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The (Video) Noise Saga
I’ve been attempting to track down the source of (what I perceive to be) a problem with my DVX100A. Almost all the footage I capture contains some amount of digital “noise” or “snow”. It is subtle, and some people don’t really notice it, but it is there. I can see it, and it bothers me that such a nice camera would produce such a noisy signal.
Specifically, the noise I am referring to is the ‘digital snow’ which appears in dark areas or mid-range colors (greys or other flat colors). Despite my best efforts, I have been unable to eliminate (or reduce to an acceptable level) the noise I get from my DVX.
First, a recap on my strategy to reduce noise. I have used the following guidelines when composing a shot:
– Lots of light. Wherever possible, more light is used to properly illuminate a shot.
– Correct white balance and black balance
– Master PED between -4 and -8
– Lowered Detail setting between -3 and -5
– Gamma curve “Black Press”
– Coring raised to reduce noise
– Chroma level downDespite all of this, I still get noise. I am beginning to think there is something wrong with my camera. I know that the image looks ‘good’ overall, however I still see noise in certain areas of almost every shot.
Here is the result of a small experiment. The following is a 6 second shot of a car across the street from my house, which follows the guidelines listed above for producing a clean image. f2.8, 24PA, zoomed all the way in, on an overcast day (so there is an even spread of daylight all around). I did not record this to tape — I went straight to my laptop over firewire and captured the clip in final cut pro. Here is the original raw DV file, with no modifications or filters, which is 18MB. Please go easy on my server, and download this clip locally and do not stream it:
https://mosey.org/film/2007/noise/car.dv
Here is a smaller version (4MB) of the very same clip which has been encoded with h264 using a compression setting that faithfully reproduces the original DV file pretty closely (iow, the noise is retained):
https://mosey.org/film/2007/noise/car-14-x264-aac.mp4
And finally, here is a screenshot indicating the areas of noise, which are visible when the clip is playing:
https://mosey.org/film/2007/noise/car-14-x264-aac.png
When you look at this clip (especially at full screen), you will notice noise in the upper left of the frame, in the area of the green door. You will also notice noise along the bottom of the frame along the entire bottom of the grey car. With the above settings in place I should be able to turn on my camera and capture footage that is clean and crisp and ready for editing. Instead, I am constantly plagued by noise, which makes its way into my editor and spoils (IMO) a good deal of my footage.
OK. So here are my questions, and requests for help.
– Do you see the noise? Am I crazy and there is really nothing out of the ordinary? I have seen many other clips of DVX footage that look fantastic, and have no noise at all. Why do I get noise?
– Do my settings listed above ensure a noise-free image? If not, what should I try next?
– Could there be something physically wrong with my camera? If so, what do I do about it?
– Is someone willing to go outside their residence and film a neutral-colored car in their neighborhood in such a way as to contain absolutely no noise (or, very little noise)? I want to be reassured that it -can- be done, and which settings were used to achieve it.
I hope the root cause of the noise I get in the DVX100A will be found, so I can eliminate it altogether.
Thanks for helping.
db
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9 Replies
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First, nice work in recapping your issue!
Boy, I’m hard pressed to say what you’re seeing is not “normal” for a camera with 1/3″ chips. Do you get this noise in the “standard” video mode of 30i? Remember, DV is 5-1 compression, and this artifacting sort of looks like what this might be.
The one thing I find of interest is that you state you’re running your iris wide open (2.8)outside. I might try this same scenario, only knocking it down a few stops to see if that helps.
In the QT movie, I downloaded it and doubled it’s size when looking at it and there is some noise.
What version of FCP are you using? Older versions have (IMHO) inferior codecs.
Does this footage look like this coming directly out of the camera into a monitor, or do you only see it AFTER it’s been ingested into your editor? This would be interesting to know.
Tim Scarpino
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Dave,
I thought of that as well, but since he was shooting outdoors at 2.8, I considered it unlikely he was using it.
But you’re right, it is something he should check.
Gosh though, it doesn’t look like AGC noise to me. If indeed it looks clean on a monitor between the camera and the NLE, I’m leaning towards a compression issue.
Good thought though!
Tim Scarpino
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[Tim Scarpino] “Boy, I’m hard pressed to say what you’re seeing is not “normal” for a camera with 1/3″ chips. Do you get this noise in the “standard” video mode of 30i? Remember, DV is 5-1 compression, and this artifacting sort of looks like what this might be.
This morning, I tried various tests with 30i. Same noise artifacting is present there as well. I also double-checked gain settings, to no avail. I am willing to accept this type of noise if I can get agreement from someone else that it is indeed ‘normal’, and to be expected from this camera. I just want to be extra certain about it before resigning myself to this situation (if it can be fixed, or alleviated, I want to know how).
The one thing I find of interest is that you state you’re running your iris wide open (2.8)outside. I might try this same scenario, only knocking it down a few stops to see if that helps.
I also tried this, in both 30i, 24P and 24PA. No help. One interesting observation: the wider I make the iris, the less obvious the noise becomes. It is still there, but reduced. The more I think about it, the more I think there must be some sort of switch or something which I am missing. I can “see” the clear and crisp image “behind” all the noise, and I feel like if I can find the proper switch, and flip it “off”, then suddenly the noise will just vanish and all will be well. Haven’t found it yet.
In the QT movie, I downloaded it and doubled it’s size when looking at it and there is some noise.
