Photo courtesy of Spectracal
UPDATED: 7/27/2015 : Many EVF (electronic viewfinders) and on-camera monitors (such as those from Atomos and SmallHD) have built-in technology to allow the use of LUTs on-set. The use can range from simply providing a display LUT, so you can focus and expose properly while recording a log \ flat image, to actually burning in a creative look into the footage being recorded.
The word LUT may have lost all meaning to you, or it may mean numerous things, aside from it's actual definition of "Look Up Table". I'll try & explain it before we move forward, as it's important to realize how limited LUTs are. A LUT is nothing more than a massive set of pre-calculated numbers for both input and output colors, or a long list of "this green #1 turns to into green #2" style equations. I am simplifying this significantly, but I am trying to make a few points about LUTs in general before I go forward and abuse them for our creative intentions. You give a LUT a color and it mathematically hands back another color, no matter if it's applied to Canon DSLR, RED, Alexa, scanned film footage, etc. A LUT is a stupid mathematical conversion & has no idea what it's being applied to. They're created for ONE specific purpose, whether to emulate\prepare for a film print (sample LUTs, FilmConvert, Impulz), convert between a LOG format and Rec709 (HDTV) for a specific camera, or provide a creative look (OSIRIS, Blockbuster LUTS, ). Okay, long story short: LUTs are stupid math-based color conversions that don't know anything about what camera or format we're using, what color space we're in (LOG or REC709), how the footage was shot\lit\exposed yet many believe they are "magical one-step color correction" machines. Now that we know that's not so, how can we use them creatively while understanding their limitations?
Note: I wanted to mention FilmConvert at this point, as its essentially a on-the-fly LUT generator that's been programmed to adjust it's curve based on the input camera and the "output" film emulation (so actually 2 LUTs), but its still essentially a LUT for our purposes.
LOG OR NOT? - With YouTube, Vimeo, and forums galore spreading different information, this has become a very confusing subject. If your footage was shoot on a Canon or Nikon DSLR, even with a picture profile like Cinestyle, VisionTech, Prolost, or many of the others low contrast picture styles, I highly recommend you do not treat this as "LOG" and treat it as Rec709 footage when choosing "creative" LUTs that require a choice. That being said, if there happens to be a specific option for that profile\setting, proceed to use that one, of course. The exception to this is some of the newer cameras like the Sony A7s, which comes with proper S-Log2 can be treated as LOG. You can tell because the feature is ALWAYS inherited from the higher end models from that manufacturer.
One of the original "true" purposes of LUTs is to convert between video gamma formats, such as converting Canon C-Log, REDLogFilm, BMDFilm and LogC to Rec709 (HDTV standard). I've likely left out several LOG gamma types, but you get the point. Most camera manufacturers will provide a "normalization" LUT, or several in the case of Arri and Blackmagic, that allows a direct conversion of the image from the "milky", low contrast log footage captured in camera (which allows the camera to record the most image data) to a more "contrasty" and saturated Rec709 standard, WITHOUT any other changes. No creative additions are made by using these LUTs. These are very useful in establishing a good base image\set-up for grading a LOG footage, as you can simply focus on color having already converted the image from LOG gamma to Rec709.
If your are working with RED footage in REDLogFilm, Alexa footage in LogC, or any Blackmagic footage in BMDFilm, proceed to use LOG based LUTs for contrast expansion & the color effects in one step. If you'd like more control, you can use a technical LUT to convert your LOG footage to Rec709 and then use Rec709 "look" LUTs, as this will provide a more subtle look.
Here you can download a set of generic Rec709 to Log (technical) conversion LUTs, if you'd like to try working with your footage in true LOG but shot in standard Rec709 or if you're unable to shoot in LOG. Just be aware, 8 bit DSLR footage will not fair well with this harsh of a post correction. These conversions is best served for footage that is 10 bit or higher. Thanks to Juan Melara for the conversion LUTs and huge thanks to Stephanie Duchaine for being our model for these tests. We'll hopefully be seeing more of her in future content!
