At the advise of others on this forum, I have purchased a Sigma 50-500mm Zoom Lens for use on our Red-One. It is a beautiful lens in mint, like new condition. This is the model without the OS and with an aperture ring for external control.
Since other Red owners have used this lens, I just want to make sure you guys are having the same issues I'm having with it. Therefore, my question is this:
I have owned or used many, many lenses in my life, but never one quite like this. It was obviously designed for still use, but most others made for still cameras do not have these restrictions.
This Sigma lens does NOT hold focus throughout the zoom range. In other words, when focused on the subject at full extension, as you zoom back it goes in and out of focus. No, it is not the back focus adjustment on the camera lens port. As such, this lens can only be used theoretically as a series of fixed lenses and has to be focused at each separate focal length.
If this is normal for this lens, then so be it, and I can live with it. I was hoping I could use it as a zoom lens as well though, but if not, OK. It would be more like having many different lenses all in one.
Another thing I noticed. Most zoom lenses, when an object is too close, you just can't focus on it. But, with this Sigma it "jumps" out of focus when it's past the zoom range it can handle. For instance, it will focus at 300mm, but as soon as you've passed that, to 350mm or beyond, it "immediately" goes super-soft.
Are these things typical of this lens? Is it just the norm because of the design?
If you have any knowledge and experience with this lens I'd appreciate knowing if you have the same issues.
Thanks for your time.