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video noise? (channel)
- Thread starter dvdguy
- Start date
I'm just about to run out the door, but I'll give you a quick answer - noise is caused by not having enough light. If your blue channel's noisy, there isn't enough blue light. If the whole image is noisy (as the one you posted in the other thread was), you need more light overall, so that the gain/ISO can be turned down.
(You can use noise removal plugins and standalone applications, but these should be a last resort.)
(You can use noise removal plugins and standalone applications, but these should be a last resort.)
could you further explain what gain/ISO stands for and what is intended for? I heard of the term while reading some posts but never really got to familiarize it.
I read that the more you increase the gain/ISO the more noise you get? True?
ISO is a measurement of film speed. The larger the ISO (from less than 100 all the way to 3200 or more) the "faster" the film is, and the less light it takes to burn the image on the negative. The trade off was that the larger chemical particles used on faster film left a visible grain on the picture, though this grain can also be used for artistic effect. Digital sensors emulate this behavior. The higher you have the ISO set, the less light it takes to capture the image, but the more "noisey" the image will be. Fim grain can look very cool, digital noise generally looks like crap.
Thanks for the thorough explanation
. So the same basically goes for video, just that the downside is it looks like crap? lol. -So its basically best to have the gain/ISO higher? How do I know how high my gain/ISO is? (cause I read some people said that it varies, but I have no idea on what).
-So if I reconstruct your sentence a bit... The lower the ISO, the more light you need, but less "noisey" the image will be?
-How about if I have my ISO set pretty high, and still add more lighting, will the grains be removed?..
-Oh on the side note, what is f 2,8...f 5 ...etc etc. ? not sure what that really means. shutter speed?
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I recently did a write-up on this very subject on another board. Since I'm not allowed to link to it directly, I'll copy-paste what I can to here:
The Cause:
The camera has a sensor in it that is basically a grid of little tiny photoreceptors. Every photon of light that hits a photoreceptor is absorbed and increases the electric charge in that photoreceptor. After the exposure time is up, all of the charges in each photoreceptor are dumped into circuitry that measures how much charge was in each cell. The greater the charge, the brighter the pixel.
Note that these photoreceptors only measure brightness and not color, so to get color you either have to place an alternating grid of filters over the sensor, or you have three sensors (one each for red, green, and blue) and a prism that splits light out to all three.
Noise comes from two causes, but the primary cause is photons aren't the only thing that can increase the charge held in each photoreceptor cell. Heat can randomly increase the amount of charge by just a tiny little bit. In direct sunlight this isn't too much of a problem since there are a lot of photos hitting the sensor and they tend to overwhelm the noise.
Low-light is where the noise becomes apparent -- there are fewer photons hitting the sensor so the charge amounts are run through an amplifier (so the generated image will be of the proper brightness) which also amplifies the effect of the random charge noise introduced by heat. The greater the amplification of the charge signal from the sensor, the greater the noise. This is why the more sensitive ISO settings on a DSLR camera are grainy. It's the same effect.
The other thing that causes video noise is the photons themselves. Photons bounce around willy-nilly so the number of photons will vary slightly between photoreceptors and between frames for the same photoreceptor. This accounts for some of the low-level noise you see in a daylight video shot. Once again, in low light the amplification applied to the signal from the sensor will also amplify the slight photon variations into larger variations.
The same thing happens in video filters. If you have an image or video with a little grain and increase the brightness or contrast it will amplify all the little variations and result in more visible noise. The reverse is also true: reducing brightness or contrast will lessen the noise. If you can overexpose your video (without blowing out your highlights) and then darken the exposure in post, that will reduce some of the visible noise. Note that this only works if you increase your exposure by altering your aperature or shutter speed. If your video camera brightens the exposure by simply amplifying the sensor signal (this is how cheaper cameras do it) then you'll gain nothing since the overexposure will introduce more noise from the start.
As for why you see different amounts of noise in different colors -- this might be due to variations in the physics of the sensor itself, but the main reason is because of how the human eye works. The eye is more sensitive to brightness than color, and is more sensitive to reds and greens than blues. Highly-saturated colors are bright, so your eye will pick out noise variations more easily than in darker colors.
The Solution:
Aside from only shooting in bright light (eg. daylight or a fancy lighting setup), I've only found one program that successfully combats video noise acceptably: NeatVideo. I've been a user of their still-image noise removal program, NeatImage, for years but I just recently purchased their video filter and it works beautifully.
