Quick answer
The Nikon 20mm f/3.5 AI converted lens is a solid choice for film shooters who want an affordable ultra-wide manual focus prime, but you need to verify the conversion quality and condition before buying.
Why consider a converted AI lens?
Nikon's pre-AI (non-AI) lenses were made before 1977 and lack the coupling ridge that lets the camera body know the aperture setting. A conversion to AI adds that ridge, making the lens compatible with later Nikon SLRs and some digital bodies. The Nikon 20mm f/3.5 is a classic ultra-wide that originally came in non-AI mount, so finding a clean converted copy can save you money over a native AI version.
Trade-offs of buying used
Used manual focus lenses vary widely in optical and mechanical condition. The conversion itself may have been done by a third party, so fit and finish can differ. You also lose automatic aperture coupling on some modern Nikon DSLRs (those without an AI coupling tab). For film cameras like the Nikon FM, FE, or F3, a properly converted lens works perfectly.
Decision rules for buying a Nikon 20mm f/3.5 AI converted lens
- Check the conversion quality: Look for a clean AI ridge that matches factory AI lenses. The ridge should be evenly filed and not interfere with the aperture ring's movement. A sloppy conversion can cause inaccurate aperture readings or binding.
- Inspect the optics thoroughly: Wide-angle lenses are prone to haze, cleaning marks, and internal dust. Ask for a photo against a bright background. The 20mm f/3.5 has a deeply recessed front element, so scratches are less common but not impossible. If the seller offers a 90-day warranty, you have time to test the lens on your camera.
- Confirm compatibility with your camera: The converted AI lens works on Nikon film SLRs with AI coupling (FM, FE, F3, FA, etc.) and on digital bodies with an AI tab (Df, D7xxx, D8xx series). It will not meter on entry-level DSLRs like the D3xxx or D5xxx series.
- Decide if you need f/2.8 or faster: The f/3.5 maximum aperture is one stop slower than the Nikon 20mm f/2.8 AI-S. For landscape or tripod work, f/3.5 is fine. For indoor or low-light handheld shooting, the f/2.8 version is better. If you shoot mostly stopped down (f/8-f/11) for landscapes, the f/3.5 saves money and weight.
Product facts
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Nikon Nikkor-UD 20mm f/3.5 Lens Converted to AI - USED: This used Nikon Nikkor-UD 20mm f/3.5 has been converted to AI. It comes with a 90-day warranty and has been fully tested. The optics are in excellent condition with no marks, haze, fungus, or separation. The focus and aperture rings rotate smoothly. A clean conversion and smooth mechanics mean you can mount it on most AI-compatible Nikon bodies without worry, and the excellent optics give you sharp, contrasty wide-angle images.
Nikon Nikkor-UD 20mm f/3.5 Lens Converted to AI - USED
Who is this lens for?
Best for
- Film photographers using AI-compatible Nikon SLRs who want an affordable ultra-wide prime
- Landscape shooters who work at smaller apertures and don't need f/2.8
- Budget-conscious buyers who are comfortable inspecting used gear
Not ideal for
- Digital shooters with entry-level Nikon DSLRs (D3xxx/D5xxx) that lack an AI coupling tab
- Photographers who need f/2.8 or faster for low-light handheld work
- Buyers who want a modern lens with autofocus and electronic aperture control
