Lightroom spectral values

  • Thread starter Thread starter Chris Brandin
  • Start date Start date
Status
Not open for further replies.
C

Chris Brandin

Guest
In case anybody wants to emulate film stocks or filters, etc... I've figured out approximate wavelength values for the color sliders in Lightroom. They are:

Red - 7''
Orange - 59'
Yellow - 578
Green - 56'
Aqua - 5''
Blue - 48'

Purple and Magenta, obviously, have no corresponding spectral values.

Chris
 
Sort by date Sort by votes
Interesting Chris. Many of the members here will have no idea what that's about (and I will admit I'm a little vague on the details myself! ;)), so would you like to illustrate how one would use those details. You've obviously been investigating carefully!
 
Upvote 0 Downvote
I'll admit it's a little geeky - sorry.

Films (especially B&W) get much of their "look" because of how they respond to different colors in the spectrum. Usually you can obtain a spectral response chart from film manufacturers that plots sensitivity against spectral wavelength. One of the reasons Tri-x looks different than Verichrome, for example, is because they each respond to different colors differently. Old films tended to be orthochromatic rather than panchromatic - which is why skin looks so light, and lips so dark on old Hollywood portraits. If you wanted to emulate a film's look you could do so by setting the grayscale mix sliders appropriately. You can do this fairly easily by getting a film's sensitivity chart and using it to determine which sliders to change and by how much.

Filters work much the same way.

Chris
 
Upvote 0 Downvote
Thanks for the techie clarification Chris. It's a been a lot of years since I last messed with film!
 
Upvote 0 Downvote
At first I didn't see the point in emulating film stock because the potential for color accuracy is so good with digital. Then I realized that films never were designed (for the most part) to achieve color accuracy - that would yield largely boring images. Film companies went for pleasant results rather than accurate ones; it's how they created competitive advantage. Fuji Velvia is a good example - people love the look, and it is anything but "correct".

Film companies spent fortunes fine-tuning the look of their films. It seems sensible to me to leverage all the research and creative effort they put into their film designs. Knowing your films might be a good idea, even in a strictly digital domain.

Chris
 
Upvote 0 Downvote
I've seen Thomas Knoll say (more than once) that photographers demand absolutely accurate color reproduction, and when they get it they hate it.

Hence, the FAQ here, "what happened to my pretty JPEG in LR?" Canon and Nikon (others?) know that accuracy won't sell as many cameras as well as fully (overly?) saturated "tropical vacation advertisements". Similar to your Velvia example.

The default Camera Profiles furnished with LR/CR are painstakingly accurate (under the specified lighting conditions). Yet, that's one of the most contentious points of LR discussion.
 
Upvote 0 Downvote
Yup, that's what we want. And we can get there more easily starting from the accurate color Adobe gives us than we could get accurate color starting from an unknown "pleasing color" calibration. Adobe definitely did the right thing!

Chris
 
Upvote 0 Downvote
Black & White Filter Presets Created for Lightroom

Chris, fantastic work! I realize these are estimates, but I took them and coupled them with light transmissions from Kodak Wratten filters and made some presets for the most common filters.

I quoted your work here in my blog article which is here: http://outdoorimages.blogspot.com/2''8/'5/lightroom-presets-available-black-white.html

I may work on some combined filters as well.

Thanks again!
 
Upvote 0 Downvote
Nice work Chris! Thank you for your troubles.

Ellis
 
Upvote 0 Downvote
It's nice to see somebody make use of this - and thanks for the nice credit on your blog.

I noticed something about the luminance sliders you might find interesting. There are two different ways to convert to B&W in Lightroom. One is to use the grayscale mode. The other is to stay in color mode and set all the saturation sliders to -1''. There are some significant differences between the two. The luminance sliders behave differently - in color mode they are more subtle and clipping is avoided. In grayscale mode the effect is more extreme and clipping can occur. Also, in color mode you can make very subtle changes in tonality by changing the hue sliders (they are not available in grayscale mode).

I've read in several places that many people prefer the color mode of B&W conversion over the grayscale mode. I prefer it as well - mainly because of the clipping issue.

Chris
 
Upvote 0 Downvote
I suppose I should explain why the spectral values I came up with are "approximate". The main reason is that the exact values change somewhat depending on where the images came from. I have a few different cameras and the exact values change slightly depending on which camera I use. The changes are small, however, and shouldn't make much perceptual difference. I assume this is because of differences in camera calibrations in ACR.

Chris
 
Upvote 0 Downvote
Chris,
with 1.4 Lightroom allowed you to use Colour Noise reduction with Grayscale, which effectively gives the same control as desaturating each of the sliders in HSL and using the Luminance sliders. The reason why Martin Evening came up with that method was because of colour based noise using Grayscale.
Hope this helps,
Sean.
 
Upvote 0 Downvote
Does that mean that it might offer better noise reduction too? I hadn't thought of that.

What I noticed about the sliders is that with grayscale mode if you set all the sliders at -1'', for example, all pure colors (i.e. colors that contain two or less color values - grey components are still gray) will come out black - all at '%; in color mode they don’t come out completely black, rather they are more in proportion with their original values, only compressed. For example, if you have a magenta value derived from R=128 + G=' + B=128 (in Photoshop) it will come out black ('%) if the luminance sliders are set to -1'' in grayscale mode; in color mode, they will come out at about 1'%. It looks to me like the color mode has a knee function at the extremes whereas grayscale mode clips at the extremes.

A color value that contains all three primaries, like R=128 + G=128 + B=128, interestingly (or oddly, perhaps), will stay at a mid-gray with both modes even if all sliders are set to -1''. It appears the sliders affect only spectral and synthetic colors and not natural grays. That means that if you try to stack virtual red, green, and blue filters in Lightroom the result will be different than it would be in the physical world. With real filters the result would be simply a darker image, with Lightroom the result is that colored components of the original image are darker but the components that started out as natural gray stay the same.

I just tried out another experiment. I created a spectrum with a neutral gray frame. Then I set all the luminance sliders to -1''. The spectrum came out very dark whereas the neutral gray frame stayed the same. This is true for all three modes - grayscale, color with saturations set to -1'', and color with the saturation values left at '. It seems to me that with all the luminance sliders set to -1'' the gray should have come out dark too.

From a theoretical standpoint this looks like a bug. It poses some very interesting possibilities, though. If Adobe corrects this, I hope they provide an option to leave it the way it is. I think I'll post this in the bug section as well.

Chris
 
Upvote 0 Downvote
Come to think of it - this isn't a bug, the sliders do what they are supposed to do for color work.:oops: They just can't be used to emulate B&W films and filters with complete accuracy.

Chris
 
Upvote 0 Downvote
Status
Not open for further replies.
Back
Top