Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

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BabsDoProd

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Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

PostSat Sep 18, 2021 7:41 am

Hi, I'm currently looking at an URSA 12K as my go-to camera option for my next feature film and I've been looking at third-party solutions for IR-cut or anti-aliasing filtration and I just can't reason why Blackmagic wouldn't have changed their current sensor filters to fix the one clearly visible flaw in their cameras. IR pollution and moire issues have plagued BMD since the beginning, why are they still going along with the same flawed sensor glass covers that don't do anything except to be dust covers?

I have nothing but respect for BMD's cameras as the Pocket 4K has worked out really well for us as a small multi-purpose sidekick to our RED One MX and we're looking at going all in on BMD cameras for our upcoming projects but it's really inconvenient having to potentially risk our future camera and warranty for something that could be fixed in a product revision. What is the deal with BMD on this?
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Bromine 18

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Re: Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

PostFri Sep 24, 2021 9:15 am

BabsDoProd wrote:...I just can't reason why Blackmagic wouldn't have changed their current sensor filters to fix the one clearly visible flaw in their cameras. IR pollution and moire issues have plagued BMD since the beginning, why are they still going along with the same flawed sensor glass covers that don't do anything except to be dust covers?


Supposedly, it was explained back in 2012, as reported in other forum discussions. Though it’d be great if there’s a pinned official explanation.

To put it briefly, the design philosophy emphasized image sharpness, accepting moiré as a tradeoff, therefore disregarding OLPFs. And the sensor glass has mild IR attenuation in favor of letting the near-IR wavelengths reproduce what’s perceived by many as “great” skin tones.

Interestingly, even Arri – they officially state that they use OLPFs in all their cameras – use the same logic for IR filtration (https://www.arri.com/en/learn-help/tech ... ev-sensors), “Arri cameras use a high-end infrared (IR) and ultraviolet (UV) filter, which are custom designed to block enough of the spectrum to avoid false color effects … but that leaves enough of the near red spectrum to give skin tones a pleasant look.” At least their sensors’ IR filters seem to be doing a significantly better job.

I couldn’t agree with you more – an OLPF with strong IR filtration is a must for all video-focused and cinema cameras. Image sharpness, although crucial, shouldn’t come at the cost of spatial aliasing in the footage. And while a little bit near-IR wavelengths can be acceptable, it’s preferable to have a strong cut-off at a certain point beyond which the IR pollution cannot be mitigated well.

You’re not the only one puzzled by it. Here’s Newshooter’s Matthew Allard voicing the same thoughts – “I’m still perplexed as to why Blackmagic doesn’t include OLPFs in its cameras.” https://www.newsshooter.com/2020/07/17/ ... -thoughts/

Until BMD revise their design philosophy concerning OLPFs and IR filtration, I guess we have no option but to live with it.
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John Brawley

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Re: Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

PostFri Sep 24, 2021 4:26 pm

OLPF's take a hella long time to develop. Look at how long it takes for the aftermarket OLPF's to come though.

It's typically 18 months.

That means you're adding 18 months to the development cycle to tune an OLPF.

They are custom items.

They are specifically designed for every single sensor.

They aren't just "off the shelf" commodity items.

They require a great deal of SUBJECTIVE judgement about how much softening or detuning they are doing. What's good for some is too much for others.

Look at the many many threads and confusion on Reduser over OLPFs. And more so with their aftermarket ones. I know that one of the most significant differences in the DXL2 version of the RED is the OLPF, though they don't talk about it. I can't share the issues that Panavision have with the stock ones that come from RED, but it's not a small thing.

It's the same with the degree of IR filtering. The amount of IR (and OLPFs) can all greatly affect the colour science, something BMD is probably most revered for. You're arguing to mess with what a lot of people love.

BMD have chosen to leave this to aftermarket players. As the resolution increases the need for an OLPF diminishes. Most high end stills cameras now don't have an OLPF and haven't done so for years.

Rawlite do a great job, I've used their products and I know they are developing a 12K version. They've been working on it for 12 months... since the camera launched...and it's still not done. That's not because they are a small company. That's just how long it takes because it's HIGHLY iterative, take a lot of testing and energy to get right.

JB
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timbutt2

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Re: Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

PostFri Sep 24, 2021 5:56 pm

Rawlite is the best after market solution. I have it for my G2. As JB pointed out they’re working on one for the 12K. When they release that I’d suggest getting it.


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Uli Plank

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Re: Anti-Alias and IR OLPF - Why doesn't BMD adopt this?

PostSat Sep 25, 2021 8:43 pm

While I love it for the UMP 4.6K, I haven't seen much moiré with the 12K.
Maybe my lenses are not good enough. Neither do I see much with my Sony A7RII, which never got one.
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