Obviously, there are no rules dictating what one has to do with regard to prepping a film scan prior to color conversion with NLP, but a question arises: If a scan of a color negative was already generated with gamma 2.2 by the scanning software, would the TIF Scan Prep utility make any observable difference to the color conversion done by Negative Lab Pro?
My understanding is that the TIF Scan Prep utility essentially does the following:
Takes the original TIF file and temporarily converts it to gamma 1.0 (regardless of the file’s original gamma);
Applies color multipliers to the gamma 1.0 color space; and finally
Converts the file to gamma 2.2 (this is the form of the TIF file that is then worked on by NLP).
The intention of the utility seems to be to expand the tonality of the original file before it gets worked on by NLP. In practice, this expansion of tonality should be observable in an expansion of the histogram of the image after the TIF Scan Prep utility has been used. But, if the original scan was already generated with gamma 2.2 by the scanning software, should the “deconversion” to gamma 1.0 followed by “reconversion” back to gamma 2.2 have any practical effect?
Yes, this what the Tiff Scan Prep utility currently does.
Yes, it will make a difference because of step #2. The color multipliers are more accurately applied when in gamma 1.0 - because in gamma 2.2 the gamma curve will impact each color channel slightly differently because each color channel will be in a slightly different place along the curve. Will it make a big difference? Not necessarily. But it should be slightly more accurate.
With all that said, though, the biggest difference of using the Tiff Prep Utility will definitely be when working with a gamma 1.0 file because the expansion of tonality on the original Tiff helps with accuracy once you begin converting and editing in NLP.
I continue to experiment with alternatives to the Tiff Prep Utility because of the time & storage the extra step consumes.
Oh no…did a 40 negative serie with NikonScan gamma 2.2 in TIF but did not apply the prep utility. Can i still go back to the original positive scan?
Update:
Tried with Unconvert, apply prep utility and NLP again, but result is more yellow. Also got an extra gamma 1.0 file(?)…am i suppose to do something with that file?
Lucky i got an unprocessed backup of the file on another drive, applied the prep util, white balance it and crop it, apply NLP… result is still little yellowish.
I liked the straight conversion from NikonScan gamma 2.2 though.
But it is not! Tiff scan prep actually converts to the gamma 1, not gamma 2.2!
In my case Tiff scan prep produces the files ending with “gamma-1”
And this is the files converted from my linear tiff files with further gamma expansion
in terms of imagemagick
+gamma .45455
then
-gamma 1
I’m not sure what you are trying to show exactly? The image produced by the Tiff Prep utility above looks correct. It has taken a linear image and applied a gamma correction of 2.2. It has also attempted to analyze the base color of the negative, and apply a color multiplier adjustment, although in this case that isn’t really necessary since it is black and white.
If you are using ImageMagic and want to adjust the gamma of a linear file to 2.2, you should be able to use the command “-gamma 2.2” instead of the multiple steps you have done. Just note that it won’t match exactly (especially color images) since Tiff Prep is also analyzing the film base color.
For software that produces non linear files (like flextight, which produces files with a gamma of 1.8), the TIFF prep utility will first convert the file to linear, then analyze the color of the film base and make adjustments in linear space, and then output the final to gamma 2.2. It’s just a bit more accurate this way.
