Applying LUTs and built-in looks in Video by Zaweba

A LUT, short for lookup table, is a file that maps every input colour to an output colour. Photographers, colourists and camera makers share them as an easy way to pass a look or a conversion from one program to another. Video by Zaweba reads them in two places, and it also ships twelve built-in looks for when you don't have a LUT to hand.

Two kinds of LUT and two slots

Not every LUT does the same job, and the app gives them separate slots.

The first slot applies a .cube LUT as part of the grade, with an intensity slider. This is for creative looks: a film emulation, a teal and orange treatment, a muted documentary style. The slider is important. Few looks are right at full strength on every shot, and pulling intensity back to half or less often gives a more natural result.

The second is an input LUT slot, which takes .cube or .3dl files and is applied before the grade. That is the place for technical LUTs, such as one a camera maker provides to turn its flat log picture into normal video. Putting it first means your corrections then work on a properly converted picture, which is what those conversion LUTs expect.

The twelve built-in looks

The built-in looks work like LUTs that come with the app, each with its own intensity. They are a quick way to try a direction for a project before committing. Apply one, play the cut through, and change your mind as often as you like. The intensity control means a look can be a subtle seasoning rather than the whole flavour.

A good order of work

Get the order right and LUTs behave well. If the footage is log, set the input LUT or the clip's input colour space first, so the picture looks like normal video. Then correct exposure and white balance with the colour controls. Only after that, add a creative LUT or a built-in look and set its intensity.

A creative LUT is built for a picture that already looks correct. Put it on badly exposed or off-balance footage and it exaggerates the problem. That is the reason so many looks seem great on one clip and awful on the next.

To give a whole scene the same look, put the LUT on an adjustment layer above the clips, rather than on each clip. One change then updates the whole stretch.

Making your own LUT from a grade

LUTs can also come out of Video by Zaweba. A grade can be exported as a 33-point .cube LUT, so a look you have built from curves, wheels and sliders can be reused in another project or handed to someone using different software. This pairs well with the built-in import: grade a hero shot carefully, export it, then bring it back as a LUT on other projects in the same series.

Mistakes with LUTs

Stacking several creative LUTs is the main one. Each bends colour in its own way and the result soon looks broken. Pick one and adjust around it.

Using a camera LUT on footage from a different camera is another. Log curves differ between makers, and a LUT designed for one gives odd colour on another. Video by Zaweba also lets you set the input colour space per clip for common camera log curves, which may be a simpler route than hunting for the right file.

Finally, judge with the scopes. A strong LUT can push blacks below the legal range or make skin go orange in a way your eyes get used to after a few minutes. The vectorscope's skin line is a reliable check.

LUTs are a shortcut, not a replacement for correction. In Video by Zaweba they are at their best as the last layer on footage you have already balanced.