Return of Purple Fringing.

[rand thompson]

Rick,

I believe the non-removable OLPF on the Komodo is based on the removable "Skintone Highlight" OLPF on other DSMC2 Red cameras, someone correct me if I'm wrong. Maybe there's some Sensor/OLPF/Color Science interaction anomaly causing this also. Or maybe a Lens Coating/Sensor/OLPF issue.

 

[Graeme Nattress]

Two types of CA we normally see: axial and radial. This is axial. How do you tell them apart? Radial is least in the centre of the image and increases toward the edge of the image, and the colour fringes will be on the inner / outer edges. Axial is quite different - you'll get different colour fringes depending on if the object is in front (purple) or behind (green) the plane of focus. Axial CA is reduced by stopping down the lens. It is made more visible from the contrast of the edge. There's a theory posted on wikipedia on this CA that's it's some kind of sensor blooming from over-exposure and pixels spilling over into neighbours. I first tested that theory back with Red One when I first really noticed this kind of CA - and that theory is not the explanation. I tested it thoroughly and it's purely lens - not sensor blooming. Once we saw it we popped the lens onto our Canon DSLRs and guess what - same CA there.

Then I started noticing it in old films shot on film - you can clearly see it in the headlights of the cars in The Fury, for instance. Now I see it everywhere. What has changed is we have higher resolution cleaner sensors that don't hide this kind of thing, and the easy ability to pixel-peep.

Graeme

 

[rand thompson]

Thanks for chiming in Graeme!!

 

[Graeme Nattress]

Is that a hardware/sensor design change with Komodo, or a colour science/debayer/software-side change for all r3d footage?

It's tiny change to the colorimetry tables so that it travels with the R3D and doesn't require or depend upon an SDK change - that means there's no decode compatibility issues where if you'd opened the R3D with an older SDK you'd get a slightly different image.

It has nothing to do with CA and has no impact on CA. All that's happening is if you'd previously set the WB to 5600K, -3.26tint (as real world daylight is ever so slightly green) you'd now set it (more intuitively) to 5600, 0.0 tint. That's it. A simple change, but one that gives you an easier better starting point for your image.

Graeme

 

[Patrick Tresch]

Thanks Greame, I've learned something today.

 

[Rick Cook]

Thanks Greame!

So now does anyone want to be commissioned to create me a LUT that removes neon purple for these situations

 

[Mike P.]

It's tiny change to the colorimetry tables so that it travels with the R3D and doesn't require or depend upon an SDK change - that means there's no decode compatibility issues where if you'd opened the R3D with an older SDK you'd get a slightly different image.

It has nothing to do with CA and has no impact on CA. All that's happening is if you'd previously set the WB to 5600K, -3.26tint (as real world daylight is ever so slightly green) you'd now set it (more intuitively) to 5600, 0.0 tint. That's it. A simple change, but one that gives you an easier better starting point for your image.

Graeme

Yeah I knew it was OT. Just wanted to know if it was something that'd be seen in other RED cameras (*cough*DSMC1*cough*)... I'm guessing the colorimetry tables are changeable via firmware, but this is not a big enough change to bother doing? (Does this have anything to do with the updated WB colour picker in RCXp 52.2?)


Back on topic: While I understand these are higher res/cleaner sensors, that the CA doesn't show up nearly as much on every other camera you use the same glass with (some higher resolution than 6k) is probably quite frustrating. Best bet would be to go to a camera store and try a native RF lens. That'd get rid of a lot of potential question marks pertaining to lens performance (e.g. FD-to-EF/EF-to-RF adapting, modern lens designed for mirrorless, etc.) and allow you to decide whether it's acceptable or not for you/your work...

I'm more surprised others are not having the issue, which is the main reason I posted here. On most of my footage I can zoom in and find neon purple hits.

Coincidentally, I recently heard a horror story about the Komodo facebook group deleting posts/banning people if they said anything critical of the camera (no matter how constructive). Maybe that mentality has bled over to this sub-forum and people don't want to ruin the vibe by mentioning issues/concerns they have... That said, it's just as likely no one else is having similar issues because they're not using the same adapter/lens combo. Regardless, everyone here appreciates the heads up and now Komodo users who run into similar problems will have an answer moving forward.

