2.8mm vs 3.6mm, which do you prefer for a fixed-lens?
- Thread starter Arjun
- Start date
I prefer whatever one gets the FOV required for that particular application. It's not a matter of personal preference between one or the other.
Thanks,
What do most installers default to? It seems the field of view varies between 81 degrees and 110 degrees, which is quite significant.
In which locations would the 2.8mm and 3.6mm's be better applicable to?
What do most installers default to? It seems the field of view varies between 81 degrees and 110 degrees, which is quite significant.
In which locations would the 2.8mm and 3.6mm's be better applicable to?
Ok, for overview shots such as something at the top of your house overlooking your entire back yard, so you can watch and make sure your kids or pets are contained in their outdoor pen while your in the kitchen making dinner, id choose a 2.8mm.
For pure security concerns, such as a camera mounted near your front door to capture the face of and ID someone stealing your packages or trying to break in, you'd want a tighter FOV - likely much more than 3.6mm. Probably at least 6mm in the 5231 turret for example.
It depends entirely on the situation. Buy one motorized varifocal camera and then temporarily mount that in each location that you'd want a camera in the future. Play with the zoom until you get the FOV you want/need. Then find and buy a fixed lens camera that is close to what you figured from playing with the varifocal. You'll get close enough, but not perfect, but who cares your saving some money right?
Also different lenses on different sensors Will not be exactly same FOV.
This is the exact scenario i went thru when i decided to add to cheap cheap cameras watching something outside 99% for entertainment.
Chicken Coop Camera Suggestions
For pure security concerns, such as a camera mounted near your front door to capture the face of and ID someone stealing your packages or trying to break in, you'd want a tighter FOV - likely much more than 3.6mm. Probably at least 6mm in the 5231 turret for example.
It depends entirely on the situation. Buy one motorized varifocal camera and then temporarily mount that in each location that you'd want a camera in the future. Play with the zoom until you get the FOV you want/need. Then find and buy a fixed lens camera that is close to what you figured from playing with the varifocal. You'll get close enough, but not perfect, but who cares your saving some money right?
Also different lenses on different sensors Will not be exactly same FOV.
This is the exact scenario i went thru when i decided to add to cheap cheap cameras watching something outside 99% for entertainment.
Chicken Coop Camera Suggestions
There is no "default", IMO.
Most folks here go for the smallest FOV, but everyone's FOV is 100% unique, depending on where the camera is going, and how wide of a shot is needed. i.e. my front porch is different from your front porch, so what I choose for mine isn't necessarily going to be the best choice for yours
The wider the FOV, the lower the distances for DORI -- detect, observe, recognize and identify.
For example, a fixed 2.7mm Starlight turret will have a wider FOV (i.e. you'll get more in the image <left to right>), but you can only identify things 13 feet out from the camera. With a 3.6mm, you'd be able to identify things 20 feet out from the camera. As the mm's increase, the distance away from the camera that you can identify things also increases. But .. the FOV shrinks...
This is why varifocal cameras are so popular, you don't have to "compromise" by getting a fixed lens camera that gives you a FOV that probably isn't perfect for your shot. With fixed lens, your FOV is almost either too wide (which means you're recording extra stuff on the left/right that you don't care about, at the expense of DORI distances), or too narrow, which means you're missing stuff.
Most folks here go for the smallest FOV, but everyone's FOV is 100% unique, depending on where the camera is going, and how wide of a shot is needed. i.e. my front porch is different from your front porch, so what I choose for mine isn't necessarily going to be the best choice for yours
The wider the FOV, the lower the distances for DORI -- detect, observe, recognize and identify.
For example, a fixed 2.7mm Starlight turret will have a wider FOV (i.e. you'll get more in the image <left to right>), but you can only identify things 13 feet out from the camera. With a 3.6mm, you'd be able to identify things 20 feet out from the camera. As the mm's increase, the distance away from the camera that you can identify things also increases. But .. the FOV shrinks...
This is why varifocal cameras are so popular, you don't have to "compromise" by getting a fixed lens camera that gives you a FOV that probably isn't perfect for your shot. With fixed lens, your FOV is almost either too wide (which means you're recording extra stuff on the left/right that you don't care about, at the expense of DORI distances), or too narrow, which means you're missing stuff.
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For example, here's what a 2.8mm looks like on my front porch. It was the first camera I bought, and totally the wrong lens size for my porch.
Notice how wide the FOV is. So instead of being the porch cam, it's the porch/yard/driveway cam, at the expense of when people walk up to the front door, this camera catches less detail of them than if I had used a bigger mm lens here.
A 6mm lens here would probably narrow the FOV to where only the porch is in the shot... and it would increase the detail on the people who walk up to the front door.
I will replace this camera eventually with a varifocal, so I can zoom it precisely to how I want the FOV to be. Maybe I want a little bit of the sidewalk from the driveway in the FOV. Or maybe not, maybe I want to zoom the FOV in even tighter, focusing more on the front door. That's what's great about varifocals. You're not stuck with just one FOV and can adjust as you figure out what shot works best for you.
Notice how wide the FOV is. So instead of being the porch cam, it's the porch/yard/driveway cam, at the expense of when people walk up to the front door, this camera catches less detail of them than if I had used a bigger mm lens here.
A 6mm lens here would probably narrow the FOV to where only the porch is in the shot... and it would increase the detail on the people who walk up to the front door.
