The Importance of Focal Length over MP in camera selection

wittaj

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At the urging of several folks here, I created a thread to show the importance of focal length and how focal length can be more important than megapixels (MP).

I mentioned some of this in the post regarding The Hookup’s latest video demonstrating different cameras, including one sold from a forum favorite here @EMPIRETECANDY , but this post will put it all in one place where we can point a NOOB to. The cameras I am highlighting were purchased from @EMPIRETECANDY

Almost every big box store, consumer grade cameras and all-in-one-box kits come with either 2.8mm or 3.6mm cameras. I started with the four 2.8mm camera box kit system and I was like "I can place one on each corner of the house and see my whole property and the whole neighborhood." A newbie loves the wide angle "I can see the whole neighborhood" of the 2.8mm fixed wide angle lens. I LOVED IT WHEN I PUT IT UP. I could see everything that would be blocked looking out the windows.

It is easy to get lured in to thinking the wide angle "see the whole neighborhood" because you are watching it and you see a neighbor go by and you are like "Look at that I can tell that is Heather out walking." and "Yeah I can tell our neighbor 4 down just passed by". Or you watch back the video of you walking around and are like "yeah I can tell that is me".

Little do we realize how much WE can identify a known person just by hair style, clothing, walking pace, gait, etc.

Then one day the door checker comes by. Total stranger. Totally useless video other than what time the door checking happened.

Then you realize that this wide-angle see the whole neighborhood comes at a cost and that cost is not being able to IDENTIFY who did it. These 2.8mm wide angle cameras are great overview cameras or to IDENTIFY someone within 10 feet of the camera. At 40 feet out you need a different camera.

I am going to demonstrate the limitations of thinking the 2.8 or 3.6mm camera is the ideal camera for every situation. Here is my neighborhood, and it is like most neighborhoods – ¼-1/2 acre lot subdivision we can find in anytown USA. No street lights, just house, porch, and lamp post lighting. But a 2.8mm camera on each corner of the house lets me see my whole property, so let's see how it does with trying to IDENTIFY someone on the public sidewalk.

1648519363146.png

Here is my next door neighbor out for his usual 11pm jog. The distance is 90 feet (I blacked out most of the wide angle image to help focus the eyes to the person) I chose this clip because he is jogging (and said I could use him LOL), and this demonstrates how you can capture clear images of motion at night instead of the blurry images we often see from big box store cameras or even the examples The Hookup and other YouTuber's shows in their videos (clearly not dialed in and probably on default/auto settings).

I will preface this with I do not have enough light to run these cameras in color, so I had to force them into color and spent a lot of time tweaking each parameter to get the most out of it in color. I am running right at the brink of it going to crappy motion blur/ghosting and running higher parameters than we would recommend. I can get crisper images in B/W with infrared and do run a few cams that way, but I prefer color if possible.

This is from my 5442-ZE set to 3.6mm. This is a 4MP camera that many consider king of the hill. It gives me a great overview of my entire front yard. I can tell that is my neighbor. But at 90 feet you are not going to IDENTIFY. But when someone gets withing 10-15 feet, it is then the right camera for IDENTIFY. You can see there is no motion blur, but there is blur due to the distance. But this would be useless to identify a stranger, but I can tell it is my neighbor.

1648518680170.png


But then people think we can digital zoom, so let’s do that.

1648518721046.png


Nope, doesn’t work, especially at night. A pixelated mess as the program tries to fill in missing pieces as you digital zoom. If you want to see things far away, you need optical zoom, digital zoom only works in the movies and TV...And the optical zoom is done real time - for a varifocal it is a set it and forget it. You cannot go to recorded video and optically zoom in later, at that point it is digital zoom, and the sensors on these cameras are so small which is why digital zoom doesn't work very well after the fact.

Only on TV and in the movies do we see this kind of digital zoom and clean images LOL:

1652027588538.png

So how do we get clean captures at longer distances….well that would be with more focal length. Which means a different camera.

Here is an image taken within seconds of the image above, except this time it is with the 5241E-Z12E varifocal with an optical range from 5.3mm to 64mm. This is a 2MP camera. At this distance, the focal length is set to about 54mm.

