[answered] flare and ghosting

[bevan goldswain]

I've had my Dragon for about a week, apart from the beautiful colours + dynamic range I have come across a pretty consistent problem: Crazy flare and ghosting.

Whenever I have a light source above the lens i get the most horrible looking flare. This is no normal lens flare, it doesn't slowly bloom as you aim towards the light... no, one minutes it's not there and then the next - FLASH its all over the place.
The flare also streaks directly down from the top, very strange.

When I get this flare you can see light grey horizontal lines running across the picture.
When the light source is more diffused the flare represents more as ghosting - like what you see on old CRT t.v. sets.

I have read a thread on here about some crazy flare when using the Nikon aluminium mount, (which is what I have been shooting with) I'm not sure if what I am seeing is the same problem the other Nikon Aluminium mount users have had, or if this is something new.

Attached are some screen grabs from RedCine. I have sent them over to RED this morning, waiting for a response from them.

Anyone else out there seen anything like this?

 

[bevan goldswain]

Okay I just realised that you cant really see the weird horizontal lines in those screen shots, here is a closer look at the bottom right corner.

 

[David Battistella]

What lens?
Are you using a matbox?
exposure details?

theres a good chance I have the lens so I can try to duplicate.

If there is no lens shade or matbox then high noon backlight can produce these flares. But I haven't seen anything like that since the gate flare was fixed a long time ago.

Battistella

 

[bevan goldswain]

Nikon 17-35 ED 2.8
Happens at any zoom setting.
I think I was shooting mainly between f5 - f8.

No matbox.
No Filters.

I get that lens flare happens, I know a lens aimed near the sun will flare, but this light burst seems to be in addition to my normal lens flare. It's like, as I point the camera towards the sun I can see my lens flaring, slowly, more and more. And then I get hit with this burst of light.

Then when the sun is actually in the shot the light burst goes away, it only happens when the light source its just out of frame.

 

[Gavin Greenwalt]

This looks very much like a lens mount flare. It very closely resembles the old flare before RED installed a little black piece of velvet around the OLPF.

 

[Phil Holland]

This is what traditionally is called gate flare. It happens with all cameras (Red, Film, Alexa, etc....) when a strong source flares into a lens at a particular axis. Usually from frame top, bottom, and occasionaly left and right. Some lenses are more prone to this than others.

The lines you are seeing are likely the cast shadow of the photosites on themselves based on what I'm seeing. On certain DSLRs you can actually illuminate the pixels in such a way that you can clearly see the photosites even.

Some DPs use this effect for a particular flare aesthetic. However, to avoid this proper use of a matte box and/or french flag is necessary to combat the light from the source.

Interesting in the past there was a new OLPF Port Bushing that Red provided for Mysterium-X cameras that minimized this effect a bit, though it still would happen - it was just more wrangled. Inside Dragon you will see a little plastic circle/rectangular frame in front of the OLPF. This is the OLPF Port Bushing. If that is removed you can get some fairly interesting flares. Typically you should do that though.

This is standard cinematography related stuff. This is part of the reason that matte boxes are an essential piece of kit.

 

[Phil Holland]

To expand on this a bit. The 2nd example of the girl looking over her right shoulder the reason there is a gap in the flare is that the sensor box is casting a shadow/blocking the light that is causing the flare. The two darker rays are probably where light is getting blocked by the supporting frame in the window or door behind her.

A matte box with an eyebrow/top flag would eliminate such a thing.

 

[bevan goldswain]

I've used the same lens on many different makes of Nikon and Canon cameras, and I have never seen any flare like this.

I am not against lens flare. I like lens flare, but when I am getting with the Dragon is really horrible.
I know that a Matte box will stop the flare, I stopped it myself by shading the lens with my hand. But stopping the flare is not something I want to do, I just want the flare to look like a normal lens flare, not Armageddon.

So my understanding then of gate flare is that something between the lens and the sensor is reflecting light around in ways it shouldn't. Does that sound about right ?

I've read on another thread that people with the Nikon aluminium mounts were having this problem and some ended up using matt black spray paint on the mount.

 

[Phil Holland]

I've used the same lens on many different makes of Nikon and Canon cameras, and I have never seen any flare like this.

