FS7: Sony FS7 purple fringing - any fix?
- Thread starter Martin.G
- Start date
broughtonfilm
Well-known member
So the mattebox helps in controlling chromatic aberration? Or improves debayering process? Can it help with rolling shutter and other issues? What is the brand of your mattebox? I need it. Let's close this topic, the solution is the mattebox. And in this article where Art Adams describes similar, this time cyan artifact which was visible in XAVC but gone in RAW, was the mattebox the obvious solution too? http://www.dvinfo.net/article/acqui...-light-three-isos-and-many-possibilities.html
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Viddovation
Veteran
Please, feel free to discuss the issue. I have no problem with it being part of the conversation. But if you look back, you're the one who dismissed my points about optics, indicating they didn't belong in the conversation. Don't exclude my points, I won't exclude yours.
However, I don't agree with your suggestion that this is the same as the rolling shutter issue. Look - most of us don't work in situations where budget isn't a consideration. And absolutely, when push comes to shove, you work with what you've got. And the gear won't always be perfect. However, even when faced with limits on hardware, knowledge is what's king. Knowledge about optics. About sensors. About lighting. About digital processing. The more you know on these topics, the better tweaks you make even if the gear isn't everything you want.
If you have bright object in the frame, there's a good chance you also have some bright objects just off frame. Stray light that is too far off axis to be in frame can still hit the lens and wreck havoc... by hitting at an odd angle it can end up creating glare and washing out the image. The cheaper the glass (or more complicated the optical pathway, ie:Speedbooster, other optical adapter) the greater the problem typically. If you must have high exposure backlighting in a frame, it does tend to help to box off the light that doesn't make it in the frame.
Beyond matte boxes, providing fill lighting to reduce contrast and allowing you to expose darker may help. This can certainly be challenging in daylight on tight budgets where huge HMIs aren't an option. Reflectors, bounces, flexfills... everything you can grip... would make a difference. And if you can't do any of that - if you're so short on time or budget - then practically speaking, one should make composition adjustments to avoid problematic scenarios.
Ben Scott
Veteran
What are you talking about? The solution is to know how to shoot a scene and what to expect in certain environments and work around them to get a workable result. If you choose to shoot wide open, in blazing sunlight, without a mattebox, with lesser glass, with a frame like the one show,n then you have to expect issues down the line unless you plan for it a bit.
I've no idea what rolling shutter has to do with anything here.
You shouldn't expect even the best chisel in the world to make a sculpture without you contributing to the process somewhat.
Viddovation
Veteran
Um okay. *Reads Art Adams article*... Quote relevant bit:
Art Adams said:
Okay. So, the camera, when doing on the fly compression, appears to clip certain highlights in an unflattering manner. Said highlights, when processed from raw files in post (where said processing need not be real time, nor limited by horsepower of the camera) are rendered in a more flattering manner. Absolutely. Noted. Agreed, it exists. Agreed, it's not desirable or preferable. Agreed, wish it wasn't the case. Does it constitute a bug? Or a failure? From an engineering standpoint that's a much more difficult question to answer.
So, from what you're saying, we should dedicate this thread to complaining about a known camera limitation, that none of us have the capability to fix, instead of discussing practical work-arounds or "best-practices" to mitigate the effects of said camera limitation? I'm sorry, but that's not how I roll. We can't change what Sony provided us. Not here anyway. Go complain about camera limitations or bugs on the Sony Community site. Come here to inform people of bugs and limitations and to discuss practical workarounds.
broughtonfilm
Well-known member
How did I dismiss your point? In response to your post I said "It is not a question whether the CA is there in the first place or not, no one argues whether the CA fringes (specifically spherochromatic ones) are there." Does that dismiss your point?
The rest of your post above...why always such condescending tone? Where are all the assumptions from?
