ND filter for camera: how many stops your aperture needs in sun

Updated 2026-11-09 · Pick: K&F Concept ND2-400 Variable ND, 67 mm (KF01.1463): $79.99 on kfconcept.com (checked 2026-11-09): https://dealectric.com/go/kf-concept-nd2-400-vnd-67mm

Short answer. To film with a camera in full sun at 1/50 s and ISO 100, an ND filter must cut about 5 stops at f/4, 6 at f/2.8 and 7.3 at f/1.8. The K&F Concept ND2-400 variable ND reaches 8.6 stops and covers all three. A 1–5 stop ND2-32 tops out at f/4.

How this table was made: each figure comes from the maker's own US product page or manual, or from the reviewer named next to it, checked 2026-11-09. Dealectric does not test units itself. Rows with a Buy link are products Dealectric lists: the links are affiliate links, and their codes are re-tested in the brand's own cart every day (last check 2026-11-13).

What the differences mean

The figures below are worked from the sunny 16 rule (f/16 at 1/100 s, ISO 100, direct sun) and each maker's stated ND range. Prices are the makers' US store prices on 2026-11-09. For PolarPro, Freewell and Tiffen they are the lowest price each store lists for the product.

• Stops from an ND number: stops = log2(ND). ND32 = 5.0 stops, ND400 = 8.64, ND512 = 9.0. A filter labelled "ND2-400, 9 stops" really goes to 8.6.
• Stops you need for 24p video (1/50 s, ISO 100, full sun): 2 × log2(16 ÷ aperture) + 1. At f/5.6 that is 3.0 + 1 = 4.0 stops, at f/4 it is 4 + 1 = 5.0, at f/2.8 it is 5.0 + 1 = 6.0, and at f/1.8 it is 6.3 + 1 = 7.3. Each doubling of ISO above 100 adds one more stop.
• Widest aperture a filter allows in sun: 16 ÷ 2^((max stops − 1) ÷ 2). ND2-32: 16 ÷ 2^2 = f/4. ND2-400: 16 ÷ 2^3.82 = f/1.13. A 6–9 stop hard-stop VND: 16 ÷ 2^4 = f/1.0 at its darkest, and at its lightest (6 stops) it can't go narrower than f/2.8.
• Cost per stop: ND2-400 67 mm: $79.99 ÷ 8.64 = $9.26. ND2-32 True Color 67 mm: $103.49 ÷ 5 = $20.70. ND2-32 True Color 77 mm: $119.69 ÷ 5 = $23.94.

Your lens (sun, 1/50 s, ISO 100)	Stops needed	Filter that covers it
Kit zoom at f/5.6	4.0	ND2-32 True Color (67 or 77 mm) or ND2-400
f/4 zoom	5.0	ND2-32 True Color at its maximum, or ND2-400
f/2.8 zoom	6.0	ND2-400 (about ND64), or a 6–9 stop hard-stop VND
f/1.8 prime	7.3	ND2-400 (about ND160), or a 6–9 stop hard-stop VND

How many stops your aperture needs, and where a variable ND runs out

A variable ND is two polarizing layers turned against each other. Marumi says the X-shaped dark pattern near the maximum is "in principle unavoidable for all variable ND systems that use polarizing films", and that the darkening speeds up as the ring nears Max. Hoya says that near or at the maximum on its Variable Density II, the cross "cannot be eliminated". Kenko advises using its Variable ND-W "only up to ND128" (7 stops) on a 24mm lens. K&F's own X-pattern guide says the same filter can be clean at 50mm and show an obvious X at 16mm.

This is the trade-off. The K&F ND2-32 True Color stops at 5 stops, which keeps it away from the darkest setting where the X appears, so it is the cleaner choice for f/4 and slower lenses and for wide-angle work. It is also the lower-glare glass (0.1% reflectivity against 0.2%). Get $106.99: https://dealectric.com/go/kf-concept-nd2-32-true-color-vnd-67mm for 67 mm lenses, or $121.99: https://dealectric.com/go/kf-concept-nd2-32-true-color-vnd-77mm for 77 mm lenses. K&F says neither one takes a lens hood, and each needs a cap one size larger (72 mm or 82 mm).

