Problem with a Sigma 24-70mm f/2.8 on a DX body

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Klangsty
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Problem with a Sigma 24-70mm f/2.8 on a DX body
3 months ago

Hi, folks. I'm kinda new here and new to the DSLR world, so please bear with me. If I don't include enough information, just let me know and I'll try to clarify.

I own a Nikon D3100 and have a kit 18-55 lens, and a nikkor 50mm f/1.8. Sometime in the distant future I plan to get an FX camera body, so when I started looking at a 24-70mm f/2.8, I didn't hesitate to add it to my wishlist on Amazon, because I knew I could use it on my DX body, and could continue using it when I upgrade later on.

There was no way I could afford the Nikkor version of this lens at $1.8K, but I did find good reviews on the Sigma version. Last week, I won a bid on ebay for this lens, from a reputable seller and photographer. At $400, it was a steal. Everything is in GREAT condition from what I can see, but I'm having some trouble with exposures on this puppy.

Before I leave feedback for the seller or ask to return it, I wanted to make sure it wasn't something I was doing. I've figured out that I am unable to use the autofocus because my body doesn't have an AF motor- an amatuer mistake, but I learned! And I know that FX lenses crop frames on a DX body- I'm fine with that in the meantime. But why are my pictures SO underexposed with the same settings I use on my kit lens?

Here's an example. The decent exposed picture is with my kit lens, and the darker image is with the Sigma 24-70. This was the "correct" exposure on my kit lens, but showed waaaay under exposed on the Sigma.

Thanks in advance for your help!

Taken at 35mm on both lenses

f/: 5

Shutter: 1/8

ISO:100

 Klangsty's gear list:Klangsty's gear list
Nikon D3100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 18-200mm f/3.5-5.6G IF-ED VR Nikon AF-S Nikkor 50mm f/1.8G
Nikon D3100
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