Tamron 28-75mm pictures are not clear why?

i recently picked up this lens for my XTI body and ive been noticing all my pictures are not coming out as clear as i thought it would be

its not the focus but its just really grainy at any iso 400 or 1600
i dont understand what the problem it
my 18-55 is more clear and less grainy

can some help me on this?

examples?

i seem to be having this sort of problem with night or dark pictures

I'd return it and get the Tamron 17-50 instead. It's much sharper.

2 more

A lens doesn't generate noise... so it's something else.

The problem with downsizing for web is that it, pretty much, removes/masks the effect of "noise". Images, downsized will always look much cleaner.

In your firat picture, change the color balance and you'll probably notice things improve.

The second shot looks fine. Post a part of it at 100% to get a better idea of the noise.

Also, did any of these shots get post processed such as increasing the exposure because the untouched iages were too dark ? That will also increase/emphasize noise.

At 1600 they're going to showe noise, no matter how well the image is exposed.

SnapLocally.com wrote in post #6912136
I'd return it and get the Tamron 17-50 instead. It's much sharper.

But it doesn't go to 75, if that is important to you. It is for me... I never considered any of the 1n-5n lenses.

A lens may not generate noise per se, but you'll have noisier images using a zoom than a prime, I'm guessing due to more optical elements.

I didn't miss the last 25 mm in the least. They sucked on the 28-75 anyhow. Conversely, the first 11 mm was a much welcomed change.

The Tamron 28-75 is a sterling performer, and it has somewhat better MTF ratings in testing than the newer Tamron 17-50mm!

As someone stated, lenses do not create noise. Noise is a digital reproduction artifact only.

I'll be honest... I don't really see what the problem is. Could you give us a comparison shot between your 18-55 and your tammy?

SnapLocally.com wrote in post #6912136
I'd return it and get the Tamron 17-50 instead. It's much sharper.

Actually, it isn't. Just a different focal length.

SnapLocally.com wrote in post #6912220
I didn't miss the last 25 mm in the least. They sucked on the 28-75 anyhow. Conversely, the first 11 mm was a much welcomed change.

I must have an exceptionally bad copy, too.
Tamron 28-75mm at 59mm FL, hand held 1/60 f/6.3 ISO400, shown at 100% crop.

I don't see any thing wrong with your samples. They are all taken at night it looks like. Just because you get a fast lens does not mean your pictures are going to turn out all the time. What do they look like taken during the daytime when there is light?

We are talking an XTI at 400 plus ISO. I don´t see a problem here.
The 28-75 is a great lens and you will probably find it sharpest at F8. But in low light that means higher ISO.
It´s not a pro lens afterall but bang for buck it is good my only issue with Tamrons are how slow to focus they are.

Comparing my 28-75 against the Canon 24-70L the only advantages to the Canon I saw were build and focusing....the images were indistinguishable.