Hikvision ColorVu + 4K (DS-2CD2087G2-L)
- Thread starter ZeeCam
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ljw2k
Known around here
Parley
Known around here
I am going to relocate it to another more suitable location as soon as the Dahua 5442-Z12 comes out. At that time I will play with it some more.
ljw2k
Known around here
What an interesting assessment CCTVCam - thanks for that. Unfortunately, though, I don’t completely share some of your detail or your conclusion.
1. Clearly, noise changes the voltage presented to the a/d converter and you could argue that if you double the gain, so you double the error. However, the main signal is also doubled. So, with a higher gain the signal available for processing will be stronger and not weaker.
2. Ghosted pixels are not missing and black. They take on the average of nearby frames.
3. The character of ghosting is visually different to that of noise.
4. Ghosting has a characteristic trail. The effect you describe (noise) would be contained within each individual frame. A moving object with ghosting is exhibited simultaneously in separate frames.
5. A faster shutter (although reducing blur) makes the signal to noise ratio even worse.
6. What’s your assessment of ljw2k’s excellent example videos above? Is it your opinion that ghosting is more prominent when he increased the gain from 50% to 100%?
CCTVCam, please don’t be offended by my assessment being at variance with yours. Perhaps my view is far too superficial - there are many other factors and things going on in these cameras that I’m completely ignorant of.
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Mmm. Good point wittaj. Maybe these clever Chinese engineers find ways to get the results their bosses demand.
These cameras are pretty hard to come by in the states.B&H was all I could find. Seemed pricey...does anyone anticipate the turret versions being better and worth waiting for? Is Andy still selling these. Doesn’t seem to have any 
Parley
Known around here
I was just thinking that the tree and wall being so close to the camera might have an effect on it. The new location will not have those problems. We shall see.
ljw2k
Known around here
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For this particular case 2.8mm works good. For me it's useless. I would either capture a bush or a garage door.
CCTVCam
Known around here
- Sep 25, 2017
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No Offence taken. I don't claim to be an expert. A few thoughts:
1. Yes both signals are doubled but the signals will remain close in amplitude after doubling so whilst processable, amplification probably does little to hlep with separation. This is where the noise reduction maybe has issues in deciding between signal and junk.
2. I think you're correct as the software is probably guessing although on a really low light video, a lot of surrounding pixels maybe black / near black.
3. Yes I agree and different to blur. However, there have been videos in other threads where people have appeared hollow. I can't find the thread but I remember a video of someones back garden where a figure walked across and the face / figure disappeared / reappeared almost frame by frame and was translucent most of the time. That suggests to me maybe some data is incorrect / missing on some of the frames.
4. I would agree, a faster shutter reduces the available light so will make the non noise proportion of the signal weaker. However, there's a difference between ghosting and blur. Something is generating a persistence of image between frames. Maybe as compression guesses the change in pixels from 1 frame to a next where the info is missing it's guessing wrongly based on the pixels in the previous frame. I don't know, I'm not a camera or electronics expert.
5. I find it very hard to conclude anything about ljk's videos as I think the light is sufficient to make the effect marginal. I think there maybe some improvement from 1/60 @ 100 gain to 1/60 @ 50 gain. However, 1/175 @ 50 seems to make the picture slightly less sharp and introduces a bit more blur / ghosting! The exact opposite of what you might expect.
I did a bit of googling and came across this, although explanations seem to vary from website to website. It seems the general concensus is it's a mix between gain, shutter and noise reduction.
It seems the general snow you see is something called Shot Noise and is caused by insufficient photons hitting the sensor.
An article on IPVM blames shutter speed. However this looks to me to be more like blur than ghosting:
Camera Slow Shutter / Ghosting Tested
Reolink have an article discussing ghosts and cctv:
What Causes Ghost Images on Security Cameras?
Uncover the truth about What Causes Ghost Images on Security Cameras - explore scientific explanations and learn about the history of ghost hunters and their devices.
reolink.com
This seems closer to an explanation in my opinion. About 1/2 way down the page, this is their conclusion / suggestions:
So they blame a combination of 5 settings - slow shutter speed, high gain, high DNR, high DWDR and smoothing settings.
It would seem that the explanation may lie somewhere between all our conclusions therefore Dave and tweaking those settings relative to each other maybe the solution.
What excellent information CCTVCam! On my side, I would have to confess not to have googled for information - instead just spouting what seems right to me. There’s a string of links, some of which I’ve now read. I think my mental definition of ghosting has been too narrow and when broadened, then many camera settings are seen to contribute. Also, one particularly interesting characteristic I had not considered from the Reolink article was, “As the heat is far less transient than light, it will still remain when the source of heat is removed.”
Thanks again for broadening my understanding. I will be taking delivery later this week of one of the cameras that’s the subject of this thread. It will be far better to “practice instead of profess”, especially in my case. We shall see...
Thanks again for broadening my understanding. I will be taking delivery later this week of one of the cameras that’s the subject of this thread. It will be far better to “practice instead of profess”, especially in my case. We shall see...
