How to Calculate Extreme Close Up Magnification With a Bellows

Hi, I would like to ask you if the following formula I found online is reliable for calculating extreme close up magnification With a bellows:

New Magnification = nM
Original Magnification of Lens = M
Total Extension = T (in mm)
Focal Length of Lens = F (in mm)

nM = M + T/F

Thank you very much.

There are usually too many variables to accurately calculate magnification. You'll get somewhere in the ballpark though, which is often good enough and may suit your needs just fine. It's your only option if you don't have the optics in hand anyway (i.e. if you're figuring out what you need to get). But direct measurement is always best - when you can.

I photograph a stage micrometer (aka microscopic ruler) and use the dimensions of the sensor/pixels to precisely calculate actual magnification from the image.

Beatsy wrote:

There are usually too many variables to accurately calculate magnification. You'll get somewhere in the ballpark though, which is often good enough and may suit your needs just fine. It's your only option if you don't have the optics in hand anyway (i.e. if you're figuring out what you need to get). But direct measurement is always best - when you can.

I photograph a stage micrometer (aka microscopic ruler) and use the dimensions of the sensor/pixels to precisely calculate actual magnification from the image.

Thanks for your words. You are absolutely correct. I am in the process of changing some lenses and the probable acquisition of the bellows, so this exercise, even if it is not completely accurate, serves to obtain a sufficiently approximate idea to be able to make decisions regarding the change of lenses.

BBbuilder467 wrote:

Pansottin wrote:

Beatsy wrote:

There are usually too many variables to accurately calculate magnification. You'll get somewhere in the ballpark though, which is often good enough and may suit your needs just fine. It's your only option if you don't have the optics in hand anyway (i.e. if you're figuring out what you need to get). But direct measurement is always best - when you can.

I photograph a stage micrometer (aka microscopic ruler) and use the dimensions of the sensor/pixels to precisely calculate actual magnification from the image.

Thanks for your words. You are absolutely correct. I am in the process of changing some lenses and the probable acquisition of the bellows, so this exercise, even if it is not completely accurate, serves to obtain a sufficiently approximate idea to be able to make decisions regarding the change of lenses.

I think the main issue is the adaptation when you don't know the original register distance.

I need a 25mm spacer with my system before I calculate the extension, then it's accurate. I can't include that 25mm in the equation or I'd be off by 0.5x with a 50mm lens.

Good point .-)