So now does anyone want to be commissioned to create me a LUT that removes neon purple for these situations

Pretty sure I have Graeme's old ones. Presuming he doesn't mind, DM me your email and I can forward them over (admittedly they do remove quite a bit of purple, but they also work really well and are at least a blanket-application/set-it-and-forget-it process).

 

[Alex Stolpakov]

I am not at home atm so can’t upload any raw clips. Here is some quick dirty footage shot with a FD 50 1.4 stopped down to F2. Again, this lens does have CA but it never glows purple like this on any other camera I have shot with ranging from DSLR’s up to MiniLF. Every lens I own is glowing like this. Maybe CA is creating out of gamut color causing it to light up like this?

https://youtu.be/kbt9RunUtow

I like that everybody who is speaking about some kind color casts or noise or whatever in their cameras always say that other cameras don't have it. But never take the time to shoot side be side tests. This footage says nothing, because there is nothing to compare to.

 

[Graeme Nattress]

Drop me an email Rick - I made some a while back and you can try them.

Graeme

 

[Jan Vrzal]

I would like to know what lenses to use to avoid this issue. I saw many shots suffering this fringing on YouTube. Any recommodation for good and not expensive lenses for Komodo? I like Komodo' s footage but I don't like this purple and green fringing. And I wanna avoid this issue in my footage.

 

[Graeme Nattress]

Partly it's what lens to avoid for sure - some are better and worse than others. However, you can mitigate it in a couple of ways. First is to stop down. The other is to avoid really bright contrast where there's a lot of light coming through the lens. The CA is mostly visible on high contrast. I'm not enough of a lens geek to tell you which lenses are best, so I'm sure others will chime in there.

Graeme

 

[Aaron Lochert]

I would like to know what lenses to use to avoid this issue. I saw many shots suffering this fringing on YouTube. Any recommodation for good and not expensive lenses for Komodo? I like Komodo' s footage but I don't like this purple and green fringing. And I wanna avoid this issue in my footage.

SLR Magic APO primes, the DZO Vespids appear to also be apochromatic designs. Full disclosure, I haven't used either, but the stuff I'm seeing from these two look promising for the CA haters.

 

[Mark K.]

Is anyone finding CA exaggerated by particular compression ratios or debayer settings?

 

[Rick Cook]

Is anyone finding CA exaggerated by particular compression ratios or debayer settings?

I found it to be worse on Prores then R3D and also noticed it’s reduced at R3D HQ over LQ. That said, when I shot HQ and exported as Prores it was also popping more, so it’s just much less noticeable when looking at a 6K R3D in full resolution.

For what it’s worth to everyone, the shot I posted was 100% unscientific and intentionally searching out this effect that I had experienced while shooting to share with you. It’s not in 90% of the clips but any area where bare sticks were against a grey sky this occurred. I used no ND intentionally to rule out any color cast from that.

I don’t understand the negativity towards posting about this. I received my Komodo and am testing different scenarios and settings and came across this. It hasn’t occurred with my particular lens sets on other cameras, so thanks to the people here I worked through finding a cause and I am now figure out a best practice for avoiding this and as I am often not involved in post I am preventing it from being sent down the line.

Thank you so much to everyone that’s helped look into this and objectively looked at the R3D and reached out with solutions and knowledge.

 

[Christoffer Glans]

I would like to know what lenses to use to avoid this issue. I saw many shots suffering this fringing on YouTube. Any recommodation for good and not expensive lenses for Komodo? I like Komodo' s footage but I don't like this purple and green fringing. And I wanna avoid this issue in my footage.

If using mid-tier lenses like the CP.2s CN-Es, Sigmas etc. you will always need to stop down the aperture to get rid of CA. One of the biggest reasons top-tier lenses like Master Primes, Summiluxes, Signature Primes etc. cost as much as they do is that you can shoot with them wide open and not get any CA. So if you can't afford the top-tier lenses on the market, or if you use still lenses, you will always have to stop them down whenever you shoot high contrast scenes like the example in here. It will always happen on low-cost lenses, always and you have to test for yourself with your set of lenses where the sweet spot is. For me, stopping down the 35mm CN-Es from T1.4 to T2.0 almost completely erase the CA problems. But I don't have to do it every time in every situation. But if I'm shooting something like the clip in here, I will always do it to prevent CA.

