Grainy low-light performance even after cell phone light trick
I've noticed that when shooting in low light even when locking my exposure and ensuring that I'm at f1.8 with 0db gain using the cell phone light trick, there is some pretty nasty grain visible. I haven't shot more than 5 hours worth of footage so far, but could it be because of the heads need cleaned?
The HV, like many other cameras in this price range and sensor size, is simply not a very good low-light performer. Dirty heads cause dropouts, not grain. There are tricks you can use to simulate shooting in low-light conditions (ND filters, small apertures, etc.), but to shoot in actual low-light is to push the camera into its weakness.
Can't be the heads...
Hv's don't do well in low light -- they aren't as good as a 3ccd camera in this sitution.
THrow some light on it, it won't take much to make it look better. Even a flashlight.
dleo
http://www.neatvideo.com/Originally Posted by CBREEZEHIMSELF
That doesn't make sense. (and no, dirty head could cause dropouts but not grain)
If you properly set up for no gain (0db) there should not be heavy grain visible. The image may be too dark if there is not enough light, (the HV's sensor is ok, but not great, in low light) but you shouldn't get grain.
Best guess is that you did not get 0 gain (there is no direct indication for gain in the hv20 so it must be confirmed by adjusting locked exposure and noticing what (or what does not) changes.)
Last edited by IndyFX; 2008 October 6th at 20:21.
You probably didn't do the trick in a right way. What I did to ensure low light is,
- place a light source in front of the lens. Keep checking the exposure by half pressing the photo button
- monitor the aperture values to go from 1.8 and start to increase
- slowly remove the light source away from the lens.
- aperture starting to drop. Lock it when it first hit F1.8.
This way the bright light tricks the camera to think there're enough light around. So the automatic gain will not kick in.
i really dont understand, why does the gain have to kick in at a certain point? is this deliberately done just to fulfil the fact this is a 'consumer' camcorder?
wont the firmware hack be able to adjust the gain in whatever situation?
Basically, Likeable, once you hit your maximum aperture of f/1.8, the only way the camera can make the picture brighter is by adding gain. This works just like turning up the gain on an audio amplifier, in other words, it amplifies unwanted noise along with the desired signal. A little gain can be a good thing, but the camera will add lots if you let it, making your picture very noisy/grainy.
Canon didn't give us direct control over either the HV20's built-in ND filter or the gain, but with a mini-SD card, a light source and a bit of trial and error, it's possible to lock your exposure and ensure you aren't adding gain even at wide open aperture. I haven't been following the firmware hack thread recently, but I'd be somewhat surprised if it could offer fully independent control of gain, since the camera doesn't offer menu settings or other means of directly adjusting gain.
What Erik said
This clip really shows just how clear and sharp (and grain free) the HV can be (when properly set up) in very low light .
Like a lot of things, low light just requires the correct setup and techniques.
http://www.vimeo.com/713618
Last edited by IndyFX; 2008 October 8th at 22:32. Reason: <sp>
I'm going to see if I can get some test footage up in the next couple days. When setting up for low light, I place a bright light in front of the camera, unlock exposure, then re-lock it. Then I find the first value of f1.8 to shoot with.
I tried a shot where I held a flashlight up to my face right in front of the camera. Looked great. Clear, great contrast on my face and everything behind me was crushed black with no grain at all. Then I did a shot with moderate lighting throughout, setting up exactly the same, and this is where I noticed the grain. It seemed to be mostly on the midtones.
Sounds like the exposure (and gain) is changing, the grain should be no different (if the exposure is locked)
Hint: let the blacks be black, you can't pump up under-lit objects and have no gain grain. Set exposure for the lit objects (0 gain) and let the rest be black (you have 2 choices, black or grainy)
Also be aware 24p mode seems much better at low light (to my eye anyway I have not conducted any specific tests)
The HV20/30 has good (low) grain at 0db gain, if you are seeing grain you are not properly locked at 0db.
