Varifocal Understanding

8urt0

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I understand the lens size affects how "zoomed in" the picture looks for example 22mm is very zoomed in compared to 2mm a wide angle.

Where I am having trouble is truly understanding varifocal. Does varifocal only mean the lens can be moved from one to the other effectively zooming (either manual or through software). I feel like i have been trying to read up on this for a week now but for some reason I am just not getting it.

From what I can gather varifocal would be only good if you are unsure of the horizontal angle you want to cover?

(I think I have been trying to absorb too much)
 

DavidR1

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I understand the lens size affects how "zoomed in" the picture looks for example 22mm is very zoomed in compared to 2mm a wide angle.

Where I am having trouble is truly understanding varifocal. Does varifocal only mean the lens can be moved from one to the other effectively zooming (either manual or through software). I feel like i have been trying to read up on this for a week now but for some reason I am just not getting it.

From what I can gather varifocal would be only good if you are unsure of the horizontal angle you want to cover?

(I think I have been trying to absorb too much)
It sounds like you've more or less got it, though I'd argue that more than just covering a situation where you're "unsure of the horizontal angle you want to cover", a camera with a varifocal lens lets you dial in exactly the viewing angle required for a given location and scene -- rather than just "getting pretty close" with whatever the nearest fixed lens offering happens to be. @aristobrat recently shared a real world example from his personal experience showing why he argues for varifocal cameras.

It's a huge advantage being able precisely set the field of view to maximize the effectiveness of a given sensor's available pixels - anywhere between the two limits shown in the camera's specifications. For example, the IPC-HFW5231E-Z12 is advertised as being adjustable to anywhere in between 5.3mm to around 64mm though software. This flexibility allows the camera to be used for different tasks in different installations - some use it with a very narrow field of view for license plate capture while others use the same camera to take advantage of its ability to "reach out" to properly cover a point of interest further away from the camera's mounting location than they might otherwise be able to with commonly available fixed lenses.

It's typically recommended here that everyone start out with at least one varifocal camera, as it's a great tool along with a test rig for real-world, on-site testing to determine optimal camera placement and lens selection for subsequent camera purchases. Using varifocal lenses all over can also make it easy to re-purpose cameras down the road if/when your needs change.

I realize now that my long-winded response has only added to your week of reading but I hope that helps! ;)
 

8urt0

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It sounds like you've more or less got it, though I'd argue that more than just covering a situation where you're "unsure of the horizontal angle you want to cover", a camera with a varifocal lens lets you dial in exactly the viewing angle required for a given location and scene -- rather than just "getting pretty close" with whatever the nearest fixed lens offering happens to be. @aristobrat recently shared a real world example from his personal experience showing why he argues for varifocal cameras.

It's a huge advantage being able precisely set the field of view to maximize the effectiveness of a given sensor's available pixels - anywhere between the two limits shown in the camera's specifications. For example, the IPC-HFW5231E-Z12 is advertised as being adjustable to anywhere in between 5.3mm to around 64mm though software. This flexibility allows the camera to be used for different tasks in different installations - some use it with a very narrow field of view for license plate capture while others use the same camera to take advantage of its ability to "reach out" to properly cover a point of interest further away from the camera's mounting location than they might otherwise be able to with commonly available fixed lenses.

It's typically recommended here that everyone start out with at least one varifocal camera, as it's a great tool along with a test rig for real-world, on-site testing to determine optimal camera placement and lens selection for subsequent camera purchases. Using varifocal lenses all over can also make it easy to re-purpose cameras down the road if/when your needs change.

I realize now that my long-winded response has only added to your week of reading but I hope that helps! ;)
Mate that's the best reading I have had all night. I have got it. Appreciated the link to @aristobrat share as well. I saw some great examples of test rigs on here. I was thinking just estimating the horizontal field of view was enough to determine but you have made me realise repurposing cameras changes everything. And as I move to this new NVR system this is going to be a big thing as I was already thinking the camera I have purchased for my front door was a starting point and I planned to move it another place around the house in the future once I decide exactly what I want there.

I am now officially converted to a varifocal state of mind Thank you.
 

mikeynags

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I also agree with going varifocal wherever you can. I have one camera that is "tucked in" to a corner next to a chimney and to get the camera view set perfectly, the varifocal helps me dial it in so that the chimney is not in the view at all. Much better than a digital zoom also, it maintains focus all the way in and out.
 
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