Example of BAD Noise in 4K2HD ISO 2500

[taynos]

shot an interview with Laker guard Nick Young the other day in Los Angeles with FS7Q 4K2HD SLOG2. When I looked at the footage after the shoot, the noise was so bad I thought I inadvertently had set the ISO to 6400 as I had remembered my last shoot was a very low light space and maybe I had left the ISO mistakingly high for shooting a day time exterior. But when I looked at the camera setting, the ISO was set to 2500.

In addition I've noticed excessive noise when shooting in ISO 2000 (SLOG2) as well but not as bad as this. Yes, I was able to use Neat Video to remove the noise. No crushing the blacks did not reduce the noise. The noise is red in color and looks awful.

I have attached 4 images to show before and after Neat Video Noise Reduction also with a 300% Crop. These images are directly out of camera, no LUT or Color Correction applied.
I

How are you all handling all this noise? I don't think I have a faulty 7Q as I've shot with other shooters with a FS7Q 4K2HD set up in similar lighting conditions and found noise in that material as well. Having to use a de noiser for a perfectly exposed day time exterior to me is just nonsense.

What are you all doing to handle this issue. Do you all de-noise all of your footage? I typically expose using the waveform monitor and have tried many different exposure techniques, overexposing and pulling highlites back and crushing blacks, using the LUT on 7Q to expose to protect highlights, underexposing and lifting everything up. I still see the noise AFTER grading in Resolve, when applying the CD provided SLOG2 to REC 709 LUT.

Thanks in Advance. Also,

Here is a link to another thread about similar issue titles "Colored Noise" with 4K2HD
http://www.dvxuser.com/V6/archive/index.php/t-323167.html

 

[seanmc]

attachments don't work...

 

[taynos]

fixed. sorry about that

 

[Demistate]

You mentioned end of the day, it's possible the sensor was hotter than usual and that creates more noise.

 

[taynos]

Good thought Alexander but I have the same noise in the first shot of the day, in same lighting / location. Also we were shooting in shade, only for about 30 minutes total and it wasn't particularly warm that day. This noise has been present in everything thing I've shot in 4K2HD. Do you have SLOG2 4K2HD footage that is free from noise?

 

[hambulance]

It makes no sense to me that this would be related to the O7Q. It doesn't 'produce' noise. I have to be very careful to expose my fs700, I'd say it's a photographic principle and lighting issue where you need to expose the sensor correctly. You can use false color to help .

 

[ajp9039]

I also encountered a ton of noise in my test shoots with different O7Q and picture profile settings. Unless in specialized conditions that require SLOG2, I just shoot my 4K2HD in REC709 at ISO500. Far less noise and still flat enough to maximize dynamic range in most situations.

 

[seanmc]

Did you record AVCHD as well? Does it look the same?

 

[stefanhuberfilms]

i'd say expose more to the right, then bring down the overall exposure in post a bit. Ettr helps greatly to reduce noise.

 

[jshbckr]

Expose to the right (ETTR)... unfortunately I'm having a similar struggle with Slog2 if I'm not shooting RAW mode. LUTs don't really work well for it since it isn't designed for ETTR, but it gets really noisy if you don't do that.

And if your skin tones end up too high in the range when doing ETTR, they can get really weird looking when you bring the image back down in editing.

 

[Ebrahim Saadawi]

I also second exposure to the right.

*about the skin note above: sometimes people clip the red channel when ettr-ing, and when they bring the image down in post you get these skin issues, expose to right without clipping anything, not highlights and not colour channels, an RGB histogram is ideal for this.

 

[jshbckr]

I also second exposure to the right.

*about the skin note above: sometimes people clip the red channel when ettr-ing, and when they bring the image down in post you get these skin issues, expose to right without clipping anything, not highlights and not colour channels, an RGB histogram is ideal for this.

That's a good tip. I should look at my troublesome shots and see if I clipped the red channel.

 

[nyvz]

Yeah I found this in my testing of 4k2hd. The noise is similar in avchd but not visible because the compression and/or noise reduction smooths it out along with a lot of other shadow detail. It's interesting how lower compression ratios really show you all the noise that you never see because it is finally able to portray it. I've been meaning to compare 4k raw and would be interested to see how 4k prores will compare. I wonder if some of the noise is attributable to a fast debayer/downscale.

