First lens to buy

[ShadowUsher_26]

I have a 18-55mm lens which came with my Nikon d3500. I want to buy a lens fit for 

• Landscape photography 
• Occasional Nightscapes (Star trails or meteor showers)

And please tell me if lens sizes vary with different cameras of the same company (say nikon) because different cameras have different crop sensors?

And in case you have some extra time please explain mm of lens and other specs which one need to keep in mind while buying lenses

[RojiK]

I got a Canon 6D and love my 24-105mm f4 and starscapes and landscapes is what i like to take photos of the most

sorry i cant really explain much of it all from my head but there are always amazing youtube channels that do it well (Even a few LTT vids that do if memory serves)

[YellowJersey]

If you're rocking a Nikon DX body, I'd probably check out the Nikkor 10-20mm 4.5-5.6. What sort of budget are you working with?

[ShadowUsher_26]

About 300 to 500$

[GDRRiley]

Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary Lens

its a great replacement for a kit lens. F2.8-4 is a lot more useful than f3.5-5.6

 

I'd also add something like a used 50 or 35mm F1.8

[orso7]

You can never go wrong with a 50 equivalent (35mm for DX) wich can be had really cheap.

But I'd recommend my most loved DX lens wich I even use on FX, Nikon 10,5mm 2.8 fisheye. (~400€ used) It is special but i creates very interesting pictures in various situations. If needed the fisheye look can easily be corrected in lightroom or any other software, 24MP your camera offers should be enough for that.

 

Or you could get a used 17-55 2.8 for under 500€, that would be quite an upgrade for the kit lens. 

[kaixax555]

Get something like a Nikkor DX 10-20 f4.5-5.6. Spend the rest on a good filter kit or a solid tripod.

 

For cameras, focal length (the mm of the lens) determines how wide (or narrow) your field of view is. The smaller the mm number, the wider the field of view. The focal length determines how wide of an area you can capture or how zoomed you are in.

The f number is your aperture, it determines how big of a hole your lens can "open". The smaller the f number, the larger the opening in general. Larger opening means you can let in more light and also means you can achieve a shallower depth of field (or more background blur, which is desirable in some scenarios).

All the lenses (be it for Nikon crop sensor or full frame sensors) have focal lengths and aperture based on a full frame camera, this is because 35mm film is the standard, most lens in the past are built around this standard and this carries on to this day.

Nikon separates their DSLR lines in two, DX and FX. DX series (Nikon D3000 series, D5000 series, D7000 series, D90, D300/D300s and D500) are the crop sensor cameras, with a 1.5x crop. When you calculate the focal length and aperture, multiply both values by 1.5 to determine what you will see on a full frame camera. For example, the 10-20 DX f4.5-5.6 on your D3500 will be 15-30 f6.8-8.5.

The lens are also separated into DX and FX lines. Both DX and FX lenses can be used on corp and full frame cameras. However, DX lenses when mounted onto a full frame camera will automatically use a smaller portion of the sensor (meaning less megapixels).

But don't fret too much about the details. These numbers should not affect your creativity. Get a wide angle lens, nice filter kit, good tripod and go out and shoot.

[thermalgoop]

Since you already have the kit lens that has a decent range of focal length for your application, maybe find the distance that you use the most, and get a prime lens. If it's a cropped (APS-C size) sensor 35mm is nice. Prime lenses usually give a much crisper image, because there's less elements (pieces of glass) than in a zoom lens. You can also get a much faster lens for much less $$ in a prime lens. Sigma makes some pretty nice ones, I like my 50mm f/1.4 EF lens a lot. Although a cursory Google search looks like it may be difficult to find some of their more popular offerings new at the moment.