Tamron SP 45 mm f/ 1.8 Di VC USD Lens

Extremely well built
Extremely Sharp
1.8 Maximum Aperture
Vibration Compensation

Weaknesses:

Some (but very little) chromatic abberation at the far corners and extreme sides.

Comments:

I often wondered if the rumors were true about 45mm being closer to what you see normally.  While using this lense, I have to say that may be true.

This lens is simply superb and very comparible to many of my Nikkor primes.  If you do not get sharp images with this lense, you are doing something wrong.  I just decided to purchase a second one.  I REALLY like this lens.

The autofocus is quick and fairly silent.  In fact the AF sound is quieter than some of my Nikkors.  Want to manual focus?  Grab the focus ring and do that while holding your AE/AF - Lock programmed key.

I noticed right off that this is a larger lense than others I have in this focal length.  Larger elements in the rear of a lens is the way to produce better images.  My guess is that vignetting improves because the circle of confusion is better adjusted with larger rear elements.  Tamron is getting quite good at building lenses.

There are switches provided for VC on/off and AF/Manual focus.  It took me a little while to find them without taking the camera from my eye, but it's no problem now.  I guess I should mention it's a little tricky, but it works.

Images are sharp, crisp and contrasty with normal settings, and colors pop.  There is a tiny bit of distortion when you get close to a subject, but DXO and Perfectly Clear take care of it.  I am thinking of using this for landscape and architecture all the time now.

I now have two of these and one is on my D850 at all times.  I shoot a lot of small group shots and the sharpness is unbeatable.

Overall very good build qualIty, excellent fit and finish, and quite nice image quality. Image stabilization in a "normal" focal length lens is virtually unheard of, and it works quite well. Bokeh is round and quite smooth. Sharpness wide open is respectable and improves up through about f/4. Vignetting is prominent but easily corrected in post processing (or not, because it actually looks cool). Contrast and color rendition are what I could call "standard". 

Weaknesses:

Chromatic aberration is the weakest point on this lens. It is easily controlled in Photoshop or Lightroom, however, and doesn't pose a major issue.

Comments:

45mm might seem like an odd focal length, but Tamron claims it’s the closest angle of view you can get to how a human actually sees the world (on a full-frame sensor). And I agree that it does feel a little bit more “natural” than either 35mm or 50mm focal lengths. It’s not dramatically different, but it’s pretty good marketing on Tamron’s part.

Overall, this is a solid lens. It’s very well built (it’s comfortably heavy), has weather sealing, offers vibration compensation (image stabilization), and has a respectably fast f/1.8 maximum aperture. It just feels robust and has a great look. Image quality is very nice as you will see in the sample photos.

I have a full review with image samples posted here: http://tightcamera.com/tamron-sp-45mm-review/