NiSi Cine Lens Athena Prime 25mm T1.9 RF-Mount

NiSi Cine Lens Athena Prime 25mm T1.9 RF-Mount – Fast T1.9 Aperture for Cinematic Bokeh and Drop-In Filter Support

This NiSi Athena Prime 25mm in Canon RF mount delivers a fast T1.9 aperture for shallow depth of field and smooth background separation. It is part of the Athena Cine Lenses series, designed for cinematographers and videographers who need consistent exposure, matched handling and professional cinema features across a wide focal length range.

Key features for the 25mm RF-Mount

• Max aperture T1.9 for the 25mm focal length, allowing soft bokeh and reliable low-light performance.
• Canon RF mount version with a Drop-In filter option for flexible filtration and creative control.
• Large 46mm image circle that covers full-frame and large-format sensors.
• Matched mechanical characteristics across the Athena series: similar weight, matched aperture and focus rings, and 77mm filter thread on lenses except the 14mm.
• Proprietary rear Drop-In filter system on RF-mount, including weather sealing for the Drop-In filter.

Optical performance and aperture series details

The Athena series delivers consistent exposure through true T-stop ratings. For clarity across the set, NiSi specifies T-stops for multiple focal lengths: 25/35/40/50 & 85mm have a maximum aperture of T1.9; 18mm and 135mm are T2.2; and the 14mm is T2.4. These values reflect the actual light transmission for predictable exposure when swapping lenses or cutting between focal lengths.

The lenses emphasize ultra-low chromatic aberration and controlled micro-contrast to retain finer image details. In addition, the design minimizes focus breathing so that changes in field of view while pulling focus remain extremely small.

Mounts, filters and important notes

The Athena Prime series is available in many mounts, including ARRI PL, Canon RF, Sony E, Panasonic/Leica L and Fuji G. The RF-, L- and G-Mount lenses feature a Drop-In filter option. The E-Mount is available in two versions (with and without Drop-In filters), while PL-mount uses a rear filter.

Important: It is necessary to use the Drop-In clear filter on RF-, L- and G-mount (and the correct Drop-In version for E-mount) and to use the rear filter on PL-mount to achieve infinity focus and clear images. Also note that the Sony FX9 camera cannot use the E-Mount version with Drop-In filters.

NiSi supplies a weather-sealed option for the Drop-In filter to help protect the filter assembly in demanding shooting conditions.

Mechanical design and handling

NiSi matched the mechanical feel across the Athena line. All lenses share similar weight so you typically do not need to rebalance your gimbal when switching between Athena lenses. With the exception of the 14mm, lenses use a 77mm front filter thread for standard screw-on filters.

Both aperture and focus rings are matched across the range. The focus rotation is 300°, and the fluorescent focus scales display both imperial and metric units for accurate focus pulls in dim light. Standard 0.8 mod focus and iris gears ensure compatibility with common follow focus and matte box systems.

Accessories and close-up options

To reduce minimum focus distance and create macro effects, NiSi offers a 77mm close-up lens that can be used with Athena lenses. This accessory is sold separately and provides a practical way to capture tighter close-ups without changing optics.

FAQ

Question: Is the RF-mount 25mm Athena lens compatible with Drop-In filters?
Answer: Yes. The Canon RF version supports a Drop-In filter option. For correct infinity focus and clear images, you must use the Drop-In clear filter with RF-mount Athena lenses. NiSi also offers a weather-sealed Drop-In filter.

Question: Will the Athena 25mm cover full-frame or larger sensors?
Answer: Yes. The Athena series provides a 46mm image circle, making it suitable for full-frame and many large-format sensors.

Question: Do I need to rebalance my gimbal when switching between Athena lenses?
Answer: Generally no. All Athena Prime lenses are similar in weight, so you typically do not need to rebalance when swapping lenses within the series.

Question: Can I use the E-mount Drop-In version on a Sony FX9?
Answer: No. The Sony FX9 camera cannot use the E-Mount version that includes Drop-In filters, so plan mount and filter options accordingly.

Question: How can I achieve close-up or macro effects with the Athena 25mm?
Answer: Use the NiSi 77mm close-up lens (sold separately) to reduce the minimum focus distance and create stronger macro effects without changing your primary lens.