Purple Noise at 2K

[Ian B. Johnson]

We've been using an Epic for high speed, but have been getting some bad results. It looks like noise, but the pattern and mostly purple color suggests something more is going on. Below are two full-res crops from the same day. Settings are as follows:

2k 2.4:1, ~200fps in 29.97 timebase
ISO 640
HDRx off
Redcode 6:1
180 deg shutter
5000K
Daylight

It was around 20F that day, perhaps the cold had something to do with it? Unfortunately we only have high-speed shots so there's not much to compare with. These shots have not been graded.

EDIT: Looking through the rest of the clips, I found one with some strange artifacting. See photo #4, (full frame grab of cat). Noise seems to be concentrated in the center of the image. Horrible artifacting around blades of grass.

EDIT2: Full-res TIFF here: http://dl.dropbox.com/u/43422607/A001_C010_1110OU.0001006.tif

 

[ericyoung]

How are you processing these shots from the R3D files?

 

[Gunleik Groven]

Blackshade?

 

[Ian B. Johnson]

How are you processing these shots from the R3D files?

The problem shows up in RedCineX, and these are exported as TIFFs, then JPEGs for upload. Also shows up in ProRes 422 exports. I'll make a full-quality TIFF available in just a minute.

Gunleik, we did not blackshade, though I'm not sure that would have rectified the artifacting in the cat image.

 

[Deanan]

Can you email me an R3D still?
deanan at red dot com

 

[Ian B. Johnson]

Email sent

 

[Wes Williams]

I'm having the same problem when shooting at 2K. It looks terribly noisy with the blue/purple pattern. I was actually uploading a video to come and ask myself. Will post link once it's up.

It's not necessarily 100% of the time either. Only certain times, of which I haven't figured out the common denominator.

Also, black shaded the few opportunities I had time to do so... it didn't make any difference from what I could tell.

 

[Wes Williams]

Here's where it's really apparent in this video:
http://youtu.be/l3sWNvzfWDY?hd=1&t=3m23s

Obviously just ambient lighting as we were shooting outside in this gorge. Didn't have time to black shade at this particular point, but I did earlier in the day however not likely with the same frame rate and exposure (which judging from some things I read could be the base of the problem). If that's the case, just isn't ideal for run and gun scenarios like this as it burns nearly half a redvolt to calibrate.

I feel like the same noise is in the 4K footage as well, just not nearly as apparent seeing as it's not being cropped in on nearly as much. After watching plenty of other 2K stuff though, I don't think this is a problem everyone is experiencing.

 

[Douglas Underdahl]

Purple haze, all around my brain . . .

(couldn't resist, sorry)

 

[Lonny Danler]

Black shading can often help clean up some noise at 2k 2.40 (make sure you're already at the settings you're going to shoot at). Not sure about the purple specks you're seeing exactly. 2k overcrank normally performs better in daylight than in tungsten. 2k 300fps at 7:1 even is cropping in on the sensor significantly and often produces noisy images (especially in tungsten low lit scenarios). If you're re-cropping for a 16:9 output, you're actually shooting about a 1518x853 pixel so you're upresing to get to 1920x1080. It's awesome the camera can shoot 300fps, just have to be extra careful when shooting it I've found.

 

[Robert Berger]

I was adviced to put the iso as low as you can when you go to 2K slomotion shots and do not under expose. So i did and it looks great. I shot a smiling faces and so we did whenn we looked back later too!

Robert M. Berger NSC
www.camlight.nl
Epic-X (Ed) 00274 and FRed One 1265 MX