How to calculate the Focal Length

[Lincos]

Hi all,

I'm wondering how i have to calculate the Focal Length. I hope someone can help me out.
The picture below is the frontside/entree of my home. I like to install a Turret at the place of the arrow so i have both entrees in my field of view.

My first cheap camera i bought about 15 years ago is mounted above the right door. Just under the roof. It worked about 1 year before it broke. In that time i had a lot of problems with heavy sunshine. That's why i want my Turret on the other wall.

I hope someone can help me out.

Cheers!

 

[Rob2020]

Under tools at the top of the page, there is a focal length calculator;

Here

 

[Lincos]

Ah, thank you. Will try that.

 

[Lincos]

O wow, i think that needs some time

 

[Rob2020]

Take a look at this, it might be useful;

Lens Calculator

 

[Lincos]

I was confused about the 'focal length calculator' because my question was wrong.
I meant to ask how you guys choose the size of the lens.

Both answers are related so i have to do some homework.

Thanks Rob!

 

[wittaj]

See this thread where I mention the most commonly suggested cameras here based on distance to IDENTIFY:

The Importance of Focal Length over MP in camera selection

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...

ipcamtalk.com

 

[Lincos]

That's a very interesting read. Thank you wittaj!

 

[samplenhold]

I meant to ask how you guys choose the size of the lens.

That is a fairly tricky issue.

Personally, I did not buy all of my cams at once. I bought a varifocal version of the latest good prosumer cam at that time. I knew that for several positions I would be using that model, just did not know which lens. Once I had that varifocal cam, I placed it on a test rig and recorded different positions and at different focal lengths, looking at the 2.8, 3.6, and 6mm FOVs to decide which lens cam to get. I knew that I would use the varifocal cam somewhere, which ended up being a position that needed more than the 6mm lens.

Test Rig:

 

[Lincos]

That's also a good idea. In the end there is always a place for the varifocal. Thanks!

Cheers!