Newbie - 2.1 vs 3 MP

[FreeLunch 0]

Obviously, 3MP has a million more pixels than 2.1 MP. However, is there much difference between the two in practical use? I'm considering this for a typical residential setup.

[varascope 0]

It comes down to focal distance. A 480tvl camera properly placed can identify a face at 10' or less. So 2.1 for longer distances gives you X clarity on zoom. The X is the part that has a more in depth formula.

 

1. If you were watching the local kids in the neighborhood and new who they are then 40% focal length may be enough

2. If it is for identifying an unknown person 80% focal length. The FBI recommends 110%.

3. A camera placed farther away but with a better zoom maybe better than a camera placed closer but too high. You see this from the amateurs that install most convenient store systems. The police end up with more top of the hat than a face.

There is more but you get the general idea

 

Now this is typical recommendations for focal length based on lens zoom. Since IP cameras is mostly fixed length lens, although there are exceptions, the formula then applies to the zoom ratio. I know most poeple are asking the difference between 2.1 vs 3 because of cost differences but each situation is different. If you place one to catch people walking to the door then 2.1 or even 1.3 is more than enough. But if your talking about the house the end of the driveway 3MP maybe more suited. It also depends on the image sensor make and model. Night time requirements also are a factor. For example a 3MP Mobotix looks terrible at night but the new 5MP is significantly better.

 

In any setup, define your objectives first in order of importance then that will narrow down your selection of the right camera.

[buellwinkle 0]

It's not so much about the "one million pixels", it's the aspect ratio assuming you are referring to 1080P for 2MP. For example, imagine you have a camera looking at your driveway. Most suburban 2 car garage driveways are square, say 20 x 20', some more longer than wider and the exception is maybe a condo with a shallow driveway. Given the same lens, having a 16:9 aspect ratio may not capture enough depth relative to width to get the entire depth of the garage as well as a 4:3 aspect ratio.

 

Also, most of the extra million pixels is the height of the image, so someone walking in your driveway would be represented by 50% more pixels allowing you to identify them 50% further away. Most experts agree that you need a person face to be about 85 pixel tall to identify them. To reach that goal say with a 4mm lens and 1/3" sensor, with 1080P, you may be able to reach that goal at say 20' but with 3MP you may reach that goal at 30'.

 

Of course there are equally valid reason for 1080P where capturing more sky or more earth may not give you any value, then having the wide aspect ratio makes more sense. Actually just set a 3MP to 1080P for that same reason as having too much sky at the wrong time of day created lens flare.

 

Having the ability to chose what's best for the circumstances is what makes the most sense. In regards to video, most people have 1080P monitors making anything above that in a video meaningless except for taking snapshots and generally that's what I show the Sheriffs first and if they want more, they usually take the raw video to their crime lab people. On the other hand, 2K monitors (1440P) are become more popular and then you can view your 3MP video at pretty close to full resolution. I see 4K (2160P) TV's and Monitors becoming more affordable later this year. It's like when 3D TV's came out, you paid double for that feature and then within a year or two it was maybe a $100 difference.

[MaxIcon 0]

The other thing to watch for beside aspect ratio is whether the pixels are directly sampled or scaled.

 

Some cams, like Dahua, sample the pixels directly and show the same pixels per foot in either 3MP or 1080P mode, so you won't actually get more detail in pixels per foot, but will get a wider or narrower view.

 

If the camera scales the 2 modes so that one axis or the other shows the same in both modes (it can't be both axes or it will look distorted, due to the different aspect ratios), then you will get better resolution in the 3MP mode.

 

Then there's the Hik 2032, which scales the image such that the 1080P gives a wider FOV than the 3MP mode, so the 3MP will give more pixels per foot, even more so than one that scales both modes for the same FOV.

 

Bottom line: It depends on the camera's firmware, and it's a good thing to verify before buying if this is important.