First a small overview.
The Nikkor 40mm comes with a f2 aperture and a 52mm filter thread. It’s the most compact native lens for the Z system. There’s also a 28mm f2.8 which shares the size, build quality and filter thread and the 26mm f2.8 pancake which is even smaller but costs more than twice of the 28 and 40 lenses.
What I like
Size and weight: at 170 g/6 oz it feels like air in your hands. Attaching it to the camera doesn’t really change the feeling of weight, it only adds a bit more balance to the front. The lens is barely longer than the camera's grip which makes a nice compact combo.
This lens is sharp. No questions about it. In fact probably any modern lens will be shapr. I didn’t check “corner to corner” sharpness but never have I thought to myself “oh this isn’t as sharp as it should”
F2 has plenty of light. Of course if you need more for a specific project or assignment then you need more but for most of scenarios this is plenty of light
Now the thing that really sets it apart from other lines of native lenses is its price. At amazon US I see the price is $226.95 which is at least half of any other alternative. In fact the second cheapest native prime (except the 28) will be the 26mm which is priced at $416.95. Then the 50mm f1.4 prime is priced at $546.95. You see what I’m getting at. The 28mm and 40mm are the cheapest native options.
What I don’t really care about but can be a deal breaker for you:
There are no custom buttons or extra customizable rings on the lens. If that is something you’re using on an everyday basis then this might not be for you.
No weather sealing. The lens provides zero weather resistance against rain. Personally it doesn’t bother me at all. If I’m going to shoot in the rain I’ll use a different lens or at least equip myself with an umbrella or even some extra plastic wrap around the camera.
Plastic mount. The biggest build quality con I can think of is that it has a plastic mount. However, after nearly 2 years of using it and swapping regularly with other lenses I see no wear or tear and the lens fits tightly in the camera mount. At the same time, this is one of the things that makes it so light and, let's be honest, also affordable. If this is a big deal to you, and you’re not afraid of DIY modifications, there are tutorials on how to replace the lens mount with a metal one. Personally I see zero need to do that, as it doesn’t bother me at all.
Summary
So based on all of the above, why do I think the 40mm is the must have lens and not the 28mm? The build quality and everything else is exactly the same but the 40mm I feel is a more versatile lens. It sits exactly between 35mm and 50mm which are my favourite focal lengths and is perfect for street or travel photography. Of course you can also get the 28mm if that’s your thing. Any of these two lenses is a must have for the Nikon Z system in my humble opinion.
