Hey gang,
So I've been working on making the Pocket 4K work as an easy and simple to use (especially in post color grading) B-Cam to the Alexa. Having owned and shot on an Alexa for the last couple of years I have come to love how reliable and straightforward grading the Alexa footage is. Shoot it in Log C, toss the Arri Log C to Rec 709 LUT and then sweeten the grade to taste/style. Because of how watertight the Log C to Rec 709 workflow is on Alexa footage most of my grades for the Alexa aren't terribly deep. I don't need to jump through hoops just to get a balanced, normal, pleasing neutral starting point. Now if I'm going for a *very* specific look or style of course the nodes pile up, but all of that is downstream of a rock solid, easy neutral grade I get with the Alexa. So I wanted that same simple workflow with my new Pocket 4k. I like how flexible BRAW is, but the default factory look of the Pocket 4k is a bit punchier than the Alexa. The Pocket 4k's default look is not ugly by any stretch, but it's certainly distinct, which makes it hard to mix the two in the same edit. So I've cooked up a LUT that gets me most of the way there. It's not perfect, but I think the results pass the "squint test", which is good enough to intercut the footage without any major bumps. Let's have a look from the top...

The footage straight out of each camera, plus a white balance and exposure adjustment. Same lens (Zeiss ZF.2 50mm cinevised). Pocket 4k using a Speedbooster while the Alexa is equipped with an aftermarket Nikon lens mount.
The difference in sensor sizes, gamut outputs, and Speedbooster influence pretty much precludes a *perfect* exposure match in camera. So the goal was to get close enough, which we could do quite easily. The lighting set up for this test lies comfortably within the dynamic range of the Alexa, while it's probably pushing the outer limits of the Pocket 4k.
The Pocket 4K footage has noticeable magenta cast out of the camera, where the Alexa has its signature green cast. As noted above, both of these clips have had their tint corrected. Overall the Pocket 4k Film log is contrastier and more saturated than Arri Log C.

Applying the "usual" color space & gamut LUT to each footage to get them into Rec709 gamut/color space. The Pocket 4k is using the built in "BlackMagic Pocket 4k Film to Extended Video 4" LUT that comes with DaVinci Resolve. The Alexa using the industry standard "Arri LogC to Rec709" LUT.
Pocket footage looks nice in its own way, but it doesn't cut well with Alexa footage. Some quick exposure, contrast, and saturation adjustments would help, but the way the two cameras handle color would still be fundamentally problematic.

If we take it one step further and add the same Rec709 based Film Convert look FX to each of the Rec709 corrected clips, we see the Pocket 4k footage and Alexa footage get a little closer in vibe, but the original issues in the color space correcting BM LUT work are still present, as they always would be. It's axiomatic in color grading that issues earlier in the node stream still exist downstream.
At this stage throwing a look FX or LUT onto it isn't going to fix the fundamental differences in the camera's footage.

So here we see what it looks like using my own custom LUT to make the Pocket 4k footage look more like Alexa footage that has the Arri LogC to Rec709 LUT applied.
And no, it's not a *perfect* match. To get an absolutely perfect match requires a level of experience and skill which sadly outstrips my own at the moment.
But my goal is to get *close enough* that I can treat both cameras pretty much the same in my grading work flow.
In that respect, I think I've found some measure of success.
There are still differences, so in some scenes I will likely employ some minor tweaks down stream to adjust where the LUT cannot 100% accurately hit the mark. But we're talking a single node here or there to tweak, not an entire new parallel tree. As a time saving device I think the custom LUT does the job.

Just for giggles I threw a Rec709 based Film Convert FX node onto both clips. Again, not perfect, but the typical audience member could watch these cameras intercut and not get bumped out of the experience.

So at this point I am comfortable shooting on both the Blackmagic Pocket 4k and Arri Alexa on the same project and in a couple of quick nodes get them looking *pretty much* the same. In the quick turn around world of indy film or second tier commercial post-production I'm thinking this is a win.

And if budget or physical constraints keep me from shooting with the Arri Alexa, this LUT allows me to use my Pocket 4k as the primary camera while still getting a look that is, while not perfect, a workably close approximation of the Alexa (minus whatever physical restraints the BMPCC4k sensor introduces). It's silly to promise that a Pocket 4k can deliver 100% of what the Alexa can and I'm not delusional enough to attempt to, but I was pleasantly surprised that I could get this close. BM really do have themselves a robust little camera with the Pocket 4k.