Using ImpulZ LUTs to grade HDSLR footage

EDIT: Video now in 1080P

I’ve been experimenting with using film stock emulation LUTs (look-up tables) with footage shot on my Panasonic G6.

The problem has been that many of the film stock LUTs that are available online or come bundled with software like DaVinci Resolve assume that you are shooting with a camera that has a 10, 12-bit or RAW colour space, or else a logarithmic (log) recording format.

Using these LUTs with the G6 footage was tough. The results would be very aggressive and pushed, over-saturated and contrasty to the point of solarisation. I tried various techniques for making the G6 emulate a logarithmic colour space: putting all the picture profile settings to -5, raising the gamma and lowering the contrast in post, as well as Juan Melara’s video-gamma-to-log LUT, which you apply before the film stock LUT. Although I had some success with this latter method (Juan does stress that it is experimental), it was still difficult to get consistent results.

Enter Vision Color’s ImpulZ LUTs. What interested me here was that as well as the RAW-shooting Black Magic cameras of this world, Vision Color also provide sets of LUTs specifically geared towards plain old 8-bit colour-space H.264 video. They support cameras with flat shooting profiles (ie the GH4’s Cinelike D), including 3rd party profiles (such as Similaar’s Flaat profiles for Nikon cameras).

Detail of Tetrachrome 400 frame

I was a little disappointed at first that they don’t directly support older Panasonic cameras, the GH3, G6 and so on, but actually ImpulZ’s generic Rec.709 profiles work really well with G6 footage. The problems I described above of trying to simulate a log colour-profile before you apply the LUT are absent with ImpulZ. You can painlessly incorporate the LUTs into your grade without having to worry about everything becoming blown and crushed.

Shooting tips

In my limited testing so far, the Rec.709 LUTs seem to work best with a relatively full gamut of colour. In other words, when shooting use as much of the camera’s 8-bit colour space as you can, don’t shoot -5 -5 -5 -5 super-flat. I’m still experimenting with the settings, but, depending on the conditions, I have sharpness, contrast, and noise reduction on -2, ie just turned down enough to get the dynamic range I need and minimise aliasing. I’d be really interested in hearing how other people get on this. GH4 users who don’t like the Cinelike D profile should definitely explore shooting with a natural profile and just using the generic Rec.709 LUTs.

Kodak Elite Chrome 200 detail

Using LUTs in Final Cut Pro X

So far I’ve just done relatively simple grades with the LUTs. To use LUTs in Final Cut Pro X you’ll need LUT Utility.1 If a clip definitely needs a colour “correction”, if the white balance or exposure is way off for example, I do that before I apply the LUT. In Final Cut Pro X you can’t put a colour-board correction before an effect. Here’s how to get round this:

  1. Use the colour board to correct the clip

  2. Nest the clip(s) in question inside a compound clip (keyboard shortcut: Alt-G). EDIT: On the EOSHD forum, sudopera came up with a better idea: instead of a compound clip, use an adjustment layer, such as the one provided by Ripple Training. The advantage of this method is that as you’re doing your pre-LUT correction, in the Viewer you can see what the result will look like post-LUT. With compound clips on the other hand, the Viewer only shows the results of that layer, and you have to exit the clip to see the finished result.

  3. Apply LUT Utility to the compound clip (or the adjustment layer). The colour correction you did in step 1 is applied before the LUT

  4. You can do a post-LUT secondary correction if you wish, by using the colour board in the compound clip (or the adjustment layer).

For some shots however, the LUT brings out a colour response that wouldn’t otherwise be possible.

Of course this isn’t as flexible as DaVinci Resolve’s “node” system, but it does allow you to build up more complex grades. An alternative to this compound-clip-nesting technique is to use a third-party colour correction tool (or one you’ve made yourself in Motion 5) which sits in the Effects slot. That way you can put the colour correction before the LUT Utility effect.

The only issue I’ve run into is the “color implosion” LUT makes FCPX crash. I guess it really  does implode. Vision Color support have been really responsive. They haven’t been able to reproduce the crash so it could be something very specific to my set-up.

Walking Home

What I find particularly interesting is that rather than the very full-on, “pushed” look that we might associate with LUT-grades, some of the ImpulZ LUTs can have very subtle effects, depending on what you present them with. They are definitely designed to be used as part of a grade, not a substitute for one.

This means that rather than going all-out for the “film look”, a device which can become a visual cliche, a range of hybrid looks is possible, not-film and not-video.

The video above was shot on my way home from the barber, in “the blue hour”. Rather than compare the ImpulZ LUTs to out-of-camera footage, I thought a more interesting comparison would be to show the shot first with an ImpulZ LUT applied, and then with a regular colour-board grade. I did the colour-board grades first, ie without reference to the LUT. They are not an attempt to match the LUT-grades. They just show two directions each shot could be taken in, and are a work-in-progress. Some of the shots I think I prefer the LUT-less version. For some shots however, the LUT brings out a colour response that wouldn’t otherwise be possible. It’s another brush in the box. have a discount code that works until the 15th June.

Frank Glencairn has a really interesting post on his DaVinci workflow with Vision Color’s other LUT collection, Osiris

Music: Bee’s Lullaby from Amostra III

I have no affiliation with anyone mentioned in this post.

  1. If you want to use the LUTs in FCPX and Motion 5, you’ll need LUT Utility, which is available as a bundle with ImpulZ 

5 thoughts on “Using ImpulZ LUTs to grade HDSLR footage

  1. This was very helpful. I’ve been having a hard time getting any LUT to not look ridiculous on G6 footage.

    1. I’m glad this was useful for you. Also, if you haven’t seen this, have a look at Seb Castilho’s blog post here:

      He’s designed it for the GX7, and I haven’t had time to test it on the G6 yet, but the colour rendition of the two cameras is probably reasonably similar. One possible way of using the LUT that he discusses is as a pre-LUT, before adding a film-simulation on top.

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