levels

the reason was experimentation and trying new methods and workflows. case closed if you want... if anyone else can offer up a method, theyr free to do so.
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  #12  
Old 01-16-2012, 11:56 AM
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John Wheeler John Wheeler is offline
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Re: Match levels

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Originally Posted by Eikon View Post
the reason was experimentation and trying new methods and workflows.
Bingo! That short statement said it all to me for what you are looking for. Not necessarily an exact bit for bit match yet something that is close to the same functionality yet still maintains some sort of slider control for adjustments as opposed to matching an exact EV change to be applied to a number of images.

I pulled out my black box reverse engineering tools and here is what I came up with to simulate the exposure slider in ACR from within Photoshop proper.

- Start with Original image
- Add Invert Adjustment Layer next layer up
- Add Levels Adjustment Layer next layer up
- Add another Invert Adjustment Layer next layer up

Use the gamma slider (middle slide) of Levels adjustment Layer. In this case to darken image similar to negative EV move the slider to the left. If you want to brighten image move the Levels gamma slider to the right.

For reference, a -1.0EV setting on the Exposure ACR setting is an almost identical match with the Levels Adjustment gamma setting of 1.98 (moved to the left). For a +1EV setting on the exposure ACR setting is very close to a Levels gamma setting between .65 and .7 (moved to the right). This brightness setting is not an exact match because the ACR exposure setting actually clips the highest brights where as it is a smooth transition with the Photoshop Levels gamma slider.

One may think that putting two Invert Adjustment Layers would not make a difference. That is not the case. The gamma slider has larger percentage changes in the lower part of the luminosity range than the higher part. Doing the inversion makes the gamma slider have a larger impact in the higher parts of luminosity just like the ACR exposure slider.

Let us know how this works for you (I too do some similar experimentation looking for alternate workflows)
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  #13  
Old 01-17-2012, 06:03 AM
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Tony W Tony W is offline
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Re: Match levels

John an interesting solution to aproximate ACR control and one that I have to say that I would never have considered. I suspect you like to 'tinker' and take things apart somewhat - so do I .

I had a quick play with it and can see how it works (I think ) but cannot see at this time what benefits this may offer over just using ACR. Can you see a scenario where this would offer any benefit or was this merely an excercise?
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  #14  
Old 01-17-2012, 07:48 AM
Eikon Eikon is offline
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Re: Match levels

john, thats great... arent we glad we didnt throw in the towel right away! while its not perfect, i think its a good approach and gives a pretty close match. on the picture i used, reds were still a bit more saturated with this method as opposed to the exposure in ACR, but nothing that couldnt be fixed with another color adjustment. it works well in reverse too, making the exposure brighter.

ill play around with this method and see if it gets me where i want to be. i appreciate the insight!

oh... care to offer any wisdom and maths on why this works different than straight up levels?
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  #15  
Old 01-17-2012, 11:31 AM
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John Wheeler John Wheeler is offline
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Re: Match levels

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Originally Posted by Tony W View Post
Can you see a scenario where this would offer any benefit or was this merely an excercise?
The exercise was to provide an answer for Eikon. I can imagine some uses yet the ACR exposure tool is best especially for Camera Raw in pulling out details at the high or low end. I asked Eikon what the need was for and he said sure I can tell you but I will have to kill you if I do (so I declined). So Tony, I bet Eikon would tell you if your really really want to know

I do a lot of black box under the hood evaluation of PS to both find out new workflows yet also to find out when PS tools are not good to use (if that is tinkering then I guess I do).

Quote:
Originally Posted by Eikon View Post
john, thats great...oh... care to offer any wisdom and maths on why this works different than straight up levels?
Your welcome Eikon. I came up with this not by equations yet by taking a look at the transfer curve for the ACR exposure tool. Here is link to an image of the regular gamma curve in Levels in Photoshop:
http://upload.wikimedia.org/wikipedia/commons/7/74/GammaFunctionGraph.svg

The ACR exposure transfer curve is apparently very close to a curve that would closely match if you flipped the X axis and the Y axis both between 0 and 1. Since doing an inversion in Photoshop is the same as Output = 1-Input you just invert the Input before going through the gamma equation (Input ^ gamma) and flipping the Y axis is just inverting the result of the Levels gamma output. The result of the Y axis flipping also inverts the direction of the control on the Levels gamma slider (what was making dark now makes light). Hard to explain in text yet I did this all visually without equations (though that could be done too). Hope that gives you a feel for the approach I took. Graphs just compute in my head - what can I say
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  #16  
Old 01-17-2012, 11:57 AM
Eikon Eikon is offline
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Re: Match levels

lol, you lost me at "the". as long as it works!
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  #17  
Old 01-17-2012, 12:08 PM
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Tony W Tony W is offline
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Talking Re: Match levels

Quote:
Originally Posted by John Wheeler View Post
The exercise was to provide an answer for Eikon. I can imagine some uses yet the ACR exposure tool is best especially for Camera Raw in pulling out details at the high or low end. I asked Eikon what the need was for and he said sure I can tell you but I will have to kill you if I do (so I declined). So Tony, I bet Eikon would tell you if your really really want to know

I do a lot of black box under the hood evaluation of PS to both find out new workflows yet also to find out when PS tools are not good to use (if that is tinkering then I guess I do)....
Thanks John as I suspected and tried to point out in earlier posts there is little point in trying to re invent the wheel, without at least good reason. There seems little point in asking any further questions due to the fact that previous questions have been totally ignored. This of course is the OP's perogative but comes across at best as bad manners.
Yes what you do is tinkering in my book (using this definition One who enjoys experimenting with and repairing machine parts) - and long may you tinker well

Last edited by Tony W; 01-17-2012 at 12:30 PM. Reason: added tinkering message
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  #18  
Old 01-17-2012, 12:36 PM
Eikon Eikon is offline
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Re: Match levels

tony, which of your questions did i not answer that you want cleared up.
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  #19  
Old 01-17-2012, 12:39 PM
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John Wheeler John Wheeler is offline
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Re: Match levels

Hi Tony
Base on Eikon's inputs I just saw him as a fellow tinkerer and that's what triggered me to offer another type of solution. Sometimes the intermediate steps are just part of the journey

Quote:
Originally Posted by Eikon View Post
the reason was experimentation and trying new methods and workflows....
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  #20  
Old 01-17-2012, 12:52 PM
tom60634 tom60634 is offline
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Re: Match levels

Load 2 files into Photoshop.

Then go to Image>Adjustments>MatchColor.

Choose 1 file as destination the other as source.

You then have a minimum of 4 adjustment levels to fine tune your result.

This is useful when,for instance, you want to match the colors found in a photo of an athletic match to the colors found in an outdoor recital, or if you want to match the colors taken with different cameras of the same event.
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