I have been reading the ACR and Lightroom Profile SDK and tried producing a profile that would invert an image using a Look Table. It seemed to me to be quite simple, but it didn't work.
My logic was that the HSV look table should be easy to produce inverted colour: if the hue <= 180 then add 180, otherwise subtract 180. Leave the saturation and value unchanged. I decided the look table only needed two entries, so my csv file contained:
2, 1, 1, 0
180, 1, 1
-180, 1, 1
This didn't seem to do anything. Reading a bit more from the dng spec 1.4.0.0 suggested that each hue value should have at least two saturation values, so I changed the csv file to:
2, 2, 1, 0
180, 1, 1
180, 1, 1
-180, 1, 1
-180, 1, 1
This at least made a visual change to the image when applied as a profile, but nothing like a negative of the image. Adding another hue division:
3, 2, 1, 0
180, 1, 1
180, 1, 1
180, 1, 1
-180, 1, 1
-180, 1, 1
-180, 1, 1
changed the image a bit more. Then trying four hue divisions changes the image again, but adding more hue and/or saturation divisions resulted in no further changes to the image's appearance when applied as a profile. I created another profile with a reversed point curve to visualise what I was actually trying to achieve.
These are the preset previews for profiles I created using ACR (Invert LT21 - Look Table 2 hues, 1 saturation, Invert LT22 - Look Table 2 hues, 2 saturations, etc) All have a single value division. The last one, Invert PC is the point curve inversion (a proper negative).
Anyone got any clues as to where I'm going wrong in my thinking or have I totally missed the mark somewhere?
My logic was that the HSV look table should be easy to produce inverted colour: if the hue <= 180 then add 180, otherwise subtract 180. Leave the saturation and value unchanged. I decided the look table only needed two entries, so my csv file contained:
2, 1, 1, 0
180, 1, 1
-180, 1, 1
This didn't seem to do anything. Reading a bit more from the dng spec 1.4.0.0 suggested that each hue value should have at least two saturation values, so I changed the csv file to:
2, 2, 1, 0
180, 1, 1
180, 1, 1
-180, 1, 1
-180, 1, 1
This at least made a visual change to the image when applied as a profile, but nothing like a negative of the image. Adding another hue division:
3, 2, 1, 0
180, 1, 1
180, 1, 1
180, 1, 1
-180, 1, 1
-180, 1, 1
-180, 1, 1
changed the image a bit more. Then trying four hue divisions changes the image again, but adding more hue and/or saturation divisions resulted in no further changes to the image's appearance when applied as a profile. I created another profile with a reversed point curve to visualise what I was actually trying to achieve.
These are the preset previews for profiles I created using ACR (Invert LT21 - Look Table 2 hues, 1 saturation, Invert LT22 - Look Table 2 hues, 2 saturations, etc) All have a single value division. The last one, Invert PC is the point curve inversion (a proper negative).
Anyone got any clues as to where I'm going wrong in my thinking or have I totally missed the mark somewhere?
Posted 4 months ago
John R. Ellis, Champion
Thanks John,
I have used the process outlined here https://www.iamthejeff.com/post/32/the-best-way-to-color-correct-c-41-negative-film-scans and find it very good. So getting a good result in Photoshop is quite easy. I have used this procedure in Photoshop to create a LUT and then a Camera Raw profile for a few different negative colour film types. The results in Lightroom are reasonable, but with Lr develop adjustments working on the negative, the tone adjustments are reversed and many others cannot be used because they produce wild colour shifts, such as vibrance and saturation. The white balance and auto tone tools are useless too. A bit of manual adjustment of WB works. Here is an example of a DSLR 'scanned' film negative with one of my profiles applied.
And after a bit of adjusting
It would be so much better to have a tool or tool set that could do these steps natively in Lr so that all the develop tools can be used normally on a raw image.
A negative tool has been asked for by users for 7 years now and it is so disappointing that Adobe hasn't even given those users the courtesy of responded to the requests. Not even to say 'No we will not be implementing a negative function'. Just nothing, completely ignored. Like myself, there are many photographers with considerable archives of film negatives who are experimenting with DSLR 'scanning' to digital raw and would dearly love to process them in Lr. It's hardly rocket science, with a good starting point being an invert option coupled with a remove film mask colour cast (not by changing white balance) so that all the Lr develop tools work as normal.
I have used the process outlined here https://www.iamthejeff.com/post/32/the-best-way-to-color-correct-c-41-negative-film-scans and find it very good. So getting a good result in Photoshop is quite easy. I have used this procedure in Photoshop to create a LUT and then a Camera Raw profile for a few different negative colour film types. The results in Lightroom are reasonable, but with Lr develop adjustments working on the negative, the tone adjustments are reversed and many others cannot be used because they produce wild colour shifts, such as vibrance and saturation. The white balance and auto tone tools are useless too. A bit of manual adjustment of WB works. Here is an example of a DSLR 'scanned' film negative with one of my profiles applied.
And after a bit of adjusting
It would be so much better to have a tool or tool set that could do these steps natively in Lr so that all the develop tools can be used normally on a raw image.
A negative tool has been asked for by users for 7 years now and it is so disappointing that Adobe hasn't even given those users the courtesy of responded to the requests. Not even to say 'No we will not be implementing a negative function'. Just nothing, completely ignored. Like myself, there are many photographers with considerable archives of film negatives who are experimenting with DSLR 'scanning' to digital raw and would dearly love to process them in Lr. It's hardly rocket science, with a good starting point being an invert option coupled with a remove film mask colour cast (not by changing white balance) so that all the Lr develop tools work as normal.
John R. Ellis, Champion
Merging a copy with the relevant topic.
Please reference the new conversation here: Camera Raw/Lightroom: Creating profiles using a Look Table (merging)
Please reference the new conversation here: Camera Raw/Lightroom: Creating profiles using a Look Table (merging)
Anthony Blackett
Cameron Rad
john beardsworth
Cameron Rad
john beardsworth
Victoria Bampton - Lightroom Queen, Champion