The best way to use this program is to get a grey card (or just film a blank, solid area) out of focus (so the only thing the camera sees is noise and not details) at the same camera and light settings your scene will be (or was) shot in. NeatVideo analyzes the noise and can then filter it out of the video with a pretty staggering degree of success. It also has an "advanced" mode that lets you adjust how much filtering to do at different noise levels and lets you separately control how much filtering is applied to the brightness and color channels.
You can remove noise from existing video without shooting a solid out-of-focus shot as described above so long as there is a solid area in at least a single frame of video that you can select to tell NeatVideo "this is supposed to be a solid color, so analyze this part of the frame and treat all variations as 'noise'". This calibration can then be applied to the entire video clip.
It's an easy tool to use and if you only need to work with standard-def video, the Home version only costs $99. (I work with higher-resolution footage and so sprung for the $199 Pro version. Worth every penny.)
Examples:
(click the image for the non-cropped full HD frame)
Original:
NeatVideo noise reduction:
The Cause:
The camera has a sensor in it that is basically a grid of little tiny photoreceptors. Every photon of light that hits a photoreceptor is absorbed and increases the electric charge in that photoreceptor. After the exposure time is up, all of the charges in each photoreceptor are dumped into circuitry that measures how much charge was in each cell. The greater the charge, the brighter the pixel.
Note that these photoreceptors only measure brightness and not color, so to get color you either have to place an alternating grid of filters over the sensor, or you have three sensors (one each for red, green, and blue) and a prism that splits light out to all three.
Noise comes from two causes, but the primary cause is photons aren't the only thing that can increase the charge held in each photoreceptor cell. Heat can randomly increase the amount of charge by just a tiny little bit. In direct sunlight this isn't too much of a problem since there are a lot of photos hitting the sensor and they tend to overwhelm the noise.
Low-light is where the noise becomes apparent -- there are fewer photons hitting the sensor so the charge amounts are run through an amplifier (so the generated image will be of the proper brightness) which also amplifies the effect of the random charge noise introduced by heat. The greater the amplification of the charge signal from the sensor, the greater the noise. This is why the more sensitive ISO settings on a DSLR camera are grainy. It's the same effect.
The other thing that causes video noise is the photons themselves. Photons bounce around willy-nilly so the number of photons will vary slightly between photoreceptors and between frames for the same photoreceptor. This accounts for some of the low-level noise you see in a daylight video shot. Once again, in low light the amplification applied to the signal from the sensor will also amplify the slight photon variations into larger variations.
The same thing happens in video filters. If you have an image or video with a little grain and increase the brightness or contrast it will amplify all the little variations and result in more visible noise. The reverse is also true: reducing brightness or contrast will lessen the noise. If you can overexpose your video (without blowing out your highlights) and then darken the exposure in post, that will reduce some of the visible noise. Note that this only works if you increase your exposure by altering your aperature or shutter speed. If your video camera brightens the exposure by simply amplifying the sensor signal (this is how cheaper cameras do it) then you'll gain nothing since the overexposure will introduce more noise from the start.
As for why you see different amounts of noise in different colors -- this might be due to variations in the physics of the sensor itself, but the main reason is because of how the human eye works. The eye is more sensitive to brightness than color, and is more sensitive to reds and greens than blues. Highly-saturated colors are bright, so your eye will pick out noise variations more easily than in darker colors.
The Solution:
Aside from only shooting in bright light (eg. daylight or a fancy lighting setup), I've only found one program that successfully combats video noise acceptably: NeatVideo. I've been a user of their still-image noise removal program, NeatImage, for years but I just recently purchased their video filter and it works beautifully.
The best way to use this program is to get a grey card (or just film a blank, solid area) out of focus (so the only thing the camera sees is noise and not details) at the same camera and light settings your scene will be (or was) shot in. NeatVideo analyzes the noise and can then filter it out of the video with a pretty staggering degree of success. It also has an "advanced" mode that lets you adjust how much filtering to do at different noise levels and lets you separately control how much filtering is applied to the brightness and color channels.
You can remove noise from existing video without shooting a solid out-of-focus shot as described above so long as there is a solid area in at least a single frame of video that you can select to tell NeatVideo "this is supposed to be a solid color, so analyze this part of the frame and treat all variations as 'noise'". This calibration can then be applied to the entire video clip.
It's an easy tool to use and if you only need to work with standard-def video, the Home version only costs $99. (I work with higher-resolution footage and so sprung for the $199 Pro version. Worth every penny.)
Examples:
(click the image for the non-cropped full HD frame)
Original:
NeatVideo noise reduction:
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Thanks for the thorough explanation
-So its basically best to have the gain/ISO higher? How do I know how high my gain/ISO is? (cause I read some people said that it varies, but I have no idea on what).
