Field of View from Picture?

[John Esher]

We just moved and I'm trying to set up my old cameras in their new locations. I have two placed, at least temporarily, and want to get two more. But I'm unsure of the focal length I need – 2.8 or 4mm.

If I climb up the ladder and position my iPhone where I'd like to place the camera, is there any software (or manual masking method) to obtain an approximate view of what I'd see with the different focal length cameras? Or will it not work because I can't change the focal length of the iPhone? Maybe I should use a DSLR...

Granted, I guess I could make an extra long cable and string it through the window and take down one of my old ones, but I don't currently have a 2.8mm

 

[Zxel]

Check out searching on google for "camera fov calculator" - here is one I found (but there are several) http://www.supercircuits.com/resources/tools/fov-calculator.

 

[fenderman]

What cameras are you looking at? for focal length is not the only measure to determine field of view...yes for the same camera 2.8 will be wider than 4..but you cannot compare two cameras that dont use the same sensors...

 

[Zxel]

You can also check out the tool @fenderman posted in this thread.

 

[John Esher]

Zxel, thanks for that link, I had been there.

Fenderman, I don't have any specific one just yet.

I'm just trying to figure out what the FOV would look like from under the eave on the side of the house. With my specific view in the frame. Numbers on a tape don't cut it for me. Just trying to minimize the trips up and down the ladder (not a fan of heights) and having to return a camera because the view is too restricted or too wide.

I guess i was was thinking of something like a filter or crop in image editing software.

 

[Zxel]

What iPhone and camera model are you using? I'm willing to do the math for you to translate the phone pic into the camera pic, but no guarantees on accuracy (have to cover my butt).

 

[John Esher]

What iPhone and camera model are you using? I'm willing to do the math for you to translate the phone pic into the camera pic, but no guarantees on accuracy (have to cover my butt).

An iPhone 5 and I'm looking at something in the 4mm and 2.8mm range. I have Hik's now, but I'm not adverse to trying a Dahua...

 

[LittleBrother]

You can do this more or less. 2.8 is about 90 degrees horizontally and 4 mm is 70. Your iphone is tighter than either one. Stand on a ladder and eyeball something to your left and your right. If it's a driveway, for example, the driveway is likely to come off the house at a perpendicual 90 degree angle, so you can figure out what you'll have, or hold your hands at an angle. Or stich two images from your iphone together and cut 90 and 70 degree snippets from the combined pic.

You could also read this, though it's heavy in geek factor http://www.wired.com/2013/05/calculating-the-angular-view-of-an-iphone/

This is awesome: http://www.boinx.com/chronicles/2013/3/22/field-of-view-fov-of-cameras-in-ios-devices/

 

[John Esher]

You can do this more or less. 2.8 is about 90 degrees horizontally and 4 mm is 70. Your iphone is tighter than either one. Or stich two images from your iphone together and cut 90 and 70 degree snippets from the combined pic.

Hmm, I think I'll go up and take a panorama shot approximating 90 and 70 degrees.

Thanks!

 

[Zxel]

You can do this more or less. 2.8 is about 90 degrees horizontally and 4 mm is 70. Your iphone is tighter than either one. Stand on a ladder and eyeball something to your left and your right. If it's a driveway, for example, the driveway is likely to come off the house at a perpendicual 90 degree angle, so you can figure out what you'll have, or hold your hands at an angle. Or stich two images from your iphone together and cut 90 and 70 degree snippets from the combined pic.

You could also read this, though it's heavy in geek factor http://www.wired.com/2013/05/calculating-the-angular-view-of-an-iphone/

This is awesome: http://www.boinx.com/chronicles/2013/3/22/field-of-view-fov-of-cameras-in-ios-devices/

That last link IS awesome, you did it better than I could. Thank You.