1648518969047.png

Notice that this is at night, in color, with basically no blur of a person running. This image could be used by the police to identify a person (the .bmp files are clearer but also larger in size, so I opted for a smaller file size that still gets the point across).

So yes, one can obtain images at night that are not a blur. It comes down to having a camera that allows the user to set parameters (and the camera adheres to), dialing in of the camera to the field of view, and the proper focal length for the distance to be covered.
 
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wittaj

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Regarding camera selections, the distance to be covered from the camera to the object location is the most important factor and more important than MP.

You need to identify the areas you want to cover and pick a camera designed to cover that distance. In some instances, it may be a 2MP or 4MP that is the right camera and not an 8MP. DO NOT CHASE MP!!!

It is why we recommend to purchase one good varifocal and test it at all the proposed locations day and night to figure out the correct focal lengths and cams.

A few other tips....It is simple LOL do not chase MP - do not buy a 4MP camera that is anything smaller than a 1/1.8" sensor. Do not buy a 2MP camera that is anything smaller than a 1/2.8" sensor. Do not buy a 4K (8MP) camera on anything smaller than a 1/1.2" sensor. Unfortunately, most 4k (8MP) cams are on the same sensor as a 2MP and thus the 2MP will kick its butt all night long as the 4k will need 4 times the light than the 2MP... 4k will do very poor at night unless you have stadium quality lighting (well a lot of lighting LOL).


Here are my general distance recommendations, but switch out the Dahua 5442 series camera to the equivalent 2MP on the 1/2.8" sensor or equivalent Hikvision works as well.
  • 5442 fixed lens 2.8mm or the 4K/X - anything within 10 feet of camera OR as an overview camera
  • T5449H-ASE-D2 2.8mm fixed lens - anything within 10 feet of camera where the object would be in a backlit condition at night
  • 5441F-AS-E2 (AKA Boobie cam) or E3241F-AS-M- great choice for a front door camera. The boobie cam can have one lens pointed down for packages
  • T5241H-AS-PV - Great little active deterrence camera with two way talk. Good for anything within 10 feet of camera or as an overview camera
  • 5442 ZE or 5842-ZE- varifocal up to 13mm- distances up to 40-50 feet (personally I wouldn't go past the 30 foot range but I like things closer)
  • 5442 Z4E - varifocal up to 32mm - anything up to 80-100 feet (personally I wouldn't go past 60 feet but I like things closer)
  • 5241-Z12E - varifocal up to 64mm - anything from 80 feet to almost 200 feet (personally I wouldn't go past 150 feet because I like things closer)
  • 5241-Z12E - for a license plate cam that you would angle up the street to get plates up to about 175 feet away, or up to 220 with additional IR.
  • 49225 PTZ - great auto-track PTZ and in conjunction with an NVR or Blue Iris and the cameras above that you can use as spotter cams to point the PTZ to the correct location to compliment the fixed cams.

You need to get the correct camera for the area trying to be covered. A wide angle 2.8mm to IDENTIFY someone 40 feet away is the wrong camera regardless of how good the camera is. A 2.8mm camera to IDENTIFY someone within 10 feet is a good choice OR it is an overview camera to see something happened but not be able to identify who.

One camera cannot be the be all, see all. Each one is selected for covering a specific area. Most of us here have different brands and types, from fixed cams, to varifocals, to PTZs, each one selected for it's primary purpose and to utilize the strength of that particular camera.

So you will need to identify the distance the camera would be from the activities you want to IDENTIFY on and purchase the correct camera for that distance as an optical zoom.

If you want to see things far away, you need optical zoom, digital zoom only works in the movies and TV...And the optical zoom is done real time - for a varifocal it is a set it and forget it. You cannot go to recorded video and optically zoom in later, at that point it is digital zoom, and the sensors on these cameras are so small which is why digital zoom doesn't work very well after the fact.

This image shows the importance of understanding focal length and its role in DORI (Detect, Observe, Recognize, Identify) and how one camera cannot do it all. If you want to IDENTIFY in the DOR part, then you need a camera with optical zoom to that location.

