How do you transfer sunglasses tint to a LUT

I

Imamacuser

Veteran
Hi everyone,

I have a pair of amber tinted sunglasses that I really like the look of, and would like to accurately transfer that tint to a LUT to apply to grass and foliage in color grading.

I could white balance to a gray card and take a second shot with the sunglasses in front of the camera's lens, but I'm not sure where to go from there. In software I can select the gray card with the eye dropper tool to correct the color, but is there a way to invert that correction and save it as a LUT? I have access to Photoshop CS 5.5, Affinity Photo, and the Lite version of Davinci Resolve.

Thanks
 
Shoot a chip chart with primaries and a greyscale with the glasses and without. In Resolve, match your clean shot to the filtered shot. That should get you at least part of the way there. Tweak on the curves until you get something satisfactory. Export your grade as a lut. You may need to develop a few different versions for various lighting conditions.

No idea if that will work well for you, but having a common reference to work from is the logical first step. The other obvious solution is to use a filter on your cam, even if it's just a second pair of your shades rigged in front of your lens (of course, if this isn't a paid project).
 
For effects like graduated tints of sunglasses or any other type of tint, design your colors, colorization, enhancement or filter look I use the Digital Film Tools DFX OFX plugin kit. Being OFX architecture it works in most NLE packages. Use it in Resolve all the time. Needs a reasonably decent system to run super smooth. Heavily GPU supported. Use one of the hundreds of presets or modify any of them to suit your requirements. Tints and grads fully configurable to taste. You also have emulations of nearly all the Tiffen grad filters, Pro Mists, Glimmer Glass, Pearlescent, Diffusion, etc, etc the list goes on. Nice that it works in 32-bit floating point so maintains the quality of your footage unless it's a lunatic grade. Not super cheap but I LUV this package!

Some of the filters you could us besides the 'optical' filters.

DFT is comprised of the following filters: Ambient Light, Black and White, Bleach Bypass, Blur, Borders, Cartoon, Center Spot, Chroma Bands, Chromatic Aberration, Color Correct, Color Gradient, Color Infrared, Colorize Gradient, Color Shadow, Color Spot, Cross Processing, Day for Night, DeBand, DeBlock, DeFog, DeFringe, DeNoise, Depth of Field, Detail, Develop, Diffusion, Dot, Double Fog, Dual Gradient, Enhancing, Eye Light, Fan Rays, Film Stocks, Flag, Flashing, Fluorescent, Fog, F-Stop, Frost, Gels, Glow, Glow Darks, Glow Edges, Grain, Grunge, Harris Shutter, Haze, High Contrast, Hot Spot, Ice Halos, Infrared, Kelvin, Key Light, Lens Distortion, Lens Flare, Light, Looks, Low Contrast, Match, Mist, Multi Star, ND Gradient, Net, Night Vision, Overexpose, Ozone, Pastel, Pencil, Photographic, Polarizer, Printer Points, Rack Focus, Radial Exposure, Radial Streaks, Radial Tint, Rainbow, Random Spikes, Rays, Reflector, ReLight, Selective Color Correct, Selective Saturation, Sepia, Shadows/Highlights, Skin Tone, Silk, Sky, Soft Light, Spikes, Spiral Rays, Split Field, Split Tone, Star, Streaks, Sunset, Telecine, Temperature, Texture, Three Strip, Tint, Tone Adjust, Two Strip, Vignette, Water Droplets, Wide Angle Lens, X-Ray and zMatte.

Chris Young

https://www.digitalfilmtools.com/dft/

It's no longer on YouTube but I downloaded a DFX webinar a couple of years back which if is anyone is interested it can be downloaded from here:

https://1drv.ms/u/s!AtImLuGZQ98YgRChtroNsSV77TiS?e=lF3eC9
 
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Here are the things I'm going to try based on your suggestions:

Use Resolve's Auto Shot Match feature to match the clean gray card to the one taken through the sunglasses, and save the correction as a LUT.

Manually adjust the clean shot of a gray card to match the RGB values of the shot taken through the sunglasses, and save the corrections as a LUT. I'm not sure how to approach this, should I try the offset color wheel or RGB mixer?

I found a post on Blackmagic's forum that suggested inverting a LUT in a program called Lattice, but more research is required.

Just to clarify, I want to apply the amber tint to a selective area, i.e. select the foliage with Resolve's HSL Qualifier and apply the tint only to the foliage.
 
My best recommendation is to follow Chris' advice above. Even if Digital Film Tools isn't the right solution for this project, there's a very good chance that someone, somewhere has emulated the gradient/tint that you want to match (or damn close to it!). It's worth some time investigating that, because really, reinventing the wheel is basically just hard and difficult work that usually yields little to zero reward for having done so.

If you really want to go the manual route, however, here's some considerations (in no particular order):

- You should not simply use an 18% grey card. You really do need multiple points of reference. Ideally, you would have a chip chart with greyscales AND primary targets... even if it's something like an X-rite Color Checker or a DSC Pocket Camette (my favorite: https://www.bhphotovideo.com/c/product/465713-REG/DSC_Labs_PCE_PCE_Pocket_Camette_Test.html). Either of these will give you several points for which to match. Worst case scenario (i.e. you don't have the budget for one of these charts), maybe put patches of black and white gaffers tape on your grey card... now suddenly, you've tripled the number of reference points (and since you're just matching looks, you don't need to worry about these targets representing specific vectors or lumas to be "in spec").

- I suggest to first find the most efficient (least destructive) way to push/pull your way to match those targets. It won't be easy, but you can probably get close.

- Next, use the curves (e.g. Sat vs. Hue, Sat vs. Sat, Luma vs. Sat, etc.) to eyeball the HSL for the hues in between your primary targets... do this second step, btw, by matching real-world shots (not the chip chart, because that won't give you anything but the targets to match).

- And, when you do shoot through the filter (sunglasses) remember that the lens will most likely have some curvature. When you shoot through curved filters, you get added density applied unevenly, which will throw everything out of whack in a hurry. So, to minimize this (likely not prevent, though), I would recommend using a long lens or zoom on the long end of the lens so that you are shooting through the smallest portion of the flattest part of the sunglasses. You might even go one step further and frame the targets on your chart to the middle third.

I love the adventure of bush-hacking, but be forewarned that this will probably not be a simple and straightforward process (I refer you again to Chris' suggestion above). I understand that you want to apply this look/effect only to foliage. I might suggest here also that before setting down this possibly treacherous path of matching the tint in you shades, that you check to see if you can get a good mask on said foliage. In my experience, it can be only a slight half-step above masking hair in terms of the level of difficulty (of course it depends on the shot and foliage, itself). You may want to pre-test applying some other effect on your foliage to see how much you can get away with before it starts to get too weird. For example, you might only get to about 40% opacity before all the imperfections of the mask start to become obvious. At least this will help inform you as to how perfect of a match you will need to make, and may save you a lot of headache by having your expectations already in place.

Best of luck to you, and please share how it all turned out in the end!
 
I don't have a color chart, I put that in the want category rather than need category. A DSC Labs Pocket OneShot is on my wish list, but I haven't been able to bring myself to spend that much money on something that will inevitably get lost or fade/wear out in short order. I do have a chart with gray, black, & white patches, so I'll give it a shot with that.

I'll use the longest lens I have, a 200mm.

This isn't for a paid project, just something I think would look cool and work in theory.

Thanks for the suggestions.
 
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