Question 1

What is the equivalent focal length of the Mamiya 645 AF APO 300mm f/4.5 in 35mm terms?

Accepted Answer

The 645 medium format sensor is larger than a 35mm full-frame sensor, so the conversion works in the opposite direction to crop-sensor cameras. The 645 format has a crop factor of roughly 0.62x relative to 35mm, which means 300mm on this lens covers an angle of view equivalent to approximately 188mm on a 35mm camera — a wider field of view than a 300mm full-frame telephoto, not a narrower one. It's still a strong telephoto focal length, very usable for sports and wildlife, but photographers switching from 35mm gear should expect a noticeably broader frame than they're used to at 300mm.

Question 2

Is this lens compatible with Phase One camera backs?

Accepted Answer

Yes. The Mamiya 645 AF APO 300mm f/4.5 uses the Phase One / Mamiya 645 mount, which is the same mount used by Phase One medium format digital backs and bodies. Autofocus functions correctly on compatible AF-capable 645 bodies. If you're using an older M645 (manual focus) body, be aware that pin and flange differences between the 645AF and M645 systems can prevent correct mounting — always verify body compatibility before buying.

Question 3

Is the Mamiya 645 AF APO 300mm f/4.5 difficult to get sharp results from?

Accepted Answer

Medium format telephoto lenses at 300mm demand solid technique. Shutter speed, support, and mirror lock-up (where available) all make a meaningful difference. Shooting handheld or from an unstable position at slower shutter speeds is where most Use a sturdy tripod or monopod, dial in a fast enough shutter speed for the focal length, and the APO design will reward you with well-corrected, detailed images.

Question 4

How does the Mamiya 645 AF APO 300mm f/4.5 compare to the Mamiya Sekor C 300mm?

Accepted Answer

The Sekor C 300mm is a manual focus M645-mount lens from an earlier era, while this APO 300mm f/4.5 is built specifically for the autofocus 645AF system. Autofocus is a practical advantage for sports and wildlife. The APO optical correction also makes a difference for controlling colour fringing — chromatic aberration is better managed in the later APO design. If you need manual-only shooting on an older Mamiya body, the Sekor C remains a usable option, but for modern digital backs the AF APO version is the more capable choice.

Question 5

Is buying a used Mamiya 645 AF APO 300mm f/4.5 worth it?

Accepted Answer

A pre-owned Mamiya 645 AF APO 300mm f/4.5 makes sense if you're already invested in the Phase One / Mamiya 645 system and need serious telephoto reach. New medium format telephoto glass in this focal range is expensive and rarely produced today, so the second-hand market is effectively the only route. Every used lens on Camera-tweedehands.nl is professionally inspected, individually photographed, and comes with a minimum 12 months warranty — so you're not buying blind.

Question 6

Are there alternative lenses to consider in the Mamiya 645 telephoto range?

Accepted Answer

Within the 645AF system itself, options at the long end are limited. There are zoom options in the system that cover the mid-telephoto range but top out well below 300mm. For photographers who need to push further out, the 300mm APO prime is one of the few dedicated options available. Outside the Mamiya system, Pentax 645 and Bronica lenses are sometimes mentioned as alternatives for medium format telephoto work, but they require different bodies and backs — cross-system compatibility is not straightforward.

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Mamiya 645 AF APO 300mm f/4.5

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About the Mamiya 645 AF APO 300mm f/4.5

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