1655006174184.png
 
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samplenhold

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One camera cannot be the be all, see all. Each one is selected for covering a specific area. Most of us here have different brands and types, from fixed cams, to varifocals, to PTZs, each one selected for it's primary purpose and to utilize the strength of that particular camera.
Love this one! I have said this on so many threads.

Thank you for putting this together. Hopefully people here will link to this in answer to specific threads when needed. I have bookmarked it to do just that.
 

NightLife

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One day, eventually, we will all likely have to direct our significant others to this thread. Ideally a week before the courier drops off our nth camera...:D


Personally speaking, my 'n' may be a big fat "2"! As I walked downstairs today I spied my new camera sitting on the floor in the entrance way. I blurted out 'Wow, it's here early!'.

...to which my loving wife replied .. 'Yeah, what's that for?'. :screwy:

I literally spun a 180 on my heels, and marched back upstairs to begin the sell. "Remember those black wolves you spotted out on the lake 24 hrs ago? Well, instead on them being completely indistinguishable even with the binoculars, they're going to look like they're sitting on our front lawn!

My work is cut out.
 

jrbeddow

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Like tools, fishing gear, guns, and other guy-type stuff, once you have enough of it they stop noticing the new ones. Kind of like shoes and purses on the other side. ; )
True, except for the actual deliveries, when sometimes a bit'o-splainin' might be called out by the SO (aka the CFO).
 

wittaj

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I thought I would link to this thread the little experiment I did with different resolutions for LPR. While it was specific to LPR, many of the same takeaways can work with non-LPR as well.

As I said in the thread, I was shocked that OpenALPR could read a plate with D1 resolution. Shows that chasing MP isn't always the answer. If the MP/sensor ratio is ideal, one can get away with a lower resolution.

 

mattp

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At the urging of several folks here, I created a thread to show the importance of focal length and how focal length can be more important than megapixels (MP).

I mentioned some of this in the post regarding The Hookup’s latest video demonstrating different cameras, including one sold from a forum favorite here @EMPIRETECANDY , but this post will put it all in one place where we can point a NOOB to. The cameras I am highlighting were purchased from @EMPIRETECANDY

Almost every big box store, consumer grade cameras and all-in-one-box kits come with either 2.8mm or 3.6mm cameras. I started with the four 2.8mm camera box kit system and I was like "I can place one on each corner of the house and see my whole property and the whole neighborhood." A newbie loves the wide angle "I can see the whole neighborhood" of the 2.8mm fixed wide angle lens. I LOVED IT WHEN I PUT IT UP. I could see everything that would be blocked looking out the windows.

It is easy to get lured in to thinking the wide angle "see the whole neighborhood" because you are watching it and you see a neighbor go by and you are like "Look at that I can tell that is Heather out walking." and "Yeah I can tell our neighbor 4 down just passed by". Or you watch back the video of you walking around and are like "yeah I can tell that is me".

Little do we realize how much WE can identify a known person just by hair style, clothing, walking pace, gait, etc.

Then one day the door checker comes by. Total stranger. Totally useless video other than what time the door checking happened.

Then you realize that this wide-angle see the whole neighborhood comes at a cost and that cost is not being able to IDENTIFY who did it. These 2.8mm wide angle cameras are great overview cameras or to IDENTIFY someone within 10 feet of the camera. At 40 feet out you need a different camera.

I am going to demonstrate the limitations of thinking the 2.8 or 3.6mm camera is the ideal camera for every situation. Here is my neighborhood, and it is like most neighborhoods – ¼-1/2 acre lot subdivision we can find in anytown USA. No street lights, just house, porch, and lamp post lighting. But a 2.8mm camera on each corner of the house lets me see my whole property, so let's see how it does with trying to IDENTIFY someone on the public sidewalk.

View attachment 123580

Here is my next door neighbor out for his usual 11pm jog. The distance is 90 feet (I blacked out most of the wide angle image to help focus the eyes to the person) I chose this clip because he is jogging (and said I could use him LOL), and this demonstrates how you can capture clear images of motion at night instead of the blurry images we often see from big box store cameras or even the examples The Hookup and other YouTuber's shows in their videos (clearly not dialed in and probably on default/auto settings).