-So if I reconstruct your sentence a bit... The lower the ISO, the more light you need, but less "noisey" the image will be?
-How about if I have my ISO set pretty high, and still add more lighting, will the grains be removed?..
-Oh on the side note, what is f 2,8...f 5 ...etc etc. ? not sure what that really means. shutter speed?
Its usually best to have your ISO as low as ur lighting conditions will allow.
Yes, lower ISO will lessen noise.
If you set your ISO high and have a lot of light, your noise will be less but the image quality wont be as good if you didnt have the extra light and just kept your ISO lower.
F 2.8, f5 relates to aperture. Values like 1/48, 1/60 etc relate to shuuter speed. There is a lot of information about aperture and shutter speed in older threads. Use the search function and you'll get those basic answers much quicker.
@Escher - great explanation. And the example shows just how greatly it works!! I read about "NeatVideo" but shouldnt this be considered as a last resort? I mean.. no offense and all, but doesnt the first option (brighter lighting, then reduce brightness in post-production) work better? OR better yet, why not use both? First bright lighting and then whats left of noise (if any), you get rid of it with "NeatVideo" . Is that best? ...ok, but tell me what was the most common solution people used before "NeatVideo" came to life??
@Ernest - so lower gain/ISO is the most common setting and most optimal for the best results? AND how do I check how much gain/ISO im using??
. Is that best? ...ok, but tell me what was the most common solution people used before "NeatVideo" came to life?? @Ernest - so lower gain/ISO is the most common setting and most optimal for the best results? AND how do I check how much gain/ISO im using??
In film photography (and the same applies here) for a very sharp, crystal clear, no grain image you shoot very low ISO (like 100 or 64 or even less), and light the subject up well. Higher ISO (like the consumer standard 400) is more versatile as far as lighting conditions, but isn't as sharp, and will show some grain. When you get over 400 you're shooting low light conditions, and just accept (or even want for stylistic reasons) that the image will be grainy.
These guys have done a great job explaining for sure, but in answer to your exact question:
ISO is a term coming from film, and is a basic measurement of film's sensitivity to light. ISO is an international standard (America used to use ASA) comes from the International Organization for Standardization.
When you buy film, you buy an ISO. The lower the number, the less sensitive it is to light and so you need more light to imprint the picture on it.
In the digital world, we don't use film (obviously haha). You do set you camera though and the companies have figured out how to adjust the sensors so that if you set your camera to 200 ISO, using an aperture of f/2.2 it would look the same as 200 ISO speed film exposed through a lens with an aperture of 2.2.
Now onto gain. From wikipedia: "gain is a measure of the ability of a circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output." Basically, you're electronically boosting a signal so that darker areas become light. Just like in Audio, when you increase the gain you increase noise. Some older analog video cameras actually offered Negative gain, which could decrease noise and darken the image.
Ideally, set your ISO at a low speed and light it up well (or open your aperture to let more light in), and don't use any gain.
ISO is a term coming from film, and is a basic measurement of film's sensitivity to light. ISO is an international standard (America used to use ASA) comes from the International Organization for Standardization.
When you buy film, you buy an ISO. The lower the number, the less sensitive it is to light and so you need more light to imprint the picture on it.
In the digital world, we don't use film (obviously haha). You do set you camera though and the companies have figured out how to adjust the sensors so that if you set your camera to 200 ISO, using an aperture of f/2.2 it would look the same as 200 ISO speed film exposed through a lens with an aperture of 2.2.
Now onto gain. From wikipedia: "gain is a measure of the ability of a circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output." Basically, you're electronically boosting a signal so that darker areas become light. Just like in Audio, when you increase the gain you increase noise. Some older analog video cameras actually offered Negative gain, which could decrease noise and darken the image.
Ideally, set your ISO at a low speed and light it up well (or open your aperture to let more light in), and don't use any gain.
Same thing for video. Short Answer, for maximum clarity you want low ISO, probably 200 or 250 max.
Photography 101
It's a choice between three things:
Aperture
Film ISO
Shutter speed
All three affect the amont of light that reaches the film (or sensor). Say I had a shot lit so that the following exposes the shot perfectly
Aperture F 2.8
ISO 200
Shuttter speed 1/50 (the standard shutter speed for 24 FPS video)
The shot would still be exposed perfectly if I
Open up the Aperture to 1.4
Reduce the ISO to 100
Keep the shutter speed the same
The shot would also still be perfectly exposed if I
Close the aperture to 3.5
Leave the ISO at 200
Increase the Shutter speed to 1/125
For everything that that decreases the light one stop, you have to increase it one stop somewhere else. The interplay beween these three is the "art" of photography.
