
As I stated on this issues home page... I am not going to throw a bunch of technical stuff in the mix, since it
really doesn't matter too much since my blogs are more about
theory than trying to dish out a bunch of
facts.
In this segment, I am taking a look at the results you get from similar products in specifications but not so similar in price.
First let's look at the "
super zoom" that covers 28-300mm along with the 70-300mm
branded lens. And in this case its the Tamron SP AF28-300/3.5-6.3 XR Di LD and the Nikon AF 70-300mm f/4-5.6D ED from several years ago (not the newer VR version).
One of the things to remember is that the focal length of a lens is not some standard amongst lens makers. It basically means that at 300mm, that the
optical center of the lens is 300mm away from the camera sensor. As you will see from the resulting images here that were shot from a tripod mount in the same spot with the same camera and both at their max 300mm setting.
Right off, you will see that the Nikon 70-300 goes a bit
deeper into the scene, thus actually being a little bit
"stronger" in magnification than the Tamron 28-300.

Overall,
both images seem to be acceptable and somewhat sharp considering the distance away the trees and the house are from the camera.
Exposure was similar on both at 1/125 @ f11 set at ISO 640 with the camera setting the exposure in shutter priority mode.
The Tamron lens of 15 elements in 13 groups also has a plastic base ring compared to the metal one on the Nikon with 13 elements in 9 groups.
I noted that the Tamron lens seems to have a noticeable bit
more contrast than the Nikon lens, but be warned, that is a great way to trick you into thinking that an image is sharper. By making the contrast higher, the scenes will seem sharper, but since you typically wont
have a comparison image to look at, you wont really know if it is actually sharper or not.
Branded Lens or 3rd Party?
If the Nikon lens is really sharper than the Tamron, then a slight contrast adjustment will snap it into the brighter scene as the Tamrom appears. The reason I suggest this is after looking at the actual sharpness when zooming in to actual size of the image.

It didn't take long for me to realize that I will be selling the 28-300 most likely. I was hoping for it to be a all-in-one that I could use at Road Atlanta to capture both racing action and images from up close in the pits without having to change lens. But after seeing the difference in the quality of the pixels, I doubt I will be using the Tamron lens after all.
The detail in the yellow leaves deems to be the most noticeable, and then the detail in the stucco of the house was a bit more with the Nikon capture. And there was some
notable softness in the green leaves in the Tamron capture.
I have never been a fan of a lens with the
mounting plate made of plastic, and I am not saying that the base is the reason the Tamron lens is softer, but I am saying it is a key signal as to how much higher quality the lens will be if it is a metal base.
And I feel somewhat assured of the detail I always tell my students when they ask about gear... I always stress for them to
put the money into the glass and NOT buy a lens with the plastic mounting base.
But I
am not going to brush off the Tamron lens just yet...
until I have reviewed the image structure of a closer up capture.

While keeping the focal length at 300mm, I tilted the tripod down a bit to a building across the street from
Gallery 5. Only this time the results were a little more difficult to pick a winner from.
After comparing these to captures I am confident in my choice to NOT shoot with the Tamron. Instead you will see it on ebay soon! The way I see it... If I am gonna have a "soft" lens, then it might as well be, a Nikon lens that is a bit soft.
Not shown here are captures also using the 28mm end of the focal range and comparing it to a
Nikon 28-105mm f/3.5-4.5 AF-D. And just as in the max zoomed captures, the
sharpness of the two lens were slightly different, with the Nikon lens again being a bit more crisp than the Tamron.
None of it may even matter...
If you never had two lens's to compare or the images from them, then you would not really know there was a difference since both lens offer a very acceptable image. It's not until you
see the difference in front of you that you will possibly re-think your lens purchase. Or maybe the price point had a lot to do with your choice since there may only be
enough in budget to get the third party lens instead of the branded one.
You also may want to take into consideration the features of each lens as well.
In this case, the Tamron lens does focus quicker and easier. It also goes to 28mm and has "some" macro capability. But even taking those things in review, I still will prefer to carry the 28-105
and the 70-300 to my
photo adventures to Road Atlanta. To me, the
sharpness I give up for the one lens is not worth it, yet to many others, it may not
even matter to them. Since I print most of my works at sizes 12x18 to 24x36, I would rather have every spec of sharpness that I can get.
Maybe this isn't a fair comparison, rather than it had been also the Tamron 70-300, but the curiosity came from the idea of
replacing the use of 2 lens for 1. The specs for the Tamron 70-300 are identical to the Nikon ones, but there again, could the glass and the coatings make a difference... It appears so!