Want to replace 18-55 mm Kit lens for DX camera

[eric_arnold]

<p><em>The 16-85 and 18-70 don't present any advantages in passing more light for AF - they have the same maximum aperture opening as your lens.</em></p>

<p>actually, the 18-70 is 4.5 @ 70mm, while the 16-85 is 5.6 @ 85mm. i wouldn't say the 18-70 is worth switching to if you have the 18-55, though its not bad. the 16-85 has better build than the kit lens but IMO is overpriced for what you get. it's a bit sharper wide open than the kit lens but not better than the tamron, which has constant 2.8 aperture throughout the range. you can shoot the 18-55 at 3.5 @18mm, but it will be a lot sharper at 5.6 or f/8.</p>

[juanparmenides]

<p>The AF fail in low light is not always a 100 % lens issue. The Multicam has a percentage of guilty too.</p>

[jim_devlin]

I’ve had the 35/1.8 for a little over a year – it is a phenomenal lens in low-lights situations. I palyed around with the 18-55 kit lens on my D40 before that, but the 1.8 really did open up a whole new world of possibilities.

[sunilmendiratta]

<p>Well everybody is recommending this 35 1.8 lens...there must be something special about it.....</p>

[andylynn]

<p>Well, look at it this way. First, the 35/1.8 is a prime lens - meaning it can only do 35mm, but on the other hand it's very good at 35mm. It's sharp and contrasty with low distortion - optical benefits that are easier for Nikon to achieve when they don't have to worry about zooming.</p>

<p>Second, it's an f/1.8 lens. I don't know what the max aperture of the kit lens is at 35mm, but let's say 5.6 because that would make it easy. If you do the math, an f/1.8 lens lets in 10x as much light as an f/5.6 lens. Suppose there's some minimum amount of ambient light that needs to hit the AF sensor in order for it to focus. If you figure out how bright the lighting in the scene needs to be for the f/1.8 lens to focus, it needs to be 10x as bright for the f/5.6 lens to focus! It's much easier to get f/numbers like f/1.8 on a prime lens, when Nikon doesn't have to worry about zooming - the optical design is simpler and less glass is required, so it can be done cheaply. (BTW, the f/number is the bottom part of a ratio - so a smaller number indicates a larger aperture. This is counterintuitive at first. A lens with a large maximum aperture, such as f/1.4 or f/1.8, or in the case of a zoom lens f/2.8, is called "fast".)</p>

<p>The third thing that's good about a fast lens, in low light, is that if you're in a situation where depth of field requirements let you shoot at a large aperture, your ISO and/or shutter speed get a corresponding advantage. Suppose I'm shooting a person in low light, and I don't need depth of field, and I like the way my f/1.8 lens looks when used at f/1.8, and I consider 1600 the highest ISO on my camera that gives good color. So I meter my shot, it comes to 1/100 of a second, which works for me, and I shoot it. Because f/5.6 lets in 1/10 as much light as f/1.8, if I had a lens that was only capable of f/5.6 I'd have to set the shutter to 1/10, or rely on VR, or bump up the ISO, or all of the above. And I also wouldn't get the nice background blur I wanted. Which is the fourth thing that's nice about a fast lens.</p>

<p>So since the 35/1.8 combines those advantages with being pretty inexpensive ($200) and having AF-S, and being a focal length that's useful on a DX camera (the field of view is similar to a 35mm film camera with a 50mm lens, which is what most of us learned on) it's a fan favorite.</p>

[randyhargraves]

<p>If by "fail", you mean it fails to achieve autofocus due to the low-light, then that's not really a lens problem. If you're trying to focus on a object near to the camera, be sure the AF-assist lamp is turned on. You could definitely achieve better low-light performance with the 35 f/1.8, but the D5000 won't autofocus in the dark without the AF-assist lamp. The 18-55 is very sharp but it's rather slow and the 5.6 aperture doesn't help you in that situation either. Try the assist lamp and if that doesn't work then consider getting a fast prime like the 35 or 50 1.4 G.</p>