Ben Scott
Veteran
Viddovation
Veteran
Exactly. Your own quote of yourself - you treated the CA as a known issue (implicitly, known to the OP), and that the relevant issue was the digital processing one regarding XAVC/raw. Beyond that, your consistent dismissal of tips regarding optics, lighting, and other on set solutions has clearly demonstrated your primary interest in the digital processing element of this issue, to the exclusion and disregard of the practical elements raised my myself and others.
What is it that we can actually do about Sony's highlight handling implmentation for XAVC? What does beating that horse to death accomplish?
broughtonfilm
Well-known member
Look. It is a beautiful day today and I'm about to step out and leave this thread. You can give tips exclusively.
morgan_moore
Major Contributor
Personally I think it is the sensor/processing, sharp lenses will bring it out more.. I think I shot this on a canon cine lens but cured it no probs in resolve, somehow I managed to export different frames. it is 'cured' in the right frame by a bit of mag desat..
Moral? buy cheap glass.
Moral? buy cheap glass.
basspig
Veteran
I've seen this magenta fringe in Custom mode, but not Cine EI. Noticed it when shooting the moon a few nights ago. Very intense ring of magenta, almost like someone imported the frame into Windows Paint and drew a strong primary color circle around the moon.
I did a second shot in Cine EI and the magenta was completely gone. I'm not too concerned, because I haven't been using Custom mode as it seems noisier.
I did a second shot in Cine EI and the magenta was completely gone. I'm not too concerned, because I haven't been using Custom mode as it seems noisier.
Lenilenapi
Carbonite Member
Is this something you see before recording or only after on playback
Holy smokes, it appears around the moon too.
This looks like a huge mistake for me to buy this camera, as i intend to shoot alot of high contrast nature shots where i always have zero control of the lighting. Moon, stars, water, sun, leafs, waterfalls. Yes. Give me all of that.
But no other camera does what the FS7 does. This can drive a person mad.
This looks like a huge mistake for me to buy this camera, as i intend to shoot alot of high contrast nature shots where i always have zero control of the lighting. Moon, stars, water, sun, leafs, waterfalls. Yes. Give me all of that.
But no other camera does what the FS7 does. This can drive a person mad.
Nirv
Carbonite Member
Shame you got rid of your old equipment before being diligent and fully researching the FS7 then you might have discovered the FS7 is in fact a worth POS that exhibits purple fringing for fun. Sucks to be you...
Why so mean? Why are you pointing fingers before you know your facts?
My FS700 and Odyssey 7Q is still in my posession. This is the research i am doing.
And by looking at the response in this thread, is the FS7 part of this forum always this aggressive and anti-social? Im a little shocked over the bad behaviour here.
At any rate, there should be a fix for the purple fringing. Some say a firmware update, others say fix it in post. Is there a fix? A filter that can be applied in post? Something to alleviate this issue?
Ben Scott
Veteran
Martin,
I wouldn't worry too much about various scaremongering blog and forum posts. The fact that the camera is being used on plenty of commercials and broadcast shows, including Bloom's work on the Wonder List where he had very little control over the environment in some very technically challenging locales, should tell you that if you know learn how to use the camera properly and how to shoot properly you will more likely than not be fine.
I've not once had a single frame like the ones shown here in 9 months of owning the camera.
I wouldn't worry too much about various scaremongering blog and forum posts. The fact that the camera is being used on plenty of commercials and broadcast shows, including Bloom's work on the Wonder List where he had very little control over the environment in some very technically challenging locales, should tell you that if you know learn how to use the camera properly and how to shoot properly you will more likely than not be fine.
I've not once had a single frame like the ones shown here in 9 months of owning the camera.
Lenilenapi
Carbonite Member
I have to 2nd Martin's complaint. There is a lot of needless and irritating personal invective on this thread and others on FS7 issues. Please keep the posts professional and respectful folks. It ruins the forum and chases off those who have the most to offer.
Lenny levy
Lenny levy
Good to hear sir.
The FS7 looks like the perfect camera (well, it does not exist) and the camera i was hoping for in 2012 when i got the FS700, so i am really hoping i never see the purple fringing. There really is nothing else in this price range doing the same stuff.
