Few questions about Nikon 50mm and 85mm

[goodguy]

I am in a place where I love me long telezoom (70-300mm VR) and my "go to" lens (24-85mm VR) and I have been looking closer at my nifty fifty 50mm 1.8G.
Back when I still had my D7000 it was never very sharp, in portrait on 1.8 the eyes (I always aim to the eyes in portraits) came out soft, I thought it was my D7000 so I didnt make much of it but now with my new D7100 I dont see a whole lot improvement.
Its ok but not crisp and sharp as I excpect a prime lens to be, its actually not as sharp as my 24-85mm VR.

I hear a lot of good feedback on the 85mm lens, how sharp it is and perfect of portrait so I wonder how true is it ?
I am not talking about the 85mm 1.4G, thats an expensive lens out of my league, I am talking about the 85mm 1.8G or the 85mm 1.8D.

How sharp are they really (especially compared to the 50mm 1.8G), is there any difference ?
Is there any sharpness differences between the 85mm 1.8G or D models ?
The "D" is cheaper so is it worth buying over the "G" ?

 

[KmH]

Few consumer grade prime lenses focus sharply when used with the aperture wide open.
To reach the beginning of their sharp focus aperture range they need to be stopped down 2 stops or more.
F/3.5 is 2 stops smaller aperture than f/1.8.

Your 24-85 mm VR is already stopped down to f/3.5 when used wide open.

Nikon Nikkor AF-S 50mm f/1.8G review | Cameralabs

With fast lenses, a fair amount of the edges of the lens elements are used and the glass is thinner out there and causes the light to focus at a slightly different distance than the middle of the glass does.

Lens makers use correcting lens elements to compensate, but to do a really good job requires higher grade glass and more correcting lens elements.
That makes a lens cost more and puts it in the prosumer or pro glass category.

You can get a good idea in advance of buying a lens by looking at it's MTF chart, and if available looking at the lens element layout inside the lens.
NikonUSA.com has both available and some review websites, like DPReview.com publish their own MTF charts.
(MTF = Modulation Transfer Function)

Camera Lens Quality: MTF, Resolution & Contrast

 

[Derrel]

The 85mmm f/1.8 AF-S G is the second-sharpest lens tested at DxO Mark, out of I believe, 72 different lenses in F-mount. #1 is the Nikkor 85 1.4-G, #2 the 85-1.8-G, #3 the Sifma 35mm 1.4 HSM.

I own a lot of Nikkor lenses, some of them quite good; the 85/1.8 G has the performance level I would expect of a $1,500 lens. The 50mm 1.8 AF-S G is good, but not nearly so remarkably so.

 

[Derrel]

Look at this 85mm lens comparison: the 85mm 1.8 AF-S G series Nikkor offers the most-consistent performance of all the tested lenses. Nikon 85mm comparison review | Cameralabs

In terms of bokeh, and chromatic aberration, the 85mm 1.8 AF-D is a clear LOSER. Don't bother with it. Period. Especially now that we are in the 24- to 36-megapixel, high-rez era.

 

[goodguy]

Few consumer grade prime lenses focus sharply when used with the aperture wide open.
To reach the beginning of their sharp focus aperture range they need to be stopped down 2 stops or more.
F/3.5 is 2 stops smaller aperture than f/1.8.

Your 24-85 mm VR is already stopped down to f.3.5 when used wide open.

Nikon Nikkor AF-S 50mm f/1.8G review | Cameralabs

With fast lenses, a fair amount of the edges of the lens elements are used and the glass is thinner out there and causes the light to focus at a slightly different distance than the middle of the glass does.

Lens makers use correcting lens elements to compensate, but to do a really good job requires higher grade glass and more correcting lens elements.
That makes a lens cost more and puts it in the prosumer or pro glass category.

You can get a good idea in advance of buying a lens by looking at it's MTF chart, and if available looking at the lens element layout inside the lens.
NikonUSA.com has both available and some review websites, like DPReview.com publish their own MTF charts.
(MTF = Modulation Transfer Function)

Camera Lens Quality: MTF, Resolution & Contrast

Look at this 85mm lens comparison: the 85mm 1.8 AF-S G series Nikkor offers the most-consistent performance of all the tested lenses. Nikon 85mm comparison review | Cameralabs

In terms of bokeh, and chromatic aberration, the 85mm 1.8 AF-D is a clear LOSER. Don't bother with it. Period. Especially now that we are in the 24- to 36-megapixel, high-rez era.

Thank you both guys for the info.
I took few shots in F3.5 of my family members and the improvement is negligible, I think I either got a lemon of a lens or I found the limitation of the lens and this lens simply limits me.
Darrel thank you for recommending me the G model and warning me from getting the D, I don't want a copy of my current 50mm, I want the sharpest lens I can get for the money for portraits and other close shots where the DOF is shallow and the lens really needs to work hard to get those sharp, crisp shots I am looking for.