I will preface this with I do not have enough light to run these cameras in color, so I had to force them into color and spent a lot of time tweaking each parameter to get the most out of it in color. I am running right at the brink of it going to crappy motion blur/ghosting and running higher parameters than we would recommend. I can get crisper images in B/W with infrared and do run a few cams that way, but I prefer color if possible.

This is from my 5442-ZE set to 3.6mm. This is a 4MP camera that many consider king of the hill. It gives me a great overview of my entire front yard. I can tell that is my neighbor. But at 90 feet you are not going to IDENTIFY. But when someone gets withing 10-15 feet, it is then the right camera for IDENTIFY. You can see there is no motion blur, but there is blur due to the distance. But this would be useless to identify a stranger.

View attachment 123576


But then people think we can digital zoom, so let’s do that.

View attachment 123577


Nope, doesn’t work, especially at night. A pixelated mess as the program tries to fill in missing pieces as you digital zoom. If you want to see things far away, you need optical zoom, digital zoom only works in the movies and TV...And the optical zoom is done real time - for a varifocal it is a set it and forget it. You cannot go to recorded video and optically zoom in later, at that point it is digital zoom, and the sensors on these cameras are so small which is why digital zoom doesn't work very well after the fact.

So how do we get clean captures at longer distances….well that would be with more focal length. Which means a different camera.

Here is an image taken within seconds of the image above, except this time it is with the 5241E-Z12E varifocal with an optical range from 5.3mm to 64mm. This is a 2MP camera. At this distance, the focal length is set to about 54mm.

View attachment 123579

Notice that this is at night, in color, with basically no blur. This image could be used by the police to identify a person (the .bmp files are clearer but also larger in size, so I opted for a smaller file size that still gets the point across).

So yes, one can obtain images at night that are not a blur. It comes down to having a camera that allows the user to set parameters (and the camera adheres to), dialing in of the camera to the field of view, and the proper focal length for the distance to be covered.
Hey @wittaj,
Do you have the full picture to see an area that this camera can cover?
1648685120143.png
I guess what I'm asking is at 54mm zoom what is the degrees the camera covers. I'm guessing something like 60 degrees?
Is there a chart somewhere that converts mm zoom to degrees?

In the last couple of days you have posted some really good information regarding low light cameras, focal length, MP, sensor size, etc. Thank you for educating us.
 

wittaj

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Yeah, that camera would be about 60 degrees pulled all the way out. At this zoom, it is about 14 degrees or so. Not zoomed in at all, this camera would be roughly half the view of a 3.6mm camera.

But you would never use this camera at the smaller focal lengths, you would use a different camera.

That is the biggest aspect that people need to recognize that the 2.8mm focal length gives you a wide-angle view, but that comes at a cost of not being able to IDENTIFY at distance.

As the focal length gets larger, the field of view gets smaller. This allows you to IDENTIFY, but it comes at the expense of not being able to see a wide area.

That is why it is best to utilize a combination of different cameras and focal lengths - wide angle to see everything, zoomed in cameras to pinch points, to possibly complimenting the coverage with a PTZ that uses a fixed cam to spin the PTZ to the area of interest.

This is a pretty good website at being able to pull your house up and select cameras and get an idea of how wide you can see. However, I wouldn't go by the representative sample image for anything much beyond 30 feet.

 

mattp

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@sebastiantombs
wheres your rifle bullet caliber/ sensor size posting?
thats a keeper too. Wiki-able
These guys have been on a roll the past couple of days with some really good information.
Here's that link you were looking for:

It's good you remembered who posted it. I've used the search to find similar postings recently, and it worked to find the link above:
1648735693757.png
 
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Save you some trouble -
The smaller the lux number the better the low light performance. 0.002 is better than 0.02
The smaller the "F" of the lens the better the low light performance. F1.4 is better than F1.8
The larger the sensor the better the low light performance. 1/1.8" is better (bigger) than 1/2.7"
The higher the megapixels for the same size sensor the worse the low light performance. A 4MP camera with a 1/1.8" sensor will perform better than a 8MP camera with that same 1/1.8" sensor.

