Mathematical Problem

[Churchill]

Wouldn't a nice ferris wheel look better than a chimney ?

Or a big fck off shrubbery?

As in the Knights Who Say "Ni!"...

[Zippy]

That will be hard when the other things in the pic are at different distances though

No, it wil be impossible unless you get some more information. If other buildings are close you might get something that's good enough.

Do you know how far the chimney is from other buildings? Do you know the height of those buildings? Are there any artifacts in that image that you can Google to get more information?

[Ticktock]

So this is wanted presumably for either promotional purposes, or planning permission, or similar?

I don't see why you need to get it millimetre perfect. Take a picture of the chimney. Take a picture of the proposed new area. Merge it in and size it by eye.

Surely you can get a reasonable approximation this way.

[Freaki Li Cuatre]

No, it wil be impossible unless you get some more information. If other buildings are close you might get something that's good enough.

Do you know how far the chimney is from other buildings? Do you know the height of those buildings? Are there any artifacts in that image that you can Google to get more information?

But surely if I know the focal length of the lens used to take the pic there must be some calculation that can be used in conjunction with the earlier mentioned linear perspective formula?

[EternalOptimist]

Go to see the guy who maintains the brickwork of the chimney, then say to him
'I will let you have this marvelous camera, if you will tell me how big this chimney is'

[Zippy]

But surely if I know the focal length of the lens used to take the pic there must be some calculation that can be used in conjunction with the earlier mentioned linear perspective formula?

Ohhhh I see - slow day is it?

[Freaki Li Cuatre]

Ohhhh I see - slow day is it?

[vetran]

you trying to fix the problem or is it an intellectual exercise?

If the former then Sketchup.

If the latter, have fun.

[alluvial]

Okay.
I=fh/d
Where I is image size
F is focal length
H is object size
D is distance to object

This should give you the size of the chimney at the camera's sensor surface.
You can then create your chimney image to size and stick it in the image on something that is at the correct distance.

Of course this may all be screwed up if the image had been processed as if converted to jpg then this won't hold. If you have access to the RAW file you may be able to do this.

[Freaki Li Cuatre]

Okay.
I=fh/d
Where I is image size
F is focal length
H is object size
D is distance to object

This should give you the size of the chimney at the camera's sensor surface.
You can then create your chimney image to size and stick it in the image on something that is at the correct distance.

Of course this may all be screwed up if the image had been processed as if converted to jpg then this won't hold. If you have access to the RAW file you may be able to do this.

Yes, the pic is Jpeg. Does that alter the scale then?