Didn’t want this issue to be buried in the various threads that discuss the 4.6K sensor. Just posted this to the official BMD forum:
I have created a four part series from the tests i did 2017-03-04 to examine the control of infrared contamination on the URSA Mini 4.6K PL camera using a variety of filters.
Parts 1 and 2 feature IRND filters. The question was raised about combining the Mini Pro filters with additional ND filters to see if the Mini Pro filters will suffice to control infrared. Part 2 may answer that question for you as I present the three scenarios.
Part 1 examines just the 7 NiSi Nano IRND filters which behave in the same manner as the 3 built-in IRND filters found in the URSA Mini Pro cameras.
Part 2 examines the use of the SLR Magic Image Enhancer, B+W 486 MRC IR Cut, and S:R Magic Vari-ND filters alone or in combination with the NiSi filters to approximate how those filters may perform with the built-in IRND filters on the URSA Mini Pro camera. I can’t be sure of course because i am not actually testing the Mini Pro.
No password required.
Please read the additional notes for each video. Hope you find these tests useful. I also have simply graded all these clips and the results indicate that all clips appear to be quite good matches once they are corrected in post. I may present the graded videos if you want to see those, when I can upload them, but next week I’ll upload Part 3 and Part 4 that are specific to the SLR Magic Image Enhancer and the SLR Magic Vari-ND.
Here is the Part 3 that isolates the SLR Magic Vari-ND II filter so you can judge its efficacy. It is not intended to affect infrared light, but you may see some changes in colour at the maximum setting. It is easily corrected in post.
Here is Part 4 with the NiSi Nano 1.8 first and then with the SLR Magic Image Enhancer added for a subtle improvement to infrared filtration. The SLR Magic Image Enhancer shapes visible light and near infrared and then cuts infrared beyond the ‘normal’ cutoff on most IR Cut filters. I also added a distortion test of the 85mm APO and it looks good as a closeup lens (focus was 9.5’).