BMPC4K – Vertical Patches/Lines at ISO400 Sensor Problem

Hi everyone,

I’m encountering a strange issue on my Pocket Cinema Camera 4K that wasn’t present before and has now started showing consistently: at ISO 400, particularly in underexposed scenes with lateral contrasty lighting, the sensor appears to generate vertical “lighter” patches or lines in the image.

These artefacts seem not to be banding or FPN in the traditional sense — they appear more like vertical veils or zones that catch and amplify side light with a clear edge, regardless of what lens is on. I shoot BRAW 3:1 Constant Bitrate.
They’re most evident when a bright light source (like the computer monitor in the tests, but the real-world scenario is in illuminated city night exterior where I want to keep ISO400: these patches/lines appear on the black sky) is positioned to the left or right of frame in an otherwise dark environment.

I’ve performed a range of controlled tests and I’m attaching screenshots [with exacerbated grading to better identify the line/patch) from DaVinci Resolve, Gallery grabs, and the original BRAW files for download through a SwissTransfer Link — so you can judge directly.

- Resolve GUI Screenshots:
1-1-1: Screen Light On – Room Light Off
1-2-1: Screen Light Off – Room Light Off
1-3-1: Screen Light Off – Room Light On
1-4-1: Screen Light On – Room Light On
1-5-1: Screen Light On – Room Light Off
1-5-2: Screen Light On – Room Light Off (just before turning the room light on)
1-5-3: Screen Light On – Room Light On
1-14-1: Lens Cap On (to test for sensor-level pattern)

- Gallery Still Exports (grabbed from above):
Still 2025-06-21 222858_1.1.1
Still 2025-06-21 222858_1.2.1
Still 2025-06-21 222858_1.3.1
Still 2025-06-21 222858_1.4.1
Still 2025-06-21 222858_1.5.1
Still 2025-06-21 222858_1.5.2
Still 2025-06-21 222858_1.5.3
Still 2025-06-21 222858_1.14.1

SwissTransfer Link:
https://www.swisstransfer.com/d/5e57dbc ... a57ac592d1

Embed for reference:

1-1-1 - Screen Light On - Room Light Off.png (924.93 KiB) Viewed 280 times

What I’m asking:

- Have you noticed this behavior on your Pocket 4K in similar conditions (ISO 400, underexposed scene, strong side lighting)?

- Does this appear on your camera as well, or could this indicate an early-stage sensor degradation?

- Would anyone be kind enough to replicate the test by shooting at ISO 400 in film dynamic range, with a bright white computer screen or any light source on one side of frame and a black/dark screen on the other? If the patches appear for others too, that would help immensely in assessing whether this is systemic or unit-specific.

Thank you everyone in advance

That's nothing to worry about, no signs of sensor degradation. It is expected behavior for this sensor in such light conditions. This has been already discussed here on this forum, but many years ago - about when the camera was quite new.

I am downloading your footage now and have a look, but I guess there won't be any surprises for me.