Re: Art Duplication [OT removing light fall off manually]
Re: Art Duplication [OT removing light fall off manually]
- Subject: Re: Art Duplication [OT removing light fall off manually]
- From: "Miles, Peter" <email@hidden>
- Date: Thu, 24 Sep 2015 07:20:07 +0000
- Thread-topic: Art Duplication [OT removing light fall off manually]
Apologies about being Off Topic
I made a mistake in my instructions for manually removing light falloff manually with photoshop.
This method of manual illumination evening works flawlessly, for the situations I have used it for so far*.
I have attached a screen grab of of an example to show the layer structure along with a before and after image.
https://dl.dropboxusercontent.com/u/41869696/Manual equalisation.jpg
(*flat art copy work and evening out coloured backlighting in microscope images.)
The idea behind the file structure.
the upper layer contains a record of light falloff, illumination issues across the field that I want to remove.
the lower layer is the target values I would like to achieve.
the difference mode for these two layers gives me the offset RGB values required to shift my non-uniform image pixel values to the ideal ones.
by using using “linear Dodge (add)" on the folder that contains both these two layers, I can add these offset values to any image.
to move this correction layer in pixel-register to images that have the same light fall off issues, I hold the shift Key as I drag and drop the correction folder on the other images.
Corrected instructions are
1- shoot a good illumination reference image to record light falloff, color shifts ect, spot it and blur it around 20~30 pixels
2 -use the clipping levels display to find the brightest pixels the image. Sample the color of the those pixels.
3- make a layer _BELOW_ this illumination reference image and flood that layer with the sampled color. (this is your target image)
3 - put the blend mode of the upper layer to difference.
4- put both these layers inside a folder
5 - change the folder blend mode of the folder to "linear dodge (add)"
6- Drag and drop this folder on images that were shot with the same light fall off. hold the shift key to drop in pixel register.
If you give it a go I’d be interested to hear if it works for your images
If it breaks for your images, let me know too.
Thanks and best regards
Peter
Note
In the screen grab, I wanted to show the effect on the image I was working on, but I the artists did not want me to show it.
So I have just applied the fix to the unspotted illumination reference.
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