But ive yet to find what exactly is causing the fringing. Sure, learn to avoid it, but how? What is the cause, and how to repair it?
Lenilenapi
Carbonite Member
Martin - one disapointment you may find compared to the FS700 is that the FS7 has poor auto focus. They just didn't bother to keep one of the better features of the FS700.
This purple fringing does seem difficult to pin down. I've never seen it as an owner since December and I often shoot custom, but I would like to know what to look for. I do know that similar purple fringing is often the result of chromatic aberration in lenses though.
Can someone answer my question above - Is this something you see in E to E or only after looking at recorded footage?
This purple fringing does seem difficult to pin down. I've never seen it as an owner since December and I often shoot custom, but I would like to know what to look for. I do know that similar purple fringing is often the result of chromatic aberration in lenses though.
Can someone answer my question above - Is this something you see in E to E or only after looking at recorded footage?
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Viddovation
Veteran
I'm honestly not sure why Nirv wrote the post I'm quoting you responding to, and I say that knowing that you haven't appreciated all of my posts. However, I don't think you were at all clear previously that you still had your FS700/O7Q. Here's your original comment:
said:
Not to go all English major on you, but your sentence construction is a bit ambiguous, and seeing as many people actively sell a camera before buying a new one due to cash flow issues, taking away the understanding that you'd already sold your FS700 is not unreasonable. So, call Nirv out for being rude, but I don't think you really ought to get angry at us for not knowing the facts. You could have easily said 'I'm considering selling my FS700 and O7Q, and buying an FS7, but I'm very concerned by these reports I'm reading about purple fringing. Is this a large issue, or am I worried over nothing?'. Such an opening to the conversation might have gone down a very different path.
Fixes to the purple fringing:
- Control your scenario: framing/lighting/lens
- Don't over expose
- Don't flare extra light in the camera
- Shoot RAW (Which, by the way, all things considered, you already have an O7Q... so keep it, and it will help you avoid purple fringing!)
- If you do shoot XAVC and have purple fringing, use Resolve or other color grading tools to reduce highlight saturation, either for the whole image, or as a power window for where the fringing occurs.
The purple fringing can be attributed to two separate issues:
1. Chromatic aberration - an optical effect, reduced by using better optics, by using existing optics at their peak settings, by avoiding flaring (which matteboxes can help), and by avoiding heavy backlighting or overexposure.
2. Digital clip artifact - It's been demonstrated that the XAVC encoding in the camera clips highlights in an uneven and unflattering manner that can produce purple fringing. This is induced to color channels being clipped unevenly. This was likely a larger issue in early firmware where there were still magenta white balance issues, and camera tests or reviews from that time period may be more concerned with this issue than warranted with today's firmware. Possibly will be further corrected with newer firmware, but don't count on it. Not present in raw, since raw doesn't artificially clip highlights. But what this fundamentally means is - something in the image was overexposed. Because this purple fringing is a clipping issue, it can be avoided entirely if you don't overexpose. The histogram and zerbras will help you do this. Don't trust the LCD screen alone - it may not be calibrated correctly, and the scopes/zebras are far more useful for verifying exposure.
The example frame you originally posted was over exposed. If they had exposed a stop or two darker, and made any final exposure push in post, the issue would not have occurred. This doesn't mean you're taking a camera advertised as high dynamic range and being forced to compose for small dynamic range. It just means you learn how the camera exposes and where the limits are. Camera tests like the ones you've referenced where this issue occurred frequently are done when people just get the camera and aren't familiar, and are intentionally pushing it's limits.
I know I've been a bit rough elsewhere on this thread, but hopefully you can take the information away from this post. It's a solid camera. It's not perfect. None of them are. It may or may not be a worthwhile move for your business from the FS700. But if you do get the camera, and you practice with it, learn it's quirks, you definitely can shoot great images that will make clients happy using the internal XAVC. But like any other camera, I advise taking time to test shoot it for yourself before plunging into a client shoot. That way you learn the limits, and you avoid pitfalls like the purple fringing.