In any case 4k2hd looks great but you do need to be sure to expose up as much as possible to minimize it. I'd always aim for at least 1-2 stops over and as much as 3. That's the one nice thing about slog, it's fairly easy to just normalize the exposure in post with simple log offset (preferably pre-lut). That's one thing that will be really handy in when CD adds 3d luts to the 7q, recording/monitoring with your favorite LUT with custom recalibrated middle greys for correct looking images that are 0 through +3 stops over what slog is designed for, like what cine-ei mode does on f5/f55.

 

[nyvz]

It makes no sense to me that this would be related to the O7Q. It doesn't 'produce' noise. I have to be very careful to expose my fs700, I'd say it's a photographic principle and lighting issue where you need to expose the sensor correctly. You can use false color to help .

It is possible that noise could be worse on the 7Q compared to other options due to it's debayer or downscale or lack of noise reduction relative to other recording methods. Too bad it's not possible to record raw and 4k2hd at the same time to get identical footage to compare, but I set up a test once but never really got to analyze it that closely since it was very difficult to normalize the gamma on both. Is there a way to get 4K DNGs to look exactly like slog2? I can only seem to get a rough approximate in resolve through manually matching bmdfilm... Even debayering to linear and using lin-to-slog2 doesn't seem to match normal slog2. I hope to do a more in depth test later, but it'll require a bit more work manually matching the footage for comparison.

It will be a lot easier to judge on 4k Prores footage since it will also have a matching slog2 gamma on it.

 

[hambulance]

From those screen shots I see the area that has no noise and is exposed correctly is the background area. While all the foreground and subject is underexposed. You could also try to bounce (or provide) 1-2 stops of light onto your subject and he would be crystal clean with just a bit of noise in the background shadows you have there and fix easy.

The FS700 sensor needs light, when it's underexposed you get noise.
When I've shot underexposed in 2k raw, it will behave the same.
When you shoot to AVCHD the noise is still there from the sensor but it gets 'mushed' about a bit. 'Mushed', by the way, is a technical term that only ultra professional super pro's with big boy hats use.

I used to use a GH2, same deal, but the FPN (or pattern of noise is horrible). The FS700 noise is beautiful in comparison, like a film grain.
You could try a BMPCC and you'll again get noise where you under expose the sensor, even in 1080p RAW or Prores.
If you don't like noise at all you could go back to shooting on a Canon where you get blacks being crushed in camera, or whatever kind of compression voodoo they use. Although I'm pretty sure ISO 3500 on an underexposed Canon would be noisy too.
You could use an A7s which responds well to low light and you'll be dealing with a different beast again (with a lack of internal ND filters).

I accept that the FS700 is not a low light camera and is why I would pair it up with the A7s for when light is at a premium (or instead with appropriately fast lenses).

I have found that exposing the FS700 (when trying to get the best image quality) is actually a very finicky, precise and delicate task. ETTR is not 'the hammer' answer, once you go too far to the right the channels clip (as mentioned) but the visual info in highlights gets compressed in the video stream.

To get a good exposure is a fine line, I thought about writing a blog post on it and my experiences, but it is actually very hard to get right, you can't just kinda over expose or under expose and hope to have clear noise or conversely just recover image from highlights. Expose in the middle - just a nudge, a smidgen, to the right.

Use the false colour and settings to match up with the profile. REC-709 will be way more forgiving because of the sensor and running at 500 ISO (I use this and get lovely dark areas). For S-log2 you can set blue at 15 and purple at 30 - this can be your noise zone. Set green to 50-70 and try and get the subject of interest or skin tones in this range. then put your yellow and red up high to where your acceptable highlight recovery or clipping is. And set your scene via false colour option on the O7Q and you wont be disappointed. Further to that, set your false colour to some of your own tests before you shoot a production interview.

Hope this helps

Edit:

Here's and example from me. I've hit the same problem when in high dynamic range environments, where you don't want to blow out the background.

This is in S-log2 4k2hd. You'll see where I'm trying to expose this guys face properly, using false color but I'm literally riding the noise floor where his face is shadowed. You will see that where he has light on his face there is no noise as this is what is exposed correctly. I did have a small light on his face, but it was not enough to get it up higher. I should have increased the exposure and lost a bit of the background, instead of trying to expose the entire dynamic range of the scene. Of find a way to equal the light level on his face to the background (by adding more lighting somehow).

