NiSi Cine Lens Athena Prime 40mm T1.9 RF-Mount

NiSi Cine Lens Athena Prime 40mm T1.9 RF-Mount – Fast T1.9 aperture with Drop-In filter option

The NiSi Athena Prime 40mm T1.9 in RF-mount brings the Athena series’ cinematic characteristics to Canon RF cameras. It shares the same optical design goals as the rest of the Athena Prime family: consistent exposure, minimal focus breathing, and versatile filtration options. This 40mm lens has a maximum aperture of T1.9, which makes it possible to achieve soft bokeh and attractive background separation.

Key optical features

The Athena series delivers uniform T-stop performance across multiple focal lengths. Specifically, the 40mm model offers T1.9 light transmission, matching several other primes in the set to ensure consistent exposure when you switch lenses. In addition, the lenses provide an image circle of 46mm, making them suitable for full-frame and even large-format sensors.

Filtration system and mount-specific options

NiSi equips the Athena Prime series with a proprietary rear filtration system. For RF, L and G mounts the lenses include a Drop-In filter option. The E-mount is offered in two versions: one with the Drop-In filter and one without. The PL-mount uses a rear filter instead of a Drop-In module.

• Sony FX9 cameras cannot use the E-mount version with Drop-In filters.
• To achieve infinity focus and clear images, it is important to use the Drop-In clear filter on RF-, L- and G-mounts (and on the E-mount version that includes the Drop-In option), and to use the rear filter on PL-mount lenses.

NiSi also provides weather sealing for the Drop-In filter, which helps protect the filtration system during outdoor shoots and in challenging conditions.

Handling, controls and uniformity across the series

The Athena Primes are designed to behave like a matched set. All lenses in the range are similar in weight, so you do not need to re-balance a gimbal when switching between Athena lenses. Except for the 14mm, all lenses use the same 77mm front filter thread, simplifying filter and accessory choices across the set.

Both aperture and focus rings are matched across the range for consistent hand feel. Each lens offers a 300° focus rotation together with fluorescent focus scales displayed in both imperial and metric units to support precise focus pulls. Furthermore, the lenses use standard 0.8 mod focus and iris gears, making them compatible with a wide range of follow focus and matte box systems.

Accessories and close-up options

For close-up and macro effects, NiSi offers a 77mm close-up lens (sold separately). This accessory reduces the minimum focus distance and enables more pronounced macro imagery with Athena primes that accept 77mm filters.

Why choose the 40mm RF version

Choose the 40mm RF-mount Athena Prime when you need a mid-tele focal length that matches exposure and handling characteristics across a cinematic prime set. Its T1.9 aperture offers shallow depth-of-field control for subject separation, while the rear filtration options and consistent gear placements make it practical on professional camera rigs.

FAQ

Question: Is the NiSi Athena Prime 40mm available for mounts other than RF?
Answer: The Athena Prime series is available in ARRI PL, Canon RF, Sony E, Panasonic/Leica L and Fuji G mounts. The 40mm model in this listing is the Canon RF version.

Question: Do I need a special filter to reach infinity focus?
Answer: Yes. For RF-, L- and G-mounts (and the E-mount version that includes the Drop-In option) you must use the Drop-In clear filter, and for PL-mount you must use the rear filter to achieve infinity focus and clear images.

Question: Can I swap Athena lenses on a gimbal without rebalancing?
Answer: Yes. All Athena Prime lenses are similar in weight, so switching between lenses in the series does not require rebalancing your gimbal.

Question: Will the 40mm work with follow focus and matte box systems?
Answer: Yes. The lens uses standard 0.8 mod focus and iris gears and has matched aperture and focus rings across the series, ensuring compatibility with most follow focus and matte box setups.

Question: How can I get closer focus or macro effects with this lens?
Answer: You can use the NiSi 77mm close-up lens (sold separately) to reduce minimum focus distance and create macro effects with Athena primes that accept 77mm filters.