For f/2.8 zooms and f/1.8 primes in sun, 5 stops is 1 to 2.3 stops short, and $79.99: https://dealectric.com/go/kf-concept-nd2-400-vnd-67mm is the filter that reaches them. At f/2.8 it sits around ND64, well short of its maximum. At f/1.8 it sits around ND160, close to the zone where Kenko draws its line at 24mm. That works on a short telephoto such as the Meike 85mm F1.8 SE Mark II (62 mm thread, so you need a 62–67 mm step-up ring), but watch for the X on wide lenses. Keith Cooper (Northlight Images) measured a different-brand ND2-400 at "1 to just over 8 stops" and saw "a strange cross shaped darkening" at its maximum on a wide-angle lens. K&F also notes that VND ring marks "are not necessarily calibrated as equal one-stop steps", so meter the scene rather than trusting the dial. The ND2-400's product page lists both a 67 mm and an 82 mm thread, so check the marking on the filter you receive.

If you want the X ruled out by design, PolarPro's PMVND Edition II and Freewell's Hard Stop VND use preset 2–5 or 6–9 stop ranges. Each version covers only 3 stops, so the 6–9 version can't stop down past f/2.8 in sun at 1/50 s. That makes it a fast-lens filter, not an all-day one.

Not recommended

A 1–5 stop VND as the only filter for an f/1.8 prime in daylight. At 1/50 s and ISO 100 it leaves the image 2.3 stops too bright, so you would have to stop down to f/4 or raise the shutter speed, which loses the reason you bought the fast lens.

Sources

• K&F ND2-400 67 mm: $79.99 (list $99.99), ND2 to ND400, '0.3 to 2.7 (1 to 9 Stops)', 0.2% reflectivity, 7.4 mm frame, 28-layer coating, 67 mm vs 82 mm FAQ conflict, buyer review reporting an X past the ND400 mark, 30-day refund or replacement — www.kfconcept.com
• K&F warranty policy (read 2026-11-09): 'Lens filter' standard warranty period 24 months; K&F-branded products only; proof of purchase from K&F or an authorized K&F reseller — www.kfconcept.com
• K&F ND2-32 True Color 67 mm: $103.49 (list $114.99), 1–5 stops, 'reduced X effect', 0.1% reflectivity, 72 mm cap, not suitable for lens hoods — www.kfconcept.com
• K&F ND2-32 True Color 77 mm: $119.69 (list $132.99), 1–5 stops, 82 mm cap — www.kfconcept.com
• Sunny 16 rule: f/16 at 1/ISO s in direct sun, the baseline for the stop counts — en.wikipedia.org
• PolarPro PMVND Edition II: $149.99, 2–5 and 6–9 stop versions, preset range eliminates cross-polarization — www.polarpro.com
• Freewell Hard Stop Variable ND: $109.99, ND4–ND32 or ND64–ND512, hard stop eliminates cross-polarization — www.freewellgear.com
• Tiffen Variable ND: $109.00, 2 to 8 stops — tiffen.com
• Marumi: its Creation VND combines two polarizing films; the X pattern is unavoidable in principle for all VNDs that use polarizing films; darkening speeds up near Max — www.marumi-global.com
• Kenko Variable ND-W: use only up to ND128 at 24mm — kenkoglobal.com
• Hoya Variable Density II: a cross pattern near or at MAX cannot be eliminated — hoyafilter.com
• K&F: X pattern worse on wide lenses, and a fixed ND is recommended for stronger reduction — www.kfconcept.com
• K&F: ND-to-stops chart, and VND ring marks are not calibrated one-stop steps — www.kfconcept.com
• Northlight Images (Keith Cooper): an ND2-400 measured at 1 to just over 8 stops, with a cross at maximum — www.northlight-images.co.uk
• Meike 85mm F1.8 Mark II: 62 mm filter thread (Newsshooter) — www.newsshooter.com

Published 2026-11-09; updated 2026-11-09. The buy links are affiliate links; see the disclosure. Corrections welcome at [email protected] or /feedback.