I have to say, I am extremely disappointed in this review.  As an avid reader/fan of NBC for 8 years, this is the most absolutely, positively *wrong* review I have ever read on your normally great tech publication.

It just so happens that I have purchased and have been testing 2 of these models for the past 3 weeks, same configuration as you have in this review and another, same configuration but FHD display, not 4k.

Without going line for line, let me tell you two aspects of your report - very important ones - that are exactly contrary to my own measurements, using the same benchmarks and similar measurement tools:

1) The screen on the 4k model is 340 nit at its brightest, and averages 320 nit.  It sounds to me like the tester did not defeat the "adaptive brightness" function of the screen, as such a different result was recorded.

2)...and far, far more important: the 4k unit could not provide 9 hours of battery life with wifi on and the screen at anything over 20 nit, and even then I don't think it would.  Just this week approximately 7 professional reviews of the 4k model have been published (we're talking the 13,3", not the 15.6" (which has a much larger battery) and on average they got between 5 and 6 hours battery life, which is exactly the range I achieved under several moderate use cases.  Just streaming a Netflix (not at 4k) the unit powered down 3 times at 5.8-6,2 hrs.  Plus, common sense will tell you that if the unit draws an average of 9-11 mw and has a 58 mwh battery, there's no way it will come close to 9 hrs.

My only criticism of NBC reviews is that when your tests produce results that are contrary to every other published review and rather defy common sense, you rarely appear to pull a review until you can be sure you receive a unit that is in proper working order.  As for your battery life tests, I can find no explanation for them except "operator error."  This (otherwise superb) 4k laptop could barely run for 6.5 hrs. with wifi disconnected, brightness at 120 nit and only one MS Office program running simple tasks, small files.  That's not bad for a machine this magnificent, but it begs the question, what business does a 58 mwh battery machine have in an i7U cpu/4k-320 nit screen ultrabook?  Well, it's fine if the user is going to stay by a plug most of the time or use an auxillary backup battery.  It was truly joyful to watch 4k programming on the 13" screen, but it seems a poor use of the outstanding "workhorse" computer this HP Spectre x360 is to match such a power-sucking screen with a battery wholly incapable of supporting it for a day's use.

I would like to use the .icm Profile (ICC File (X-Rite i1Pro 2)) from your calibration. Can someone tell me how I can assign that to my hd grafics card on my spectre? Trying to download that only leads to a html file, that is not recognized by my grafic card

Regarding the Display brightness: I already own that 4k 2017 Spectre above. I had the Lenovo 910 FHD in comparison, as well as the Spectre X360 late 2016 with FHD. They both where definitely less bright, and that was the reason I returned the Lenovo, and kept this one. Could it be that that one you testet had some issues with the Screen?