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.@Parley Just looking again at your 6mm version and just something not right with the focus on that mate, I didn't like to say TBH. I have a 4mm Dahua in my yard and most of it is in focus close and far.
What an interesting assessment CCTVCam - thanks for that. Unfortunately, though, I don’t completely share some of your detail or your conclusion.My understanding is roughly the above but slightly different.
A sensor records the image as an electronic signal, in other words a photon of light striking the sensor induces an electric field in the sensor which the image processor then turns into a visible picture based on the electronic signal supplied. As Wittaj says, in addition to photons of light producing an electronic signal, you have "noise" which is transient current induced in the sensor by nearby electronic components. These are small electric signals that are much smaller in amplitude than eg the signal from a photon striking the sensor in daylight. As the amount of light reduces, so does the strength of the photon striking the sensor and so the amplitude of the electric current produced is smaller too. There becomes a point in low light where the signal from the photon striking the sensor becomes too weak for the processor to process, so the picture becomes black. In order to get around this or enhance a weak signal, the unit amplifies the signal it receives to make it strong enough to process. This is called the gain. However, the amplification process cannot distinguish between the actual signal and the electronic tranisent signals induced by nearby electric components as a weak signal in low light can have an ampitude not disimilar to that from the background noise of these transients. As a result, both get amplified and processed resulting in rogue pixels as the processor can't distinguish the genuine signal from the amplified background noise due oto their similar amplitude. These rogue pixels are seen in the picture as artefacts because they don't match the colour or shape of nearby pixels and so stand out as "snow". Now I don't completely understand the mechanism of ghosting but at a guess, I'd guess what is happening is the signal of the person who's moving in the picture is so weak due to their movement that the signal is intermittently too weak to be processed. As a result the person has missing pixels where the camera can't process the signal so these appear black. As these change from frame to frame, with pixels in some and not others at certain places in the image, the image takes on a transparent appearance as one frame the pixel is there and the next it's gone, then back etc. As a "video" image is a series of frames per second at a fast rate, if certain frames are missing, the object may adopt a less than solid look. I'm pleased to be corrected if anyone can offer a more accurate explanation.
I believe therefore the antidote to ghosting is to reduce the gain and if the subject can't be seen add more light. Again I defer to those with more experience if they have other successful solutions.
Mmm. Good point wittaj. Maybe these clever Chinese engineers find ways to get the results their bosses demand.@CCTVCam - very well said! It is amazing how much light cameras need. The sensors are small and need light.
I suspect that ghosting is probably present even at lower gains, but they just are not registered or visibly seen until the gain is cranked up.
I have not touched noise reduction and will see ghosting just by cranking up the gain.
And we do not know the algorithms of these cameras - some or all could change the noise algorithm based on a setting and maybe because gain amplifies the noise, the algorithm automatically adjust the NR to a different scale, even if we can control the NR. So a NR at say 30 and gain at 40 may be a different NR scale for a gain at 80 and even though it may show 30 as the NR level because you didn't touch it, you probably have to crank it down as a result of the higher gain?
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.The focus on my 2.8mm and 4mm was good at any range as seen in my last clips. I personally think it has a problem and wait your new clips from when you re position it.
No Offence taken. I don't claim to be an expert. A few thoughts: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.
So they blame a combination of 5 settings - slow shutter speed, high gain, high DNR, high DWDR and smoothing settings.3. Improper Camera Settings
Ghost on CCTV cameras can also be caused by slow shutter speed, high gain, high DNR, high DWDR and smoothing settings.
Taking the noise reduction for example, the higher the noise reduction is, the worse the CCTV camera ghosting effect becomes.
Usually around 35-40 noise reduction is a decent balance between less noise and too much security IP camera ghosting.
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.Yes, I have one.
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.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.
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.(it reads roughly 160kB/s in the General tab of Blue Iris)
As pointed out by others the cam is kbits and bi is bytes.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).