Inverting Tones in a B and W image

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Marpel
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What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Inverting Tones in a B and W image

Post by Marpel » January 1st, 2018, 10:04 pm

Is there a way to invert the tones of a black and white image (similar to inverting a mask) without first converting it into an 8 bit black and white (mask) image.

I am primarily concerned about the degradation in quality in tones by going into 8 bit B and W and back again (as opposed to just 16 bit B and W to 48 bit colour).

I am experimenting on Color > Negative on some black and white images and wish to invert the tones on some without having to, first, convert to an 8 bit B and W mask, invert the tones, then convert to 48 bit colour (because, of course, Color > Negative only works on colour images).

Thanks,

Marv

jsachs
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Re: Inverting Tones in a B and W image

Post by jsachs » January 1st, 2018, 10:38 pm

Transformation/Gray/Negative
Jonathan Sachs
Digital Light & Color

MarkT
Posts: 195
Joined: April 24th, 2009, 2:07 pm

Re: Inverting Tones in a B and W image

Post by MarkT » January 1st, 2018, 11:16 pm

In version PWP 64 v7.0.20, I see Transformation/Gray/Negative. Is there a reason why masks won't work with this transformation?

Dieter Mayr
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Re: Inverting Tones in a B and W image

Post by Dieter Mayr » January 2nd, 2018, 2:57 am

Marv,

You can always convert a 16 bit Black and white image to a 48 bit colour image without degredation of quality.
The colour image just takes 3 times the space im memory, in a 16 bit BW image every pixel is represented as just one value, in a 48 bit image with 3 identical values for R, G and B.
I always use 48 bit colour for BW images, basically there is no other way to print them in a colour managed workflow in PWP as PWP does not support BW icc profiles.
Form your last post I suppose you want to use a mask when performing the transformation for inverting the tones?
There are many ways, you can use the Color/Negative transformation after converting to 48 bit colour as described above and use Color/Negative, or you can use Brighness Curve, a linear curve from 0/100 to 100/0 will invert the tones as well, and you can use a mask. And there are probably other ways I did not think of right now.
I suppose Grey/Negative was primarily designed to convert scanned BW negatives, so it would not be neccesary to include a mask, on the other had there is a mask available in Color/Negative. Probably Grey/Negative has no mask ability because it does not have a Transformation window to make any settings, and as there are other ways to achieve the goal Jonathan didn't bother to include a extra window just for a mask.
Dieter Mayr

Marpel
Posts: 320
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Inverting Tones in a B and W image

Post by Marpel » January 2nd, 2018, 9:04 pm

Jonathan,

Thanks for the info. Didn't even know Grey had a Negative as well.

Dieter,

Actually, I wasn't using a mask (at least as a mask) when inverting the tones. But, as I did not realize that there was Grey > Negative to invert, I was converting an image to 8 bit so I could then invert it (as when inverting a mask). I then converted the inverted image back to 48 bit colour. Now that I know there is Grey > Negative, I can just invert a 48 bit black and white image straight across. What I have been playing with is doing a diptych where one side is a positive image (after doing Color > Negative of the black and white - with some slider movements, the result can be a pleasing sepia-like image) while the other side is the reversed tone (sepia) image. To accomplish that, one image has to be the inverse of the other.

Marv

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