f-stop question

deb

Was with a friend last night (professional photographer) at an outside senior portrait shoot. She invited me along to be her gopher/assistant and get some practice in with my own camera. We were outside, 7:00 p.m. and I was using a Sigma DC 50-200mm 1:4-5.6 lens in aperture mode on my D3100, but the camera would not go below the f-5.6. Shouldn't it have gone down to 1.4??? What am I missing?

Would appreciate any insight!!!

dino

The F stop is the largest aperture the lens can get at each end of the zoom range. The larger aperture being at 50mm and the smaller aperture at the 200mm zoom.

I am sure you mean the lens aperture was f4 to f5.6, but with any lens when 2 F- stop numbers are given on a zoom lens they refer to the largest aperture available at each end of the zoom. So 50mm would give f4 and 200mm would give f5.6.

dfrost_1906

Yes, the big note is what Dino noted. If you are using the lens (linked here) the aperture is actually f/4-5.6 and not f/1.4-5.6.

Digital36

A f 2.8 is the fastest aperature available from any manufacturer in your zoom range and the cost goes over $1k. For outdoor portraits I would prefer f4-5.6 and you can adjust your focal/distance position to utilize your desired depth of field.