So I would class this as a near miss or a slight fail to my own standards, but it's about getting experience and honing your lighting skills and/or ability to evenly expose any given sensor you are using.

 

[Clermond]

great summary,hambulance.

It hits my own experience. With the output of the FS700's RAW you have no internal noise treatment like in AVCHD
The noise of the FS700 RAW (and also 4K2HD) is present but is fine and looks more like film grain than digital dirt.
It's easy to treat with NR filter like neat video bus mostly I keep it as it is. Here's sample I recently shot:

out of camera:

100%

q&d color treatment in FCP X, no NR. You see some "grain" but it disappears when the clip is playing. If people go for pixel peeping at your videos your story is probably boring :cheesy:

 

[Colinelves]

Lots of very good advice there: Hambulance - your suggestion of setting the false colour to the Rec 709 levels is brilliant by the way!

What your finding, Taynos, is that high DR is no free lunch: a lot of the 'extra' stops you get are in the shadows where there's a lot of noise. The problem with slog2 on the FS700 is that skin tones tend to get pushed into those noisy stops when you're trying to make use of the 'full' 13.5 stops or exposing 'correctly'.

This is true of high-end cameras like the Red and Alexa as well, albeit to a lesser extent, they have better sensors and better on-sensor noise reduction technology. The A7s, by all accounts, has truly superb noise reduction, which is why it can operate at such insanely high ISOs and has such high DR (a hair over 14 stops by all accounts): the sensor is really good at killing the noise.

Also, it doesn't help that you were adding analogue gain to the image, which will also increase noise (and shorten DR) - ISO 2500 means you must have added at least +1.5dB (I think).

I've found I tend to ETTR with Slog2 (I set the O7Q zebras to 106% and make sure I never let them come on unless it's in the bright areas of a burnt out window) or I use the false colour and put skin highlights hitting the yellow preset levels (around IRE 70). When I can, I set my light meter to ISO 800 and expose to that. I never use the LUT, it's pretty useless to me.

 

[Gene Sung]

From those screen shots I see the area that has no noise and is exposed correctly is the background area. While all the foreground and subject is underexposed. You could also try to bounce (or provide) 1-2 stops of light onto your subject and he would be crystal clean with just a bit of noise in the background shadows you have there and fix easy.

I second this, you exposed for the background (the white, daylight part) instead of exposing for the Shadow (the subject). The subject is about a stop under (maybe a bit more). If exposed correctly, the background daylight part should have just been white.

4K2HD is not like RAW in that you cannot really expose to the right. I usually just do the middle or even slightly under on extremely bright days. When I expose 4K2HD to the right, the highlights get blown out and cannot be recovered like in RAW.

Edit: I will say in this case, you would have been fine exposing to the right (if there was enough light to allow it) because the subject is in the shade.

 

[cuervo]

The outstanding answer to your question is the ubiquitous, ETTR, with all the caveats that go with that advice. This is the solution for, as-yet, unaquired footage. But, for that existing footage with all that unseemly grain, I've had terrific success with Neatvideo. It really does an amazing job of cleaning that up.

 

[taynos]

The outstanding answer to your question is the ubiquitous, ETTR, with all the caveats that go with that advice. This is the solution for, as-yet, unaquired footage. But, for that existing footage with all that unseemly grain, I've had terrific success with Neatvideo. It really does an amazing job of cleaning that up.

I want to thank everyone for the discussion / the frame grabs etc....I'll admit the talent is slightly underexposed in this case, this is partly due to the fact the shoot is for VICE, and their mantra is everything is to be very raw, no lighting, they even are touchy about using a bounce. We were in a touch spot being under umbrellas on the patio and I think my BG would've gone nuclear if I opened up. But I do agree I could've probably had a half a stop or so that might've helped. But as mentioned in the OP, I have shot ETTR on different shoots and 4K2HD still exhibits considerable amounts of noise with daylight exteriors even at ISO 2000.

I think the most enlightening thing I've learned is that the 7Q does not offers any noise reduction, so we have to use NR in post if you are looking for a cleaner, silkier image. Out of camera, 4K2HD looks almost like a high grain film stock, like ASA 800 / 1000 before NR is applied.

Also- why must SLOG2 have a minimum of 2000 ISO? Why can't we get something like 700 / 800 ISO?