SO confused with macro bellows formula! PLEASE hellllp ):

[still_learning]

Hello.

Been trying to search for help online with the explanation on how to work out the bellows extension formula!
If anyone can shed some light on anything to do with this, then please do because I don't know where to start.



): waahhhhh

 

[Overread15 3]

The rough maths as I know it is:

( length of the bellows - divided by - focal length of the lens in mm (or extension tube) in mm ) + native magnification of the lens itself at the selected focus point = magnification factor : 1

where:
magnification factor = size of the subject as reflected on the sensor by the lens
1 = size of the subject in real life.

 

[still_learning]

Thank you so much! HUGE help

 

[TheFantasticG]

Why worry about it? When I'm using tubes, teleconverters, and whatnot I don't much care what ratio I'm at. I know when I am as close as I want to be.

 

[Overread15 3]

It can matter if you want a rough idea of the magnification factor; I also tend to find it helps those who want to be able to measure things.

Though for measuring things the best thing is to take a photo, at the same magnification, of a ruler. You can then read how many mm the length of the ruler is in the frame and then and convert that to a magnification factor by comparing it to the actual dimensions of the sensor in the camera.