You can see in the example clip I gave (not mine BTW) even a couple candles can provide enough illumination (though at very close range) Remember that light follows the inverse square rule, meaning that when you double the distance from the source you quarter the amount of light falling on the object. Quadruple the distance (4X) and you get 1/16 the amount of light. (dam that physics;-)
P.S. Just a thought I don't use it much but I recall a thread where they claimed that spotlight (exposure) mode guarantees 0db gain (even unlocked) so also give that a try in your tests to confirm that you are indeed getting the camera locked to no gain (grain should be the same)
(it would be a godsend to have the amount of gain at least displayed, but it is what it is)
Last edited by IndyFX; 2008 October 9th at 10:50. Reason: Post script
Congratulations folks! It's been 1.5 years since this issue first came up and still no definitive, comprehensible, teachable and learnable system for resolving this issue. I was going to get other stuff done before tackling this but you leave me no choice. I'll go nuts unless I do it now. Thanks
THe camera is trying to expose for the dark. Throwing off the all the internal presets and causing grain.
In these conditions turn the camera on pointed at a light, and adjust carefully.
THis has worked in the past for me, and it works great with the HV20.
GL2 did this sometimes too.
Dleo
CELL PHONE who are we tricking?
Z,Congratulations folks! It's been 1.5 years since this issue first came up and still no definitive, comprehensible, teachable and learnable system for resolving this issue. I was going to get other stuff done before tackling this but you leave me no choice. I'll go nuts unless I do it now. Thanks
I was wondering if you've had a chance to put something together?
tv
Me too, me too!What Erik said
This clip really shows just how clear and sharp (and grain free) the HV can be (when properly set up) in very low light .
Like a lot of things, low light just requires the correct setup and techniques.
http://www.vimeo.com/713618
[ame="http://www.vimeo.com/2539698"]Low-Light Test 4 on Vimeo[/ame]
Scott
Low light + Spotlight mode = 0dB gain
Low light + cinemode = 12dB gain
No grain at 0dB, very little at 12dB (but usefully brighter!). Both modes have other effects of course and are not a "solution", but they're a quick way of proving that the HV20 can avoid grain in low light.
Cheers,
David.
As an aside; who afraid of gain? In that, I should also say grain. Although this applies less to our crappy HV resolution, digital tech. has for a long while been too sterile for some, hence 'dust and scratches' and 'film grain' filters which try in vain to introduce 'character', or a vintage look to footage.
Can you recall the shots in Mann's Miami Vice where the fast boats are heading upriver? Check out the gain from Thomson Grass Valley Viper there.
Yes, as far as video is concerned the higher the res. for our dollar the better.
But for stills I like my Canon 5D because it makes me work hard to get great images. The 5D is crappy enough that the image quality is somewhere between 'filmic' and sterile digital.
Not a whole lot of love for gain here, bro.
Film grain is nice yes, but gain is lame.
Gain means amplification. Are you saying that amplification is lame?
the correct term really if u are talking visually is GRAIN
Actually, the correct term is NOISE.
Gain amplifies noise which causes video grain which is not quite as pleasing as film grain. Yes...Miami Vice had grain all over the place....but i actually liked that grainy look. There are some places where I bet they added grain in post.
Anyways...I think the OP's problem is he did it wrong. I'm willing to bet (though I'm not a betting man) that he had his cam in TV mode...did the trick the wrong way..and is looking at the many f1.8 settings TV mode can show...where all but one of them is actually adding gain to the image....which resulted in the noise he continuously sees.
No one can read the Gospels without feeling the actual presence of Jesus. His personality pulsates in every word. No myth is filled with such life...Albert Einstein
Yes, Ian I agree (on all counts), no doubt a good analogy (between film grain and sensor grain) is the difference in grain between tube (guitar) amps and transistor ones. Tube amps create a grain that is pleasing (to the ear) while transistor amps do not (at least not naturally, some use modified input stages to attempt to mimic the smooth organic sound of tube distortion (grain) But even to this day nothing can beat the sound of a good tube amp)
Could be a stupid question but can damage to the sensor from being exposed to the sun etc be a cause of grain/gain/noise?
Cant believe I mispelled my own name...edWard hobson
I think I've successfully done the cell phone trick. If not, I have to be close....
I'm attaching 2 pictures, a before and after screen capture. The first obviously has some serious gain...ugly. The second is light years better, but still seems grainy to me to some extent. Do I still have some gain filtering in here (i.e. not completely successful at the cell phone trick yet), or is this as good as it gets and I've hit the limits of this cam?
I'm just now diving into the realm of the HV30, and I haven't even purchased a "real" video editor yet. I'm using Vista's version of MovieMaker until I can research which video editor is right for me. Maybe MovieMaker is reducing the quality of my video behind the scenes, hence making it look grainy when there should be none? I've downloaded Corel's trail version of their video editing software to see if that helps, but haven't tried it yet.
Any ideas?
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