I am not against lens flare. I like lens flare, but when I am getting with the Dragon is really horrible.
I know that a Matte box will stop the flare, I stopped it myself by shading the lens with my hand. But stopping the flare is not something I want to do, I just want the flare to look like a normal lens flare, not Armageddon.

So my understanding then of gate flare is that something between the lens and the sensor is reflecting light around in ways it shouldn't. Does that sound about right ?

I've read on another thread that people with the Nikon aluminium mounts were having this problem and some ended up using matt black spray paint on the mount.

It's not really horrible. In motion picture cameras this is expected and common behavior. Different sensors and sensor boxes are going to reveal this in different degrees with different lenses. The lens you are using is going to perform differently due to those design variations behind the glass.

Watch this Tribute to Roger Deakins video at around the 14 second mark:

That is gate flare and not from a Red camera. I can provide you a million examples of this across point and shoots to DSLRs. It happens. It can happen. There is one thing you can do to combat this.

The solution you are looking for a is a matte box or a french flag.

 

[CJ Roy]

Bevan, take a look at the OLPF port with the lens mount removed.

This looks exactly like the original Epic MX's flaring issue without the OLPF Port Bushing. The port was highly reflective and causing the flare. Prior to Red sending out the port bushing fix for the issue, people were making their own solutions.

 

[Bérenger Brillante]

WHen you shoot water with sun refelctions that flare is awesome.

 

[Sidney L. Plaut]

Bevan, take a look at the OLPF port with the lens mount removed.

This looks exactly like the original Epic MX's flaring issue without the OLPF Port Bushing. The port was highly reflective and causing the flare. Prior to Red sending out the port bushing fix for the issue, people were making their own solutions.

except that "pixel" pattern looks horrible. I have never seen that on RED 1, 1mx, Epic MX, or Alexa.

 

[bevan goldswain]

Yeah it does look pretty awful.
i get those horizontal lines every time I point the camera at a bright light source.

RED said they would have an answer for me soon, I'll let you all know what they say.
in the meantime, if anyone else has this gong on please post it here.

 

[Bohdan Klos]

The solution you are looking for a is a matte box or a french flag.

Flags will help but on occasion one wants some flare those pixels are rather nasty.

 

[John Marchant]

The strong gate flare is a Nikon mount thing, not a Dragon thing. The lines within the flare are probably resulting from the very oblique angle of incidence of the bounced light causing the flare, presumaby interacting with the sensor surface

If you really don't want to solve this with a mattebox, you can see substantial improvements by using a little black flocking or fine self adhesive felt on the flat inside area of the mount - there's a plastic surface which seems to be the issue. The relatively oversized image from the full frame glass hits the plastic section whose surface is perpendicular to the sensor, when the light source is well out of frame, and bounces up across the face of the sensor.

Very similar to any gate flare, but quite pronounced on the Nikon mount, and more so with full frame rather than APS-C glass.

 

[Bob Gundu]

It's definitely the Nikon mount and not a dragon sensor. I get this on my red Nikon mount and not as much on the optitek mount.

 

[Sean Rawls]

I've seen the exact same issue using approved Nikon G lenses on a Dragon. The issue went away going to 5k but that's not why you got a Dragon With really careful flagging I was able to deal with it on set.

 

[Justin Chin]

To expand on this a bit. The 2nd example of the girl looking over her right shoulder the reason there is a gap in the flare is that the sensor box is casting a shadow/blocking the light that is causing the flare. The two darker rays are probably where light is getting blocked by the supporting frame in the window or door behind her.

A matte box with an eyebrow/top flag would eliminate such a thing.

Yeah I got the same port shadow with Xenons on my EpicX at 5k and 4k resolutions.

 

[bevan goldswain]

Yeah I got the same port shadow with Xenons on my EpicX at 5k and 4k resolutions.

What mount were you using with your Xenons?


Has any one tested the different between the Nikon Aluminium and the Nikon Titanium mounts?

 

[David Battistella]

Black matte paint is your friend. Any professional lens tech has the right stuff. It takes a couple of minutes and reduces these internal reflections. As Phil stated a Matte box is also your friend. or at least a French flag.

Battistella