Photography 101
It's a choice between three things:
Aperture
Film ISO
Shutter speed
All three affect the amont of light that reaches the film (or sensor). Say I had a shot lit so that the following exposes the shot perfectly
Aperture F 2.8
ISO 200
Shuttter speed 1/50 (the standard shutter speed for 24 FPS video)
The shot would still be exposed perfectly if I
Open up the Aperture to 1.4
Reduce the ISO to 100
Keep the shutter speed the same
The shot would also still be perfectly exposed if I
Close the aperture to 3.5
Leave the ISO at 200
Increase the Shutter speed to 1/125
For everything that that decreases the light one stop, you have to increase it one stop somewhere else. The interplay beween these three is the "art" of photography.
Thanks a million!
Ok, just so were on the clear, I dont do photography much, those pics I took are just examples for lighting. I suppose everything you said, also goes for shooting videos. Yeah I dont know if I those options. My camera is a SONY DCR-SR57 Handycam. So if anyone has one of those, feel free ..
Ok, just so were on the clear, I dont do photography much, those pics I took are just examples for lighting. I suppose everything you said, also goes for shooting videos.
Yeah I dont know if I those options. My camera is a SONY DCR-SR57 Handycam. So if anyone has one of those, feel free .. Google seqarch didn't turn up much. bust out the manual, and see if it has a "manual" mode. If you have "gain" turn it down.
Yes, absolutely. Always work with the cleanest input image you can generate. That being said, you can't always get optimal lighting and NeatVideo is a tool that lets you handle those situations.
I'm going to be shooting a short film this weekend lit entirely by candlelight. The whole purpose of this is a Worst Case Scenario experiment. I'm going to shoot in the worst conditions I can come up with to learn how to best deal with the kinds of problems that can crop up in a shoot. For a real project it's best to use real lighting.
OR better yet, why not use both? First bright lighting and then whats left of noise (if any), you get rid of it with "NeatVideo"
It's best only if the noise/grain is causing problems in post or is visually distracting. The fewer changes you make to an image, the less quality you lose.
but tell me what was the most common solution people used before "NeatVideo" came to life??
I have no idea. You'll find a lot of indie films from that period of time either have distracting noise or are visibly blurry with weird sharpening artifacts -- you'd blur the image to get rid of the grain, then sharpen to try to bring back edge detail. It was a... non-optimal solution.
Yes, always use the lowest-number ISO setting you can get away with. You will get a much cleaner, sharper image. As far as to your gain/ISO settings, those are going to be dependent on what camera you're using. My Canon 7D is the first video equipment I've ever owned that let you set the ISO directly. All my cameras before that had an "exposure" setting that basically set the sensor signal amplification directly but you'd get no numerical feedback.
I've found that working with the shutter/aperature/ISO combination of settings is the easiest way to get consistent and good results and I'll be happier when more video cameras work this way. If your camera doesn't have this ability then the rule is: Use as much light as possible.
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@Gonzo - man my camera is weird..gotta switch it up soon (I was thinking of Canon XL2 -but first the money lol). I dont think it has manual. I only noticed something called "AUTO SLW SHTTER" which probably meant AUTO SLOW SHUTTER (which is turned on). And I reviewed that my shutter speed can go from 1/3 - 1/3500. But I have NO IDEA how to change it. :S . Not sure where to find "Manual" - checked everything. Atleast I think I have.
@Escher - *thumbs up*.. Yeah, more work for me Oh well, better challenge myself lol. Now building myself some good lighting kits - the stronger the better. Btw, hope that short works out for ya. Let us see it when youre done. I also cant wait to get started on mine. Thanks a million man .
@Escher - *thumbs up*.
. Yeah, more work for me Oh well, better challenge myself lol. Now building myself some good lighting kits - the stronger the better. Btw, hope that short works out for ya. Let us see it when youre done. I also cant wait to get started on mine. Thanks a million man .
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What model camera do you have? A lot of the cheaper ones don't give you much in the way of manual control, and I too learned the painful way just how limiting that is.
Woops, you already listed your camera model. It's a handycam, so I'm not too hopeful.
I have a SONY dcr-sr57 handycam.
Yeah, I know what you mean - this one cost me about 380 € (about 500 dollars) a year back when I bought it. Now its cheaper (about a 100 € cheaper). Oh yeah, so limiting 
. Just cant wait to grab onto a Canon XL2 . When I earn the money ofcourse. Hopefully this one should have MANUAL controls haha.