I am regularly asked a few questions about the variable aperture on the Fujinon (Fujifilm) 100-400mm f/4.5-5.6 and  so as I often do, I decided to write a blog post covering them…

Is there an aperture ring?

Yes! Because the aperture markings are not marked on the lens barrel, it isn’t quite as obvious as other lenses. But it is there, located between the focal length markings and the tripod collar lock screw. As we would expect, it adjusts the aperture with a reassuring tactile increment for each 1/3 of a stop.

Why are there no aperture markings?

Firstly, let’s ask ‘What is a variable aperture lens?’ then we’ll come back to this!

What is a variable aperture lens?

The 100-400mm is a zoom lens with a variable aperture. This means the widest available aperture changes as we increase the focal length of the lens. If the aperture was to stay at a constant f/4.5 throughout the 100-400mm range it would add considerable size and weight to the lens, and costs too.

It doesn’t affect ‘stopping down’ the aperture for exposure. Should you wish to, we can ‘stop down’ towards f/22 at any point in the focal length.

Fujifilm 100-400mm Alan Hewitt Photography

So, why are there no aperture markings?

If you are using the widest f/4.5 aperture at 100mm and you zoom through the focal length to 400mm, the lens automatically narrows the aperture to f/5.6. If the aperture was ‘physically’ marked on the barrel as f/4.5 would be incorrect and confusing.

Zoom lenses such as the Fujinon 50-140mm f/2.8 have a constant aperture throughout their focal length range, it therefore makes sense to have aperture markings on the barrel.

How does the aperture vary throughout the focal length range?

The total difference is between f/4.5 at 100mm and f/5.6 at 400mm. Here we can see exactly where the aperture closes down as we move from 100mm to 400mm…

Focal Length 100mm 107mm 128mm 153mm 183mm 280mm 323mm 347mm
Widest Aperture f/4.5 f/4.6 f/4.7 f/4.8 f/5 f/5.2 f/5.4 f/5.6

Finally, no blog post about a lens can be complete without a photograph taken with that lens, so here are some European Bee-eaters photographed in rural Spain earlier this year!

European Bee-eaters Alan Hewitt Photography

European Bee-eaters – Fujifilm X-H1 & Fujinon 100-400mm f/4.5-5.6 & 1.4x t/c