Mamiya Apo-Sekor-Z 350mm f/5.6 on Fuji GFX

The Mamiya Apo-Sekor Z 350mm f/5.6 is a medium format lens for Mamiya RB/RZ 67. It covers a much bigger image circle than the Fujifilm GFX 100S.

It can be acquired quite cheaply these days — only $300 on eBay! However, you’ll need an expensive adapter, such as the Fotodiox Pro RB/RZ to GFX adapter, which costs more than the lens, bringing the total to about $700.

From the manual, you can find the lens construction diagram, MTF, and chromatic aberration plots. The MTF honestly looks great even by modern standards, so let’s see if it lives up to the hype!

In fact, the 350mm is the sharpest out of the Mamiya RB/RZ Apo lenses, having more than an MTF of 0.8 at 40 lp/mm according to the MTF plot. On the Fuji GFX, we’re only using the middle part of the MTF, up to 27 mm.

Generally, I found that it is indeed very sharp and apochromatic!

However, the main drawback of this lens is the poor ergonomics. The lens doesn’t have a focusing helicoid, and the helicoid is on the adapter. But the lens is super heavy, so if your hand is supporting the lens at its center of mass, it would be far from the helicoid, and if your hand were on the helicoid, it would feel very out of balance. This makes the manual focus experience unpleasant to use on the GFX.

Furthermore, to keep the aperture open at the desired aperture, you need to press down on an aperture lever. On the RB/RZ bodies, it would electronically set the aperture at the moment of taking the photo (as it engages the leaf shutter), but when adapted on mirrorless cameras, you’ll have to keep pressing that lever to keep the aperture open at the desired setting setting. In practice, the lens is sharp enough (and quite slow) that I never need to stop down.

Another quirk is that the adapter with helicoid is prone to sagging with the heavy lens, causing shots at infinity to not have even sharpness. This can typically be fixed with a long lens support, adding to the weight and complexity of the kit.

Finally, it is a slow, long, manual lens, obviously without image stabilization, so it is easy to have blurry photos due to camera shake.

So without further ado, here are some full resolution, unprocessed, uncropped 100 megapixel photos!