Sun appears as a Black spot during mid-day

[jourman]

Hi there,

I was shooting the a shot in front of the sun during mid day and the sun itself apeared as a magenta black spot
While shooting on 2k, 2:1, Redcode 28, 120fps, shutter 1200, Iso 200, T5.6

I was wondering if anyone has encountered this problem, and has any insights.

 

[Dan Hudgins]

Solarization

Solarization

I was shooting the a shot in front of the sun during mid day and the sun itself apeared as a magenta black spot

I think I saw Solarization in one shot in CHE #1 in the car headlights, it seems to be a known defect in some CMOS type sensors, I think overflow in the A2D circuits or something. Some brands do not do that, but maybe there is a patent on the way to prevent it. Could also be caused by overflow in image processing software/hardware.

I was wondering about REDONE having that problem since I was talking about doing HDR with two cameras, the Solarization in the bright camera could be a limit on how much extra dynamic range you can get. REDONE seems OK for three stops past clipping, the sun would be more than three stops hot I would think? Anybody got a spot meter to check the brightness of the sun's disk vs. a white card in full sunlight?

 

[Uli Plank]

Did you use an infrared filter? The sun sends heaps of it. I've only ever seen this effect from the sun, it must be far over 3 stops. Normally it's not a big thing to cure it, the black spot tracks very well and you can just cover it with white…

 

[Cüneyt Kaya]

why doesnt the cam itself cover it with white instead of black?

 

[Jeff Kilgroe]

why doesnt the cam itself cover it with white instead of black?

Most likely because it would require too much internal processing in terms of analysis and alteration on the fly. The camera does little more than collect RAW sensor data and process quickly downsampled footage for monitoring.

This "black sun" effect has been around since the very beginning. It can show on any lights that are over a certain brightness. Not hard to replicate with the sun in frame, but relatively easy to fix in post and can often be corrected out with a good curve applied, no need to track and cover in every situation.

What I find disturbing is the amount of stuff shot on RED out there that leaves the black sun in place in the final delivered footage. FWIW, the RED One is not the only camera that has this problem. I see it a lot on surveillance cameras and scientific imaging equipment that don't have unnecessary internal image processing.

 

[Cüneyt Kaya]

there should be no internal tracking.
asfaik...the color black is a visualisation of the overclipped area (sensor protection) it should be easy to change black against white

 

[Radim Schreiber]

This sound familiart. Something that Canon EOS 5D Mark II still digital SLR had. Canon has released firmware that replaced black dots with white ones and everyone was happy since.

Photos & video BEFORE firmware:

http://www.coolest-gadgets.com/20081219/canon-has-a-black-dot-problem-with-the-new-5d-mk-ii/

http://www.youtube.com/watch?v=mFaZXYhHrUI

Post a sample, it might be similar issue since Canon uses also a CMOS sensor.

 

[Jeff Kilgroe]

there should be no tracking interanl.
asfaik...the color black is a visualisation of the overclipped area (sensor protection) it should be easy to change black against white

The black is indeed overclipped or overloaded photosites. It's not necessarily an issue of tracking. First and foremost, it's an issue of additional data analysis. First of all, we don't know how the sensor reports the overloaded photosites. Do they show as a full saturation value, or do they return as a zero or other low value due to a reset or roll-over? While it is easy for a person to see it, the camera itself may not be able to determine the difference between a black spot from an overloaded light source and a black object in shadow. We also have to consider that with the bayer pattern sensor, any proper fixing of these overloaded values would involve a debayer and demosaic, yet again something that is not done in camera.

Given how many times the spot can be fixed with a good curve, I'm of the opinion that it's showing really high values, so is probably something that can be fixed with the debayer opration. IMO, this is something to be fixed within the R3D software tools. So add it to the long to-do list of features and fixes for the RED tools and SDK.

 

[Joel Kaye]

Hi there,

I was shooting the a shot in front of the sun during mid day and the sun itself apeared as a magenta black spot
While shooting on 2k, 2:1, Redcode 28, 120fps, shutter 1200, Iso 200, T5.6

I was wondering if anyone has encountered this problem, and has any insights.

That's because the end of the world is nigh.

Or it's the "black hole sun" bug RED has. The center of all very overexposed points of light turn into a magenta/black spot. Raise the highlights in Red Alert or RedCine and it'll probably go back to blown out. Otherwise you'll have to do some work in After Effects.

I shot a concert recently and some shots were up into a zillion par cans. A zillion little black hole suns. Raising the curve in post fixed it easily.

 

[Sam Roberts]

I just shot a flag flapping in the wind with the sun behind it with the sun being intermittently revealed as a black circle. Could someone explain the best way to make it white? I have After Effects and the newest Photoshop as well as all the Final Cut Studio programs. Which is best?

 

[Stefan Scherperel]

Ihave found that using red cine and the highlight slider can usually take out a black sun.

 

[Brian Harbauer]

Film will do it too, I remember a piece by Ansel Adams where Adams specifically exploited this to get an effect he was after.