Question: Sigma 120-400mm lens?

Hi folks,

I just checked my Sigma 50-500mm f4.5~6.3 lens. The wide open aperture is f4.5 from 50mm to about 80mm, f5.6 from about 80mm to about 280mm, and f6.3 from about 280mm to 500mm.

Can someone that owns the Sigma 120-400mm f4.5~5.6 APO OS HSM tell me at what focal length the wide open aperture switches from f4.5 to f5.6?

Thanks.

Ron

hello,

i have a sigma 120 -400 and it switches from f4.5 to f5.6 at 210.mm.

simosvak said:

hello,

i have a sigma 120 -400 and it switches from f4.5 to f5.6 at 210.mm.

Click to expand...

Thank you very much.

Ron

Ron, at the point the lens switches from one displayed aperture to another does not mean that is the point that it actually switches. The displayed aperture value switches at the point in which the real aperture is closer to one displayed value than the next one. So when it switches from say F4.5 to F5.6 it switches when the actual aperture is like around F5 (but Pentax can't display F5). It is easier to see the real switch point when you look and see when the shutter speed changes. That is determined by actual light not the value displayed. The camera aperture table can't dsiplay all possible values down to 1/3 of an aperture. Some they leave out, especially ones that are not important to their own line of lenses (saves firmware space). I did a study on this about 2 decades ago on the Pentax-Discuss Forum.

Kent Gittings

At 210mm the lens is actually at F5 but Pentax cameras usually don't have that value in memory. If it was a Canikon lens it would display F5 at that point. The display value switches from F4.5 to F5.6 when the actual aperture is closer to F5.6 that F4.5, which is an actual aperture of approximately F5.

Kent Gittings

I use a 120-400 quite a bit, on K10,K5 and now the K3. I just took some test shots to see what I could see. It changes from f4.5 to f5 at 140 mm and from f5 to f5.6 at 210 mm. It shows this in the view finder as well as the top lcd on the K3. Ken am I missing some thing.

serve

brandrx said:

Hi folks,

I just checked my Sigma 50-500mm f4.5~6.3 lens. The wide open aperture is f4.5 from 50mm to about 80mm, f5.6 from about 80mm to about 280mm, and f6.3 from about 280mm to 500mm.

Can someone that owns the Sigma 120-400mm f4.5~5.6 APO OS HSM tell me at what focal length the wide open aperture switches from f4.5 to f5.6?

Click to expand...

My thought process in the above question was that I was thinking that the Sigma 120-400mm f4.5~f5.6, because of it's aperture from 210mm to 400mm being f5.6, might be just a tad better for all around shooting than the Sigma 50-500mm lens.

I had a crazy notion that I might purchase one of those Sigma 120-400mm lenses, then a little birdie told me to wait to see how the Ricoh/Pentax 150-450mm FF lens turns out first.

Ron