How LUTs work

How LUTs work in photo-editing

LUTs (lookup tables) are colour adjustment profiles used widely in cinematography and video editing to give movies their characteristic ‘look’. Their potential for stills photography is just as strong, as it’s like being able to use different films for different subjects and treatments. They are really taking off right now as more and more photo editing applications add direct support for LUTs.

How LUTs work
LUTs are technically similar to colour correction profiles, but work the opposite way – they’re designed for deliberate colour shifts and creative effects. Image by cocoparisienne from Pixabay

LUTs aren’t like regular adjustments. You can apply other adjustments on top of the LUT, but the LUT itself has no adjustments parameters in itself. LUTs apply a set of complex colour and tonal shifts set by the LUT creator, though some programs which support LUTs will let allow you to adjust the strength or intensity.

It sounds limiting, but actually it’s no different to choosing a different film-simulation profile in-camera, or selecting a different profile in Adobe Camera Raw or Lightroom.

LUTs versus presets: which is best?

That’s a good questions, especially since LUTs will often be used with software that already has image adjustment presets and effects, and LUTs might appear to do exactly the same job but with less control.

How LUTs work
LUTs can be used to give your photos instant ‘looks’ without any adjustments (left) that are consistent across different programs. Regular presets (right) may offer more control but they are software-specific and may combine complex adjustments. Image by Daniela Jakob from Pixabay

It’s true there is some crossover, but the two can work very effectively side by side and you can choose between them according to what you want to do. You can treat LUTs as an additional alternative to regular image adjustments in your software.

LUTs are useful in a number of specific circumstances:

1) They can give you the ‘look’ you want straight away without the need to carry out further adjustments.

2) If you do need to modify the image after applying a LUT, you’ll be starting with your software’s tools set to their baseline level and offering maximum editing flexibility. Regular presets software presets use the software’s adjustments to create the effect, so when you use a preset you may not have so much headroom for further adjustments – and it can sometimes be difficult to work out what you need to tweak to move the image in the direction you want.

3) LUTs are perfect for favourite ‘looks’ you want to use across a range of different programs. I use LUTs from Lutify.me, which I can apply in Alien Skin Exposure X, Lightroom, Capture One, Luminar or ON1 Photo RAW, knowing that I will get the same ‘look’ each time.

LUT technicalities

Most LUTs are ‘3D LUTs’, which means that they apply colour and tonal shifts in a 3D space, and have the .cube. format.

(At the time of writing, Capture One and Lightroom are a special case, requiring LUTs to be adapted as profiles these programs can use. Their support for LUTs is less direct, then, though third-party LUT developer Lutify.me does supply adapted LUT packs for these programs and there are technical workarounds for those who want to make the conversion themselves.)

How to use LUTs
Lightroom and Adobe Camera Raw use Profiles rather than LUTs, though it is possible to adapt LUTs into Profiles, and some vendors offer Lightroom-ready Profile versions alongside regular LUTs.

Even though 3D LUTs share the same format, they be adapted for different colour spaces. Those designed for cinematography may be offered as ‘Log LUTs’ which are designed to correct the extremely flat-looking high dynamic ‘log’ footage captured by professional video video cameras. These are not suitable for still photos, which don’t use a corresponding colour space. Instead, look for LUTs designed for the Rec 709 colour space. This is the video equivalent of the sRGB colour space, and will usually give the correct results.

Where LUTs have been designed specifically for stills, you’re unlikely to get this confusion.

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