What lens would be the closest equivalent to a 50mm from a 35mm camera on my Nikon D90?

From what I understand, it would be a 35mm or 40mm lens correct? I know the sensor isn't a full format. I miss being able to "zoom in with my legs" and do more close up shots. The standard mini-telephoto that came with the camera when I got it doesn't allow me to do it as well. Part of the problem is that it is a wide-angle lens. I like taking close ups of things for texture (like starfish on a beach), so would a 50mm-equivalent lens be sufficient, or should I consider getting a macro-lens as well?

Also, is Nikkor or Sigma still considered some of the better brands for lenses? I haven't bought camera equipment in quite a while…

Added (1). I know that Nikkor is made by Nikon. I have a bunch of lenses with my old FE. That is what I used all throughout high school. I think I have the 18-105mm lens. It is what came with the camera. Would you suggest a different second lens because I have the 18-105?

Added (2). Nevermind my comment about the 18-105mm lens. I read that wrong. I thought you were saying I should buy that instead of the 35mm. I DO have the 18-105, so I'm looking for a second lens that will be good for some macro stuff and traditional photography.

Added (3). The things I like to shoot:
Landscapes
Portraits in landscapes
Still life sorts of things

I really like all my stuff in super sharp focus, so a large depth of field is a plus.

What other details could I include?

1.5X 35 = 52.5

Nikon makes a fantastic 35 1.8 dx that costs less than 200 bucks.

If you don't have an 18-105 kit lens, you should consider buying one…

Nikkor lenses are made by Nikon.

Update - Yes, the 18-105 is the standard kit lens for the 90. Tell us what you like to shoot and we can recommend lenses for you.

Landscapes - Tokina 11-16 2.8 and a heavy tripod
Portraits - 50 1.4 AF or AF-S
Closeup work - 40 or 105 macro

There's an apparent focal length shift when using the 50mm lens; or any lens for that matter - on a crop DSLR. This is true whether the lens is a FX or DX lens.

The crop factor on the D90 is 1.5, so you can multiply any lens by that to get the 35mm equivalent. This is usually refereed to as the "effective" focal length.

But if you are wanting a lens to look like a 50mm lens, you are assuming a 35mm lens would work fine. While the 35mm lens would indeed "appear" to be a 52mm lens, remember that it is still a 35mm lens and will have the same small amount of perspective distortion a 35mm lens has that the 50mm lens does not have… Because it is a 35mm lens.

I also own a D90, and for that reason, I do not like the 35mm lens, and still prefer the 50mm, even though it means I have to back up a bit to get the equivalent of a 50mm lens on a full frame or 35mm camera.

There's too much controversy over the crop factors. If you keep it simple, and look at it like this, you will be ahead:

Putting a lens on a crop factor camera vs.full frame (35mm) camera has the same effect as simply having to back up with the crop factor camera to get the same size objects in your photo. So to get the full frame (35mm) equivalent in a lens, you can basically zoom backwards with your feet.

That then means a lens is a lens, and will retain the same characteristics whether or not it is used full-frame or cropped. Too many people think using a lens on a cropped camera means it takes on the characteristics of the new focal length, but it does not.

If you want closeups, by all means consider a macro lens.

Sigma is a 3rd party lens manufacturer, and I consider the quality of lenses to be in this order - of descending quality:

Nikon #1
Tokina #2
Sigma #3
Tamron #4

There may be those that disagree with me, and I only own Nikon and Tokina lenses. I might consider a Sigma if it is the right lens, but I have absolutely no interest at all in Tamron lenses.

The 35mm 1.8 DX is a 'normal' prime lens for cropped sensors. It is a really good lens for general purpose photography.

If you want to do closeups, you need either a telephoto or a macro (Nikon calls them 'micro') lenses.

Unless you are photographing very small objects, a modern telephoto zoom will focus close enough to capture things like insects, flowers, and the like. Your 105mm lens would probably do alright at the 105mm setting… Simply back up enough so it can focus. I use my 70-300mm lens for this all of the time and it is superb.