2.8mm vs 3.6mm test

[namtrab]

Good morning (or evening, depending on where you are!). I currently have a couple Starlight -HDW5231R-Z cams up and running. I am looking at picking up a mini-wedge HDBW4231F-AS for use as a front door cam (shaded, covered porch area). As others have tried to determine, should I go 2.8 or 3.6 since the mini wedge is a fixed lens.

So, I was going to do a little testing to at least "get close" to an idea on what each lens size would look like. I am going to take one of my current Starlights and temporarily mount it and test how it would look with each lens size by adjusting the zoom.

Now, getting an idea what a 2.8 would look like is easy, since the HDW5231R-Z is varifocal from 2.7 to 12mm. Just simply zoom all the way out, and that will give a pretty good idea what a 2.8 fixed would look like.

Now, trying to determine what a 3.6 would look like would be a little "tougher". By logging into the camera itself, how far should the slider be adjusted to simulate what 3.6mm would look like? At what point on the zoom would give a fairly accurate representation of what a 3.6mm lens would look like? When hovering the mouse cursor over the slider marker, a number appears (not sure what that number even means, but the further up the slider you go, the larger the number gets).

Just getting "close" is good enough for me. I know doing a test like this is "not perfect", but at least having an idea what a 3.6 would look like as far as coverage is better than no idea at all!

Thank you much!

 

[aristobrat]

I had a similar project, except for the back porch. I was happy with the 2.7mm view from my 5231R-Z, so I bought a 2.8mm 4231F-AS... and was kind of surprised when I mounted it and saw how wide the view actually was...

Looking at the spec sheets:

2.7mm = 97° angle of view on the 5231R-Z, whereas
2.8mm = 110° angle of view on the 4321F-AS.

IMO, that's a pretty big difference in angles from the focal lengths just being one MM off. Don't know if this is because the 5231 has a 4x optic zoom or what...

Kinda hard to see below, but the 4231 is in green (and has the wider view). The 5231R-Z is in blue, narrower view.



I'm kind of confused about this, as I've long seen folks told to do what you're trying to do. I always thought they meant "zoom the 5231 out to the MM of the camera you want to buy, and see if the view works", but it seems like you need to forget comparing about matching the MM and zoom the 5231 out to match the angle of the camera you're looking to buy instead.

I may be totally off-base here, so def. wait until someone with some more experience chimes in. @fenderman @looney2ns

 

[namtrab]

Thanks, Aristobrat. Good point about the specs. I didn't even think about that part (spec reading).

Specs aside, since you have gone through this, you would say that the 2.8 on the wedge is actually wider than the 2.7 on the turret (not just by specs, but by actually seeing the cams in action)? If this really is the case, and I'm pretty much happy with how the turret 2.7mm looks, but maybe just a bit wider than necessary, I guess I could slightly envision the view being "slightly smaller" if a 3.6 was used. 97* with the turret at 2.7mm vs 87* with the wedge at 3.6mm. So my thinking would be that if 97* is still more than necessary, 87* would be better (if not perfect), and therefor the wedge with 3.6mm would be the way to go.

I guess I should toss in that I will be testing (and using) the cam in corridor mode. So, width in "standard mode" will become height in real world use. Not that it really matters, but just in case there is some other variable I'm not thinking about.

 

[looney2ns]

It partially depends on what you want to see.
Do you just want to see faces or do you want to see faces and packages laying right up against the front door.
If you only care about faces, then the 3.6mm will do, if mounted at approx 5ft.

The FOV also depends on the size of the sensor.
See if this helps:
dahua focal length vs fov - what is the truth

 

[mat200]

Good morning (or evening, depending on where you are!). I currently have a couple Starlight -HDW5231R-Z cams up and running. I am looking at picking up a mini-wedge HDBW4231F-AS for use as a front door cam (shaded, covered porch area). As others have tried to determine, should I go 2.8 or 3.6 since the mini wedge is a fixed lens.
..
Thank you much!

Hi Nam, I went with a 2.8mm on the mini-wedge HDBW4231F-AS as it is right next to my front door, and thus subjects could be as close as 2-3 feet from the lens. ( I have another camera covering the approach )

 

[Mr_D]

It partially depends on what you want to see.
Do you just want to see faces or do you want to see faces and packages laying right up against the front door.
If you only care about faces, then the 3.6mm will do, if mounted at approx 5ft.

The FOV also depends on the size of the sensor.
See if this helps:
dahua focal length vs fov - what is the truth

I'm actually planning on a 6mm wedge for my front door. People approaching the door must first go through an arch about 10' away so there's a natural choke point. I figure 6mm will give me lots of detail before they even get that far. I currently have a Ring doorbell which gives an ultra wide angle view but still doesn't quite catch the doormat. I'm considering a second 2.8mm wedge, possibly mounted above the door, to give an overview of the entry area.