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Polarization Filter?


Ninanoki

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one company sells such polarization filter for dentistry to better see colors. what adjustments should i play with to achieve similar result? to better see dentin/enamel difference (dentin is yellow ; enamel is blue)11159901_858926400865263_2756262331601995341_o.jpg
 

dv8_fx

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Hi there.... there was a past discussion about dentistry and Photoshop somewhere around here.... Unless someone among us finds it, do a search for it as well..
 

Ninanoki

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no, it is a completely different question. we were talking about color matching. now i'm looking for a way to differ yellow color from blue .
 

dv8_fx

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one company sells such polarization filter for dentistry to better see colors. what adjustments should i play with to achieve similar result? to better see dentin/enamel difference (dentin is yellow ; enamel is blue)View attachment 61037


I found it..... but ooooops.... also found out you posted it and was entirely different as it touched on "tooth color analysis" ..... :cheesygrin:.
 

thebestcpu

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Hi Ninanoki

It is apparent that the product information you shared uses both polarized light and a polarized filter to eliminate reflections and differentiate dentin and enamel. I am assuming that you want a similar result without using that product and also without using your own polarized lights and polarized filters (correct me if I am wrong).

If my assumptions are correct, just to be clear, one cannot duplicate the polarized light effect in PS with standard lighting. The almost exact parallel to is to try and differentiate color in a B&W image. The polarization information in light is not captured in a standard image and therefore is not there to be adjusted/manipulated to ones advantage.

So I will assume that you want the ability to better differentiate colors in a standard image. If there is a hue or saturation difference between the dentin and enamel in a standard image then there might be a way to amplify that difference into a luminosity difference and give you something of interest. To have good differentiation though, from my experience it will be very important to have either a raw image or a 16 bit TIFF image to start from to see what can be done. This is because the hue and saturation differences are subtle and unfortunately, JPEG images compress the hue and saturation (actually posterizes those components) and the 8 bit depth make differentiation of small differences very hard or impossible.

If you could provide a high resolution raw image or 16 TIFF image of some example teeth then I think forum members could give it a real good shot to see what could be done. That would be my first suggestion.
 

thebestcpu

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Hi Ninanoki

Here is what can be done with your raw image.

All I did was bring it into PS in 16 bit and ProPhoto RGB
Convert to Lab mode
Then added a 50% gray level Layer above the original and set blend to Luminosity (this is to isolate the colors)
Then added a curves adjustment Layer and use the Auto function only on the "a" and "b" channels
Then added a posterization adjustment Layer and in this case set the levels to 5

This should give you a hue/sat colorized map of your image that is posterized to visually show you the different areas

Something similar can be done for luminosity by itself.

Now, this is not calibrated to anything so I am sure a lot more is involved. Is this anything along the lines of which you seek?

John Wheeler

Lab-posterized-color.jpg

Use a curves adjustment Layer and used the auto button on the a and b channels
 

Ninanoki

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thanks John, it works, I was able to create such action and got the same result but how do you make a 50 % gray layer?

i also wonder which method is better. i can also trace an image in adobe illustrator and depending on number of colors i get such results:
toothd4.jpgtoothd10.jpgtoothd50.jpg
 

thebestcpu

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Hi Ninanoki

You make a 50% gray level by first creating a blank Layer and then using Edit > Fill > 50% Gray with normal blend and 100% opacity options

To be honest, what you have created does not look similar to my image. Yet I am glad you feel you are on your way to something you need.

For your reference, here is a link to the Layered TIFF file for the image I created so you can see the details of the process I used: https://www.dropbox.com/s/00rloc18hk2araa/tooth copy.tif?dl=0

Hope that is of some help.

John Wheeler
 

Ninanoki

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Dear John
i've already bought polarization filter. i will post results here today or tomorrow, but please tell me should i use this filter with our without ring flash?

i was using ring flash to see more details of the tooth structure.
 

thebestcpu

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Dear John
i've already bought polarization filter. i will post results here today or tomorrow, but please tell me should i use this filter with our without ring flash?

I am no expert on polarized light or appropriate filters. However, the basics are that if you have some elements of light that are polarized (such as possible from reflections), you can adjust the filter to reduce/eliminate that particular reflection. Light from most sources is not polarized yet can become polarized through a variety of process (reflection is just one).

Sometimes it is just experimentation on how the filter is adjusted. Here is a link that will explain the basics: http://www.physicsclassroom.com/class/light/Lesson-1/Polarization
 

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