Saturday, December 15, 2012

New DSLR sigma lens 18-105mm, very dark photographs?

Hi, I am a relatively new to photography, so please bear with me. I have been using the Nikon 18-55mm kit lens that came with my D3100.
Recently, I bought a new sigma lens, 18-105mm. However since using it, my photographs became very dark.

I shoot in aperture priority mode & in the same room with my 18-55mm lens, with an f-stop of 5.6, & ISO of 100 the shutter speed required would not be so slow, & allowed me to capture the room well lited.

But with my new lens, with the same f-stop of 5.6, the shutter speed would be about 1-2s in the same lighted room. Why is this so? Is it a camera setting or the lens? Please help me & once again, I am still relatively new to DSLR lens & equipment! Thank you! :)
>>> New DSLR sigma lens 18-105mm, very dark photographs?