Blackmagic Forum

Here's a throwback to the early days of the BMPC 4K rollout.

I recently purchased a used BMPC 4K to act as a second camera for my other BMPC 4K. Unfortunately, this newly acquired camera has serious sensor banding issues that haven't been fixed by upgrading the firmware. After talking to various repair shops, I've concluded the sensor is a lost cause. My only option is to use the camera sparingly and for b-roll that isn't crucial.

So here's what I'm asking folks who know more about Resolve than me: since the banding is consistent, is there a method to limit or mitigate the banding to salvage some footage? Standard noise reduction helps a little but the lines are still visible. Of course, I'd also welcome any hardware fix recommendations.

I've attached a frame from the camera with the lens cap on and the offset cranked up to 55 to show the banding, as well as a frame that has high, mid and shadow to demonstrate how the banding affects footage. Both are taken at 400 ISO, RAW, film, 180 degrees. Straight from camera, ACES color management.




Black frame hi res: https://www.dropbox.com/s/eycvuun8dbx2dmg/1.11.1_1.11.1.tif?dl=0
Sample frame hi res: https://www.dropbox.com/s/mxcoll37wj09gow/1.10.1_1.10.1.tif?dl=0

Link does not open on my phone

Neither on my desktop.

waltervolpatto wrote:Link does not open on my phone

Okay try it now

are you under exposing?

I will try to scale with the softer scale available plus blur the blue channel two pixels and the R and G only one. Then add back a bit of resolve grain.

I could get rid of most of the streaks by re-adjusting the individual RGB levels of your black clip and subtracting (layer blend mode set to subtract) it from the live clip in After Effects. Should be the same in Resolve.

I would shoot a few seconds of black, temporal denoise it and use that footage for subtraction.
You will have to do that for each ISO step (or you will have to adjust your black frames for the ISO steps).
And for all different resolutions.

waltervolpatto wrote:are you under exposing?

I will try to scale with the softer scale available plus blur the blue channel two pixels and the R and G only one. Then add back a bit of resolve grain.

I'm not underexposing. The lines are there at all times and exposures.

ETA: I have three BMPC 4Ks. This is the only one that has green vertical bands with the lens cap on.

Robert Niessner wrote:I could get rid of most of the streaks by re-adjusting the individual RGB levels of your black clip and subtracting (layer blend mode set to subtract) it from the live clip in After Effects. Should be the same in Resolve.

I would shoot a few seconds of black, temporal denoise it and use that footage for subtraction.
You will have to do that for each ISO step (or you will have to adjust your black frames for the ISO steps).
And for all different resolutions.

Thanks I’ll give this a try. I’ve never shot at anything other than the native 400 ISO with these cameras so that helps.