Good evening CCTVCam. Relaxing in the armchair this evening after a bottle of red, I’m picking up on your valid comment that ljw2k’s video at 1/175, 50% was less sharp than the one at 1/60, 50%. I have a theory. Could it be that this camera has an auto iris and when fixing the shutter at 1/60, the camera has too much light and needs to close the aperture down, thereby increasing the depth of focus (the distance to the camera is far less than the specified minimum of 7m). However, at 1/175, the available light is reduced and the camera automatically opens the iris fully out to f 1.0. So this time, the Sainsbury’s delivery guy becomes more and more out of focus as he approaches the camera. To support this theory, I would otherwise expect the 1/175 video to be darker.
Just thought of another theory - more in line with our key discussion topic. At 1/175, the noise level increases. So, although not severe, the noise reduction algorithm averages the pixels from previous frames causing blur in a moving person.
It‘s a shame that wopi82 no longer visits this forum. For sure, he would know the actual reason.
A technical footnote that I really would like feedback on is about the brightness of an image. I think wopi82 once pointed out that the perception of light to the eye is logarithmic. Does this mean, for example, when it’s nearly dark and the shutter time is lengthened by 300% (1/175 to 1/60), the eye only perceives a change corresponding to log3 - i.e. is only 50% brighter, even though the signal to noise ratio would be improved by a factor of 3? And, of course, when going the other way, the noise becomes three times worse even though the image is still half as bright. I really struggle with this one.
Just thought of another theory - more in line with our key discussion topic. At 1/175, the noise level increases. So, although not severe, the noise reduction algorithm averages the pixels from previous frames causing blur in a moving person.
It‘s a shame that wopi82 no longer visits this forum. For sure, he would know the actual reason.
A technical footnote that I really would like feedback on is about the brightness of an image. I think wopi82 once pointed out that the perception of light to the eye is logarithmic. Does this mean, for example, when it’s nearly dark and the shutter time is lengthened by 300% (1/175 to 1/60), the eye only perceives a change corresponding to log3 - i.e. is only 50% brighter, even though the signal to noise ratio would be improved by a factor of 3? And, of course, when going the other way, the noise becomes three times worse even though the image is still half as bright. I really struggle with this one.
Hi Parley - I'm looking to buy a DS-2CD2087G2-LU with a 6mm lens. Is this the model and lens option you purchased and if you don't mind me asking where did you purchase it from? I just installed a DS-2CD2087G2-LU yesterday that has a 4mm lens, but I really need a 6mm but I can't seem to find anyone selling it. I've messaged Andy "EMPIRETECANDY" to see if he sells it, just waiting to hear back from him.
Parley
Known around here
I bought it from Andy. It was his last one. I am waiting for him to restock as I want to buy the 4mm version for another location.
I’ve bought the 4mm version of this camera (from ljw2k, it was surplus to his requirements). I’m extremely pleased with it. To get the very best image quality possible, I‘ve used the ‘highest’ Video Quality setting with a constant bit rate of 16,384kbit/s (the maximum). However, with a detailed but static image, the actual main stream bitrate is approx 10 times lower (it reads roughly 160kB/s in the General tab of Blue Iris). It is the same bitrate as this when set to VBR. Is there another parameter in the camera that I’m not aware of that when set prevents CBR or is it a firmware bug?
The bitrate doesn’t seem to increase much when motion is present, when I want as many data bits in the frames as possible. To get the bitrate up to anywhere near 16Mbit, I have to turn the noise reduction completely off at night with a short exposure time.
Has anyone else on the forum checked this out?
I‘m astonished how the image of a 8MP camera can be so good with such a low bitrate, even when the image is static (looks perfect to me). I say this in light of how blotchy the image quality of Dahua’s 5442 family can be with VBR, even though the bitrate only ever falls to roughly 50% of maximum with a static image.
Another small issue that has been mentioned by ljw2k is that the manual LED brightness control does not function and is permanently on maximum (although this is my preferred setting anyway).
The bitrate doesn’t seem to increase much when motion is present, when I want as many data bits in the frames as possible. To get the bitrate up to anywhere near 16Mbit, I have to turn the noise reduction completely off at night with a short exposure time.
Has anyone else on the forum checked this out?
I‘m astonished how the image of a 8MP camera can be so good with such a low bitrate, even when the image is static (looks perfect to me). I say this in light of how blotchy the image quality of Dahua’s 5442 family can be with VBR, even though the bitrate only ever falls to roughly 50% of maximum with a static image.
Another small issue that has been mentioned by ljw2k is that the manual LED brightness control does not function and is permanently on maximum (although this is my preferred setting anyway).
alastairstevenson
Staff member
With the caveat that I'm not a BI user --- that's bytes per second, as opposed to bits per second in the camera bitrate settings.
ljw2k
Known around here
spammenotinoz
Getting comfortable
As pointed out by others the cam is kbits and bi is bytes.
1 bit = 0.125 BytesI don't have this cam, butI also feel the CBR is a targeted bit rate, and with the efficiency of H.265 it often won't reach the target bitrate.
This isn't so much a flaw, but a positive of the high efficiency of compression.
Even with CBR, even at a low 15fps, I am disappointed in my 5442. I get slight ghosting (and no it's not shutter speed). Complete speculation but it's like Dahua skimped out on the CPU and the cam can not keep up with the work when there is a lot of motion.
If I drop to H.264 it improved, but the 5442 wasn't a cheap cam.
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