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Sigma 28-70mm f2.8 EX Aspherical DF

28_70df_1_
Review Date: Jul 7, 2010 Recommend? no | Price paid: $450.00

 
Pros:
Cons:

Hi all.

I am actually looking for some guidance on this lens. I bought it a few weeks ago as an upgrade for my kits lens (AF-S 18-135mm Nikkor f/3.5-5.6G ED DX) on my Nikon D80. While the overall results are better, I'm facing the following problems that I'm unable to understand or overcome.

Problem 1: Exposure

A. Most of my shots are underexposed by an average of 1/2 to 1 spot. And this becomes worse with higher-contrast shots. To correct it I have to use a +ve EV (of usually 0.3 to 0.7, but often even 1.0), which means I lose about a spot in speed. I use the TTL matrix exposure reading setting in my camera (Nikon D80).
B. This underexposure is also prevalent while using flash (Nikon SB-600). Again trial and error has led me to have to set the flash's EV at +1.3 to +1.7 to get the correct exposure. Again I use the TTL matrix exposure reading setting in my camera.

I have not faced this problem with my NIKKOR 70-300mm f/4.5-5.6G IF-ED VR2 lens which I have been using for over a year now. Thus, I'm wondering if there is a software compatibility issue btwn my Sigma lens and D80 body? Or am I just using it wrong?

BTW, I did get significantly better images by using manual settings of aperature and shutter; but this is NOT what I want to be doing for every shot all the time.

Problem 2: Strong chromatic aberation (CA) in the over-exposed areas of the shot.

Is this how this lens is? Or am I doing somethg wrong here? Is it linked to my "Problem 1: Exposure" above?


I've had limited experience of abt 3 yrs in using SLRs, so any guidance wd be appreciated. Thks in advance.