OK, good to know that someone else sees it, even when doubled in size. If you return it to normal size (100%), you should find that the noise it still there since now you know where to look for it.
What version of FCP are you using? Older versions have (IMHO) inferior codecs.
Good question. I am using FCP 5.1, capturing right from the camera (as a “Non-Controllable Device”) with DV NTSC 48hHz plus advanced pulldown removal (for the 24PA stuff).
Does this footage look like this coming directly out of the camera into a monitor, or do you only see it AFTER it’s been ingested into your editor? This would be interesting to know.”
Also a good question. I tried this just now with a small HDTV: there is no difference. The raw signal coming out of the camera has the same noise properties as the footage I capture in FCP. Very disturbing.
I would still like someone to head outside and try this with their own camera (since there is a small possibility that my camera is defective in some way). If someone could create a short 5-second clip, trying to create the cleanest and sharpest image possible. I would really appreciate seeing the raw DV footage from this experiment. I would be happy to provide some ftp space to upload this clip.
db
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[Dave LaRonde] “Y’know, nowhere in your post do you mention the word “gain”. Is your gain control set properly?”
Thanks for pointing that out. Yes, I have double checked my gain settings, and I am using no extra gain. There also does not seem to be a way to change the “value” of the L gain setting, only the M and H gain settings.
db
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[Tim Scarpino] “Gosh though, it doesn’t look like AGC noise to me. If indeed it looks clean on a monitor between the camera and the NLE, I’m leaning towards a compression issue.”
It could very well be a compressions issue. But could it be one originating inside the camera? If this is true, I kind of feel like there is no way around that (or is there? is there a way to adjust the compression inside the camera? i expect not, since it must be done in hardware). Except perhaps looking into something like this:
https://www.reel-stream.com/index.php
That seems excessive for my needs, though. I just want a clean image from the DVX. This weekend, I am supposed to get some raw DV footage from a friend who has the Panasonic PV-GS400. I am very interested in seeing it, and I will report back with the results.
db
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[dberton] “That seems excessive for my needs, though. I just want a clean image from the DVX. This weekend, I am supposed to get some raw DV footage from a friend who has the Panasonic PV-GS400. I am very interested in seeing it, and I will report back with the results.”
OK, I finally received some footage from a Panasonic PV-GS400. There is good news and bad news.
The good news is: there is a very similar noise pattern in the footage from this camera. Not exactly the same, but it is there. A subtle “dancing pixel” behavior, especially in the darker and mid-tone areas, and especially when viewing at full screen. Therefore, I think I am leaning more toward the idea that the cause of this sort of “noise” is simply the result of DV compression (which is 5 to 1).
The bad news: in comparison to the DVX100A, the footage from the PV-GS400 is -much- cleaner and more noise free. Both cameras appear to create some noise (again, this can be accounted for by the DV-compression theory). However, the PV-GS400 is head and shoulders above the DVX100A in terms of the signal-to-noise ratio. This dumbfounds me, and I cannot explain it.
Once again, I’d like to request someone’s assistance with diagnosing this problem in the DVX. If you could head outside on a sunny day, and take a 5-second shot composed in such a way as to produce the cleanest and most noise-free image, I would really appreciate seeing the raw DV footage. I have ftp space available, or you can use something like rapidshare.com. I am very interested in looking at someone else’s raw DV output in order to convince myself that my DVX is not somehow mechanically defective.
Thanks.
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[Dave LaRonde] “If you’re used to working with more expensive cameras that shoot better than DV-quality footage, the possibility exists that you’re simply seeing the sometimes-unfortunate results of DV video.
If you’re used to something like digibeta or DVCPro HD, DV can be sort of a letdown.”
Yes, I am trying to consider that, and thanks for pointing that out. However, I have not worked with a better or more sophisticated camera than the DVX to any great extent, so the only thing I can fairly compare it to is other people’s random DVX clips. And what I’ve seen has been either heavily post-processed (so that the noise is eliminated or obscured), or heavily compressed, or was shot using some sort of adaptor (anamorphic or 35mm). I have yet to see someone else’s raw DV footage from their naked DVX showing me a sharp and clear picture. I’m not trying to nit-pick, and I don’t think I am asking for too much. The DVX has an outstanding piece of glass inside it, and I am really hoping that the raw footage it generates is also outstanding.
I can also compare the DVX to the HVX (since there are many clips from that camera floating around). There is a clear difference here, of course. But I’m not looking for superior HD, just a clean SD signal. I’m not put off by lower resolution SD footage, but I think that that footage should be as “noise free” as possible coming out of the camera.
db
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[Dave LaRonde] “If you’re discriminating enough to see differences among various lenses, you can also see DV artifacts. Mating the DVX’s camera component to its internal DV deck is sort of like hooking a pricey Sennheiser mic up to a wire recorder.”
If that’s the way it is, then I’ll learn to live with it by making sure the exposure is correct which alleviates the problem (somewhat).
Care to explain how the DVX manages to win awards for cinematography? And why it is really the camera of choice for independent filmmakers far and wide? All these people accept the crappy DV compression as a fact of life, and move on (like I probably should)?
db
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What type of tape stock?
Has it been black balanced?
Does it do it in 24p? Are you in any of the P modes or just plain?
Also, I would do my tests in NTSC standard 7.5! Do you have another DVX where you can do a side by side?
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