NiSi Cine Lens Athena Prime 40mm T1.9 G-Mount (Without Drop-in Filter)

NiSi Athena Prime 40mm T1.9 — G-Mount (Without Drop-In Filter) — Fast T1.9 for soft bokeh

This NiSi Athena Prime 40mm lens in G-Mount is part of the Athena Cine Lens series designed for cinematographers and videographers who demand consistent exposure and cinematic rendering. The 40mm delivers a maximum aperture of T1.9, enabling soft bokeh and clear background separation when you need it.

Designed for filmmaking and video work

The Athena Prime series targets filmmakers and videographers. NiSi engineered the lenses with filmmaking workflows in mind, matching aperture and focus ring placement across the series. As a result, you can switch lenses without changing handling or pull techniques.

Moreover, all lenses (except the 14mm) share the same 77mm front filter thread, which simplifies filter management during production. The 40mm G-Mount version listed here ships without the Drop-In filter installed, so be aware of the mount-specific filter requirements explained below.

Optical performance and aperture characteristics

The Athena Prime line covers a wide range of focal lengths from 14mm ultra-wide to 135mm portrait and telephoto. Within that line, the 40mm sits among lenses that offer a fast T1.9 maximum aperture (25, 35, 40, 50, and 85mm). The faster aperture family members allow for shallow depth of field and attractive bokeh for subject separation.

Other T-stop values in the series include T2.2 for the 18mm and 135mm lenses, and T2.4 for the 14mm lens. NiSi specifies T-stops to indicate actual light transmission, which helps you achieve consistent exposure across focal lengths when you change lenses.

The lenses also prioritize low chromatic aberration and micro-contrast control to retain finer image details. In practice, this means the 40mm is tuned to keep color fringing low while maintaining image texture and clarity.

Image circle and sensor compatibility

The Athena Primes produce an image circle of 46mm. This image circle makes the series suitable for full-frame sensors and also compatible with larger-format sensors where a 46mm image circle is acceptable. Use this lens when your camera requires that coverage for proper framing and edge-to-edge sharpness.

Mounts and the proprietary rear filtration system

NiSi offers the Athena Prime series in several mount options, and the filtration solution differs by mount:

• Available mounts across the series: ARRI PL, Canon RF, Sony E, Panasonic/Leica L, and Fuji G.
• RF, L, and G mounts include a Drop-In filter option.
• E-Mount is available in two versions: with Drop-In filter and without Drop-In filter.
• PL-mount lenses utilize a rear filter instead of a Drop-In filter.

Important: To achieve infinity focus and obtain clear images, you must use the Drop-In clear filter on RF, L, G, and E mounts, and the rear filter on PL mounts. The G-Mount 40mm in this listing is specified without a Drop-In filter installed; if your setup requires the Drop-In clear filter for infinity focus, plan to source that filter or choose the mount/version that includes it.

Also note a specific camera compatibility issue: the Sony FX9 cannot use the E-Mount version with Drop-In filters. Keep this in mind if you plan to mix mount versions and camera bodies.

NiSi also provides weather sealing for the Drop-In filter, protecting the filter element when mounted. This weather sealing applies to the Drop-In filter system rather than being a blanket statement about every surface of the lens.

Handling, mechanics, and consistency across the set

NiSi designed the Athena lenses to behave consistently across the range:

• All Athena primes (except 14mm) share the same 77mm filter thread for front filters.
• All lenses are similar in weight, which avoids the need to rebalance a gimbal when you swap between Athena lenses.
• Aperture and focus rings are matched across the series to maintain consistent hand feel and support predictable follow-focus operation.
• Both aperture and focus gears follow the standard 0.8 mod specification, making them compatible with common follow focus and matte box systems.
• Each lens has a 300° focus rotation and fluorescent focus scales in both imperial and metric units, aiding precise focus pulls and low-light visibility.

Accessories and close-focus options

NiSi offers a 77mm close-up lens (sold separately) that can reduce the minimum focus distance on Athena lenses that accept 77mm front filters. This accessory enables macro-style shots and greater subject magnification without changing lenses.

FAQ

Question: Does this G-Mount 40mm version include the Drop-In filter?
Answer: No. This listing is for the G-Mount 40mm T1.9 without the Drop-In filter installed. If your camera and workflow require the Drop-In clear filter to achieve infinity focus, you will need to add the Drop-In filter or select a mount/version that includes it.

Question: Can I use this lens on full-frame or large-format cameras?
Answer: Yes. The Athena Primes provide a 46mm image circle, which NiSi specifies as suitable for full-frame and even some large-format sensors. Confirm your camera’s required coverage to ensure full-frame edge-to-edge performance.

Question: Will I need to rebalance my gimbal when switching between Athena lenses?
Answer: Generally no. NiSi states that Athena Prime lenses are similar in weight and do not require rebalancing on a gimbal when switching between lenses in the series.

Question: Are the focus and aperture gears compatible with standard follow focus systems?
Answer: Yes. The Athena lenses use standard 0.8 mod focus and iris gears, making them compatible with most follow focus units and matte box systems used in professional filmmaking.

Question: Is the Drop-In filter weather sealed and are there any mount-specific limitations?
Answer: NiSi provides weather sealing for the Drop-In filter system. Also note that the Sony FX9 cannot use the E-Mount version with Drop-In filters. Remember to use the Drop-In clear filter on RF, L, G, and E mounts (and the rear filter on PL mounts) to achieve infinity focus and clear images.

Question: Can I achieve macro effects with this 40mm lens?
Answer: Yes. You can use the NiSi 77mm close-up lens (sold separately) to reduce the minimum focus distance and create macro-like effects on Athena lenses that accept 77mm front filters.