So, you can't choose any lens outside the top-tier and expect wide-open performance to not have CA. My recommendation is to buy a set of lenses that have a very fast T-stop range, in order to be able to stop them down and get rid of CA without losing too much low light capabilities. This is the reason I chose CN-Es over the CP.2s, because you have to stop those lenses down too much before they perform. The Zeiss CP.2s have never been good in my opinion, due to the CA alone.

 

[Christopher A. Bell]

I don’t understand the negativity towards posting about this. I received my Komodo and am testing different scenarios and settings and came across this. It hasn’t occurred with my particular lens sets on other cameras, so thanks to the people here I worked through finding a cause and I am now figure out a best practice for avoiding this and as I am often not involved in post I am preventing it from being sent down the line.

Because a lot of people tie these cameras to their perception of their personal self-worth and self-esteem and take any perceived slight or criticism against the cameras as a personal slight against themselves.

I mean, c’mon. They’re cameras. And there hasn’t been a “perfect” one built, yet. If you don’t talk about them(good, bad, oversights, etc.), how do problems get fixed and following generations get better?

 

[Christoffer Glans]

Partly it's what lens to avoid for sure - some are better and worse than others. However, you can mitigate it in a couple of ways. First is to stop down. The other is to avoid really bright contrast where there's a lot of light coming through the lens. The CA is mostly visible on high contrast. I'm not enough of a lens geek to tell you which lenses are best, so I'm sure others will chime in there.

I noticed some hard CA on one of my still lenses in a high contrast situation. I don't see how the camera would be to blame for that since it's an inferior lens I used but is the consensus that the color science intensifies the spectrums in which CA can be seen, and therefor it looks like it's worse than on other cameras? Maybe just a tweak to a future firmware could take care of it or reduce it?

I've noticed that when underexposed, the image tends to go towards green, a lot. Maybe there's just some tweaks and balances needed on how Komodo and IPP2 works together?

Even if I know how to get rid of CA through grading, I love how photoshop RAW import use its CA reduction. Maybe we could see the addition of a CA reduction tool in the RAW settings (so we can use it in other software as well, outside of RCX). I much rather just have it in the RAW settings instead of having to make a node structure because of it.

 

[Alex Stolpakov]

I don’t understand the negativity towards posting about this. I received my Komodo and am testing different scenarios and settings and came across this. It hasn’t occurred with my particular lens sets on other cameras, so thanks to the people here I worked through finding a cause and I am now figure out a best practice for avoiding this and as I am often not involved in post I am preventing it from being sent down the line.

Its not a negativity, its a simple lack of objectivity from your side. You compare cameras without shooting them side by side. Its the same to say that you know the best
runner, but don't know how long or fast he runs.

 

[Phil Holland]

Just a quick note about comparing CA. More just information here.

When comparing results between cameras, keep in mind the format size as smaller formats will magnify the visual artifacts. i.e. using FF35 glass on S35 or S16 will yield different results.

Also big players are the optical pathway, color science, dynamic range, and even back focus.

In this case, this lens is a well known CA giver as it's a vintage lens. Stop it down 3 stops or expose aim for lower contrast conditions if going wide open.

 

[Kenneth C Merrill]

Don't post much on here anymore since I no longer have a Red camera, but this discussion piqued my interest.

I used to have a Red Epic-W, and I had similar purple fringing issues as you with my Leica R lenses. I still get some fringing with them on my Arri Amira, BUT the purple fringe was always exaggerated on the Red beyond anything I've experienced with other cameras. I suspect Red's color science doesn't know what to do with it; so it ends up making it worse. That's my non-technical, anecdotal diagnosis based on experience with these lenses on many different cameras (mostly Super 35), and finding that my Red had the worst purple fringe of the bunch.

Like everyone is saying, stopping down and minding high-contrast edges does help, but it does limit what you can do with your lenses. I found one very simple solution working on a fashion video once, where I had shot my Leica's wide open, and the talent was against a very bright background. The fringe was very distracting; so I simply used the color dropper in DaVinci to isolate that particular shade of purple, and I dropped the saturation to near-zero. There was still a fringe, but it was grey and hardly noticeable unless you knew what to look for. That's my quick and dirty fix.

Anyway, good luck with the Komodo! It looks like a pretty awesome for the price/weight. That said, it was always these weird little issues that I got with Red more than any other camera I've owned that caused me to move away from the brand.