IR Cut Filter corrosion - because it's not made of glass!!!

I noticed some spots on the footage of my BMPCC 4K, and thought it would be some dried-out rain droplets from my previous video shoot, as it started drizzling in the last few minutes - I imagined these could have gotten in through the cooling vents on the side of the lens mount.



After finding the spots on the IR Cut Filter I tried several times to clean these spots, using appropriate MFT swabs and sensor cleaning fluid. No luck. White vinegar, isopropyl alcohol, nothing worked. These spots remained in place, almost as if... they were on the inside? That would make sense, I thought, thinking of how the cooling vents would push air into the sensor, behind the IR Cut Filter.

So I did what any industrious DIY-inclined person would do and, similarly to a filter replacement procedure, removed this IR Cut Filter out of the camera to try to clean these damn spots, this time cleaning both sides of it.

No chance. You may already guess what these spots are: corrosion, right? Let's talk about the why, though.

As I kept trying to clean this IR filter I couldn't help but feel this wasn't even made of glass. Or like there was some kind of plastic film on top, as when you get something new and need to peel these off from the shiny surface it covers. Lightly tapping the filter (on the edges) with my fingernail I could tell that this wasn't a piece of glass, but some kind of polymer/plastic. Which to my knowledge would certainly explain why it can get so easily corroded!!!

?????

I get that the BMPCC 4K is a budget-oriented cinema camera, but using a piece of plastic in front of a digital camera sensor??? And how come we have to forage the internet for a suitable IR filter replacement when this happens?! There is no official replacement, none that Blackmagic Design sells or recommends. It's a guessing game.

Sure, I know about the RAWLITE Optical Low Pass Filter, which also reduces moiré artefacts in addition to reducing IR pollution, but this costs nearly half as much as a BMPCC 4K (and to my eyes, it makes the image a tad softer).

So, as a customer, I am dumbfounded by the lack of options from Blackmagic Design in the all too often event of someone's IR Cut Filter getting corroded (corroded, people, from tiny specs of rain). It's either foraging on eBay for a hit-and-miss replacement or paying around £350 for a good quality (and almost certainly made of glass) proper alternative.

Either that or send it to Blackmagic Design to have the filter replaced for another piece of plastic that will almost certainly get corroded in due time.

Thank you for documenting this so ably. It's very clear, and the pictures help. It does seem like something environmental related. That said, lenses of polycarbonate or plastic are common as well.

Thanks for the heads up! Is this something that would also concern the 6K or 6K Pro?

I got the same issue in BMPCC 4K MFT.

Followed exactly like you, and removed the IR Cut filter to learn that’s it’s oxidised, which is impossible to clean.

@BlackMagic Design please to pitch in and give some options

IMHO it’s not just limited to BMPCC 4K. This could happen for any BM camera line.

Found some options in Amazon, but not sure how good they are though.

IMG_7735.jpg (423.14 KiB) Viewed 1952 times

IMG_7735.jpg (423.14 KiB) Viewed 1952 times

IMG_7735.jpg (423.14 KiB) Viewed 1952 times

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https://rawlite.com/olpf-for-blackmagic ... camera-4k/

Hi [mention]Shaeedmalik [/mention], thanks for the link. [mention]Pedro [/mention] also mentioned about this in his original post, that this is so expensive that it covers almost half of the rate for which one could pick a whole used camera.

[mention]Blackmagic [/mention] must be aware of this issue and should make this filter available as spare for an affordable price.


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Kolari Vision also has a replacement filter with better IR cut for around 150 dollar I believe.

You sure that's an IR filter? I definitely get IR pollution if I don't add one to my lens.

These are IR filters, but they are not very strong, to avoid green tint and/or weak red.
You’ll definitely need extra IR filtering when using conventional NDs.
That’s another advantage of the RAWlite OLPF, it also adds better IR control.

I've never needed IR outdoor. Definitely some indoor lighting that needs it.

The main focus should be on what caused the spots, and how to avoid them. From the helpful pictures posted in this topic, I think as a precaution I will avoid using any liquid cleaning agent, even those intended for the purpose. Around here, pollen dust is sticky. A Rocket blower is what I would go to first, failing that, a dab with microfiber, not a rub. The microfiber attracts particles, it could be enough to get it near the dust spec and hit it with the Rocket air at the same time, before closing it back up. Problems like condensate, humidity, acidic moisture are not local problems usually, in the dry, arid U.S. west.

I've never needed IR outdoor. Definitely some indoor lighting that needs it.

Still using good ole 'redheads', Jim?

I seem to have the same problem - it's terrible.

I've been pretty careful with the camera, but after 4 years my BMPCC 4K is showing signs of what I believe to be corrosion on the inside of the IR filter. BM want me to send it in to be replaced, but it's expensive and I don't feel very confident that this problem wouldn't occur again if they are putting in the same material!

I agree with what some of you have said and think that BM should make a replacement IR filter available for us to buy at a reasonable price.

If anyone from BM is reading this, please listen to your customers!

After reading this post I went to check my three BMPCC4K. In the oldest one I encountered this phenomenon. So I expect that in the other two it is also a matter of time. This thing bothers me a bit.
Maurizio

Kolari IR filter