720P - 1/3" = .333"
2MP - 1/2.8" = .357" (think a .38 caliber bullet)
4MP - 1/1.8" = .555" (bigger than a .50 caliber bullet or ball)
8MP - 1/1.2" = .833" (bigger than a 20mm chain gun round)
 

wittaj

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So my first post in this thread was trying to identify someone at 90 feet.

Here is a great example of two images taken at the same time (early AM while still dark out) of the same person 60 feet away from just slightly different angles - one from the 5442-ZE 4MP set to 3.6mm that I digitally zoomed to make the person about the same size as the person in the 2MP varifocal optically zoomed.

Compared to Post #1, being 30 feet closer does result in a significant improvement (plus this one is aided by infrared), but the digitally zoomed image still could not be used by police to IDENTIFY.


trash 4MP digital zoom.jpg




trash 2MP optical zoomed.png


In case someone cannot figure it out, the 4MP that is digitally zoomed in is the B&W picture and the 2MP varifocal optically zoomed in is the color picture LOL.

I think most would agree that the optically zoomed 2MP picture beats the digitally zoomed 4MP picture - you can make out details and read some of the signage and make out bolts, etc. that are just a blur on the 4MP, which is being benefited by the same light the 2MP camera is getting plus the IR.
 

wittaj

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Now what about daytime, can you get away with more digital zoom then?

So here are comparable daytime pics taken at the same time (noon) of the same vehicle from just slightly different angles - one from the 5442-ZE 4MP set to 3.6mm that I digitally zoomed to make the vehicle about the same size as the vehicle in the 2MP 5241-Z12E varifocal optically zoomed. You can make out the phone number in the 2MP optically zoomed picture, but not in the 4MP digitally zoomed picture.


FedEx daytime 4MP digital zoom.jpg




FedEx daytime 2MP optical zoom.jpg


As expected, with enough light, the digital zoom is more effective, but it isn't perfect either.

The 2MP camera is 4092 CBR bitrate and the 4MP is 8192 CBR bitrate, which are appropriate for their relative resolutions. Both at H264. H265 is even worse digital zoomed due to how it blocks for compression.

Digital zoom uses an algorithm to achieve that zoom and that also introduces additional noise and artifacts as the algorithm tries to fill in missing pieces and interpolate as the digital zoom gets bigger. It isn't like taking a magnifying glass to a hard copy of something. Digital zoom introduces artifacts not present in the original size.

Economically, the sensor size simply isn't available to us (nor would we want the size of the camera to accommodate it) to provide us with meaningful digital zoom beyond just a little bit.

I tested all of this when I got the camera by digital zooming to something across the street and changing bitrates until I saw a difference - I wanted to try to squeeze as much digital zoom as I could out of it, and the simple fact is you just can't do a lot.

By comparison, the non digitally zoomed 4MP image looks great and something within the DORI number for IDENTIFY looks great. But when you digital zoom, this is what you get, unless you are in a movie or on TV and then you are seeing nose hairs when digital zooming LOL.

There is a trade off with every camera. Do you want a wide field of view but lose details at distance, or a narrow field of view but able to get details at distance.

Most of us have a wide angle fixed camera as an overview to OBSERVE a wider view and can serve to IDENTIFY when a subject is within the DORI distance for that particular camera, supplemented with optical zoomed cameras zoomed in to pinch points or other points of interest further out.

Again, it is why we say one camera cannot do all, be all, see all. A 2.8mm or 3.6mm fixed cam is a great overview camera to get a big wide picture, but it isn't going to be used to IDENTIFY a stranger at 60 feet, especially at night. You need another camera optically zoomed to that area.
 

wittaj

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So whataya Sayin Wittaj? :)
My 2Mp's are still desireable in this day of 8Mp cams?
It depends on the distance to be covered.

At 10-15 feet, the 4K/X or 5442 or 5449 or 5831 will beat the 2MP in most situations due to optimal MP/sensor ratios and close enough for the respective focal length.

At about 40 feet or so, the 5442-Z4E is probably beating the 2MP in most situations.

Beyond 60 feet, unless you go to a PTZ, the 2MP 5241-Z12E is the only fixed cam with the focal length to get those distances.
 
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