I will replace this camera eventually with a varifocal, so I can zoom it precisely to how I want the FOV to be. Maybe I want a little bit of the sidewalk from the driveway in the FOV. Or maybe not, maybe I want to zoom the FOV in even tighter, focusing more on the front door. That's what's great about varifocals. You're not stuck with just one FOV and can adjust as you figure out what shot works best for you.
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Thanks, I also came across this video as well which attempts to ascertain the differences,
bug99
Pulling my weight
- Dec 27, 2016
- 398
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I agree with the points made above. Every situation is different and there is no one best for most situations.
@aristobrat that is a very good placement of the 2.8mm at the front door.
That all being said, personally, i am fond of the 3.6mm (87 deg FOV) lens, especially indoors. I like the ~90 deg used in corner installs set out a foot or two from the corner and tilted down a bit so that the walls don't enter the frame for a few feet. This gives a large boost to the ppf at 15 ft compared to 2.8. I find that the 2.8 (110 deg) is good (not great) on the center of a wall for overview, but normally would prefer 2 87 deg vs one 110 deg, but that is of coarse not a fair comparison.
As great as @aristocrat's placement / view is, if it were me in hindsight, i would use a 87 deg and rotate it so that i could not see the front door (maybe miss it by 16 inches to just catch packages there), and then have the boost in ppf at the door and still get the cars and sidewalk for at least recognition and maybe ID.
@aristobrat that is a very good placement of the 2.8mm at the front door.
That all being said, personally, i am fond of the 3.6mm (87 deg FOV) lens, especially indoors. I like the ~90 deg used in corner installs set out a foot or two from the corner and tilted down a bit so that the walls don't enter the frame for a few feet. This gives a large boost to the ppf at 15 ft compared to 2.8. I find that the 2.8 (110 deg) is good (not great) on the center of a wall for overview, but normally would prefer 2 87 deg vs one 110 deg, but that is of coarse not a fair comparison.
As great as @aristocrat's placement / view is, if it were me in hindsight, i would use a 87 deg and rotate it so that i could not see the front door (maybe miss it by 16 inches to just catch packages there), and then have the boost in ppf at the door and still get the cars and sidewalk for at least recognition and maybe ID.
I had 2.8 and 3.6mm and last 6 mm fixed Lenses tried for this situation. The best thing that could happen to me was buying this varifocal cam (
Dahua IPC-HDW5231R-Z). I can now adjust as desired. See the Pictures. The trail has about 15 meters
1.Picture approx 2.7 mm
2.Picture approx. 4 mm
3.Picture approx 6 mm
4.Picture about 12mm
i am now happy...;-)
Dahua IPC-HDW5231R-Z). I can now adjust as desired. See the Pictures. The trail has about 15 meters
1.Picture approx 2.7 mm
2.Picture approx. 4 mm
3.Picture approx 6 mm
4.Picture about 12mm
i am now happy...;-)
looney2ns
IPCT Contributor
Except located close to a front door, 2.8mm is almost worthless outdoors.
You want to know who did it, not just what happened. This comes more into play after dark.
The Dahua Starlight Varifocal Turret (IPC-HDW5231R-Z) is really the best of the best and will fit most consumers home setups.
Correct if you are installing a camera for security. I have a few 2.8 mm cams for overview and am happy with them. But i absolutely don't expect to identify someone i don't know with them.
looney2ns
IPCT Contributor
Learn how to use this: Camera Calculator / Design Software keep PPF>100, tutorial upper left. It will give you an idea of the lens you need.
I like the way your 2.8 looks.
I get your point about a tighter shot ( longer lens ) would get just the porch and better assist in identifying someone you don't know. Obviously, most newbies have cam that're far to wide for their application. Like the NestCams of the world—the FOV is too wide. At first glance it seems great until you are trying to ID someone 50 feet away. Robert
Ubaid-Dahua
n3wb
mat200
IPCT Contributor
- Jan 17, 2017
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hmmm.. looks like Dahua is not using 100ppf to calculate the DORI identify distance. Wondering what equation they are using.
Don't have time to look this up more at the moment, but Googling the first part of it came back with a blurb on one of their product pages.
EPC230U | Dahua Technology - Dahua Technology
mat200
IPCT Contributor
- Jan 17, 2017
- 15,986
- 26,891
I'm going to buy one 2.8 and one 3.6. I'm using 12 cameras total so I'll test each focal length and see which works best. If neither works in a certain area then maybe I'll get a varifical lenses in that spot.
aristobrat, I think 2.8mm is good for an "overall" view, but not for identification purposes. Having the sidewalk in the picture may help give a little more detail on the whereabouts of the subject / object, but not on the facial details. It wouldn't look good having two cameras on the same exact spot. However, where you currently have it mounted, with sidewalk in view, is not bad at all because of the distance between the distance of the camera mounting spot and porch. Not every situation will be the same for everyone. I can see why many do not recommend 2.8mm for outdoors.
tibimakai
Known around here
Sorry to revive this old thread, but I did not want to open another thread about the same subject.
If I understand correctly, if I would like to see only the alley in front of my house, I would have to choose a 6mm fov camera(T5442TM-AS)?
If I understand correctly, if I would like to see only the alley in front of my house, I would have to choose a 6mm fov camera(T5442TM-AS)?