RF 100-400mm magnification and focus breathing with distance

[AlanF]

A bit of geek from me about the RF 100-400mm. I do a lot of semi-macro photographing of dragonflies and butterflies with it at 1 to 3m (3-10') and wanted to know what the magnification is at those distances and for amusement how the focal length drops as you get closer to the target. Here is a plot of my measurements of the magnification at close distances and the calculated focal length at each distance. I used the read out of the distance from target to sensor from the exif data - because that is what I know from all the images I take. You can calculate the size of your object from the second graph of magnification vs 1/distance using the equation in the plot (for the R7 I used).

At the minimum focus distance of 950mm at the focal length setting of 400mm, the magnification is 0.43, close to the 0.41 claimed by Canon. The calculated focal length at this distance is 200mm. By 3.5m distance, the focal breathing has improved and the f is 340mm.

The EF 100-400mm II, in comparison, has at 970mm a magnification of 0.31x and f calculated to be 178mm. The RF 100-500mm at 970mm has 0.33x wuth a calculated f of 224mm.

 

[EricN]

That's quite an advantage over Canon's larger, heavier and more expensive options! Hopefully, this can satisfy the people wanting a 180mm macro until one becomes available.

 

[AlanF]

That's quite an advantage over Canon's larger, heavier and more expensive options! Hopefully, this can satisfy the people wanting a 180mm macro until one becomes available.

The closest I do to macro is photographing insects close up and trying to get as much as possible in focus, so having f/8 is no disadvantage as I need to stop down anyway. Also, being a meter away disturbs flighty insects less than getting close. But, I can't get the spectacular close-ups that @koenkooi does.