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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

HDRx Noise/Artifacts

Michael Millichamp

Michael Millichamp

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So, I was shooting with an Epic this weekend, and had a shot of a tree I really wanted to get. Problem was, the sun was hitting the background pretty harsh. Never having done HDRx, I tried it out, and maybe it's my lack of knowledge of it, but I have found a good amount of noise on the tree I was shooting and degrading of the image. The background is fine, but the tree is noisy and jittery when I play back the footage.

Am I doing anything wrong? Maybe the blend is messed up. Im not quite sure, but I need the shot, and would rather not go back and reshoot it.

Thanks guys.
 
What compression were you shooting in ? Sometimes for shots with loads of detail it helps lowering the compression. Also, how does the footage look if you look at the 2 HDR streams separately ? Did you view it in full debayer quality ?
 
I shot it at 10:1, and im looking at it in a full debayer quality.

The two streams separate, look equality noisy.
 
May be the same issue as was stated in thread "Crazy Epic Artifacting." Since you were backlit and shooting 10:1 the issue would be compounded. Red is looking at this well known issue.
 
Teague, that is exactly what im experiencing!

A frame grab is fine, but in motion, it's pretty noticeably bad.

Hopefully there is a fix for it.
 
I have scene random noise pop up in strange places, like tree trunks, which is where I actually had noise issues myself. Its kind of mysterious, certain colors and tones and textures etc. just seems to get weird. The one constant is that it always seems to happen in 3/4 tones, the dark but not black areas of the frame. Using minimal compression and over exposing and then pulling back down in post seems to help.

Edit: I've seen two kinds of noise, typical tiny grain like noise, which i dont mind, and the strange crawling texture noise (for lack of a better description) I assume you are talking about the latter. It's my belief that this weird crawling texture we sometimes see is not simply digital gain or noise but something related to the debayering process and the sensor getting confused with the "pixel picking". It seems to be the result of inconsistency from frame to frame in certain tone and texture combinations which create a strange noisy crawling texture. Maybe I'm nuts, someone chime in here, I'd like to here what others have to say.
 
send me the shot, michael - i'd like to see what's going on. i haven't even tried/needed to shoot hdrx on my camera yet, but i guess i could test it. you obviously have a LOT of juicy and various levels of detail/contrast in the shot, which is extremely taxing on the compression. give me that thing and we'll see if it can be salvaged. :)
 
Yup, I'm sure you are getting the weird crawling noise that I have seen too.

Edit: This is the one area where film behaves a bit better. I'm sure these issues will improve in time.
 
The bottom image, of the tree trunk, looks like the compression went a bit wonky on it. That is not noise at all. It's a sign of over compression ( too lossy ). The soft blotches are the things I am talking about.
Perhaps the compression was 'overwhelmed' by all the detail, and something had to give.
Can you post an r3d still image ?
 
Im posting a red trim in a second. When it uploads ill edit this post.

I was in 10:1 and I just assumed that shooting the image in HDRx would be ok... Weird.
 
Mark Andersen said:
The one constant is that it always seems to happen in 3/4 tones, the dark but not black areas of the frame.
Click to expand...

I've seen this as well (on 2.05), and not just in backlit situations (also on overcast days in a dense forest). It's not HDRx specific. Brownish 3/4 tones are most problematic, so tree trunks definitely cause trouble. I've seen it in all resolutions when shooting varispeed with the best compression settings available, but most often with 2K. When it pops up, it wreaks havoc consistently within a given environment - so it seems like a compression problem triggered by certain variables. A fix would be amazing. A cap on frame rates that can't provide consistent quality would be a fair compromise.
 
Definately looks like a compression issue, nothing to do with HDRx in my opinion. When I shoot very complex (high detail) scenes like this, I try to use lower compression because higher compression like 10:1 has a hard time keepong all the detail. I remember a time (around buid 16 on the Red One) where such a tree made the camera crash...
Maybe exposing for the highlights and not using HDRx but a lower compression like 5:1 instead would have given you a better result... Would be worth trying.
 
Just FYI, the 2.0.2 (Alpha) seems to be the most stable firmare as far as image quality goes. We call this artifacts "snowstorm", and we've decided not to upgrade the firmware until this is solved.
 
Nook Kim said:
Just FYI, the 2.0.2 (Alpha) seems to be the most stable firmare as far as image quality goes. We call this artifacts "snowstorm", and we've decided not to upgrade the firmware until this is solved.
Click to expand...

As far as I know, we have not seen any evidence that these artifacts are linked to a particular build. If you do have evidence of this, please share. We are actively investigating encoding improvements for scenes such as the one in this thread. For best results with any high contrast, high detail scene such as this one I recommend using the lowest compression ratio possible.
 
Hi Matthew,

We've come to that conclusion after our tests and some posts on the forum. We haven't experienced this particular issue on the 2.0.2, but on the 2.0.5 and 2.0.8. We found a post about the same issue on 3.0.0 while we were testing the build so we decided not to upgrade.

The 2.0.2 is pretty stable except for one time when we had a checker board type of lines over the entire frame, which we issued a support ticket about. We were suggested to upgrade to a later build, but we didn't want to risk our customers with the snowstorm artifact since it was more frequent issue.

Good thing you guys are heavily investigating on the issue. I really want to be equiped with the RC3/RG3 as soon as this issue is solved.
 
Is there a possible fix if I send my footage off to Red or something?

I really want to use the shot, but I guess I might not...
 
I've been seeing the same thing on footage I shot over the weekend, they've asked folks to email in who are experiencing it, to rob at red dot com.
 
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