Creative Use of LUTS
Now that you hopefully understand LUTs and some of the different types and uses for them, we get to step into the fun and creative aspect of using LUTs: establishing looks. I'll state this first: I feel there are better alternative to "look" LUTs, such as powergrades, plug-ins, presets, and other more configurable methods of sharing color manipulation. However, seeing as they've become popular lately, I figured I'd like to share some creative uses and "misuses" of LUTs that I've found through my work. These strategies will work whether you are grading in an NLE like Adobe Premiere Pro of Final Cut X, compositors like After Effects, and of course, color correction applications like DaVinci Resolve and Adobe Speedgrade.
1. Set up LUTs on an adjustment layer in Premiere of After Effects, use a 3 node set-up in Resolve, or 3 layer set-up in SpeedGrade. This will allow you to separate. This allows you to make adjustments to the image using a basic three-way color corrector before the LUT and after, should you want to. They have very different effects, especially if you are working with LOG footage. Try to put any changes to exposure or color temperature before the LUT.
2. Convert an image from LOG to Rec709, and try using a Rec709 based "look" LUTs instead of the LOG version for a slightly less-intense effect. This also separates the normalization and "look" process that are combined in a "LOG" based look LUTs so you can reduce\intensify the "look" using opacity\transparency controls on the Rec709 "look" LUT layer or node. You do not have this extra control when using a single "LOG" based look LUT.
3. Combining "look" LUTs with FilmConvert can yield very unique and pleasing results when done subtly with taste. As I mentioned previously, Filmconvert is essentially an "on-the-fly" film stock emulation LUT generator in the form of a plug-in, and it certainly can be combined with some light "look" LUTs, and even some grading to make everything fall together . I would highly recommend using some of the less intense looks (aka avoid crazy cross processed or hard teal\orange looks), or bring down the opacity on a super intense look like M31 from the OSIRIS pack.
4. Treat your film as if it were shot on film by using actual film print stocks. Try and emulate a different "film stock\style" for creative purposes, using one stock for one location and one stock for another to give them distinct looks. You can use the film stock LUTs provided by Juan Melara, who has provided a Kodak and a Fuji stock for us to play with, or even several that are included with DaVinci Resolve Lite. Use the "ConstLclip" version of the LUTs. While these are "technical" LUTs created to show what the film will look like after it will be printed back to film for projection in a theater, we can leverage them for a slightly different purpose. In recent times, as the majority of film projection and capture has gone digital, colorists began to use these technical "monitoring" LUTs as look LUTs to add a unique look to the generic "hyper-clean" image captured by today's high-end digital cameras. We can do that exact same thing, but just be aware these type of emulations tend to have some degradation on the image quality.
5. If your grading application allows for it, such as Resolve and Speedgrade, selectively isolate everything but the shadows or the highlights of the image using a secondary selection, power window, qualifier, etc and apply a look LUT to only a selective portion of the image. This works if a LUT is causing noise to appear in a specific area of the images, such as the shadows or highlights. This can help intense looks, such as OSIRIS M31, fit in and look less "slapped on". The "chroma - light & dark" feature is Resolve is especially useful for this use.
6. If you understand what a LUT was created to be used on, what it's intended to do, and where it's limitation is, your limit is simply your imagination and your scopes. I mention your scopes as LUTs break 32 bit floating point build into Premiere, Resolve, After Effects and most NLE\Color applications. Long Story Short: If your have image data below 0 or above 100 on your scopes, you MUST correct it to be within 0 - 100 before applying a LUT. Otherwise, anything above 100 and below o will be "clipped" out, never to be found again.
I hope you enjoyed this whirlwind article about using LUTs creatively. I literally just scratched the surface, but I wanted to share some of the techniques I found useful and see what tricks you guys use with LUTS, both technically and creatively. Please leave a comment below if you found this useful or if you have a technique to share!
Here is an example that combines a technical LUT (for conversion), standard grading (power windows, curves, three-way CC wheels) and a creative look LUTs (all adjusted appropriately) for a very unique image:
Disclaimer: Although I do mention several specific packages in this article, I am not associated with any of them and I did not receive any compensation for their mention. I will only mention a tools if I personally find it useful in my work and I feel its worth sharing.