laugh at a newbie time

[arthurking83]

What model is your Sigma fillum?

I've used the Tammy 90/2.8 and the Sigma 150/2.8, and on Nikon cameras they indicate the 'correct' aperture when focused closely.

Roughly about the same values too .. around f/4.8 to something like f/5 or so.

[Rattus79]

Just to add to Arthur's post, lens specifications are generally rated when focus is at infinity. At other focus distances those specifications might not apply. In macro lenses generally the focal length increases as the magnification approaches 1.0x (1:1). So even though the physical size of the aperture doesn't change, the "f-number" increases because the focal length increases (since f-number = focal-length / aperture-diameter).

For example my Nikkor 105mm f/2.8D won't go faster than f/5 at closest focus distance (1:1). I also have a Sigma macro 105mm f/2.8 but it shows f/2.8 at minimum focus distance (1:1), however both lenses show almost the same shutterspeed for the same scene / lighting even though the reported f-numbers are almost two stops different.



Cheers.

That was somthing I did not know! I think the key term here is the "reported" F=numbers.

[Redback200]

More importantly then working out how the lens works. How have the pictures turned out?