Sigma 70-300mm F4-5.6 APO DG Macro Lens - how do I manually focus without changing focal length?
Good day all. I have a Sigma 70-300mm F4-5.6 APO DG Macro Lens. If I turn the focus ring to manually focus the lens, the lens zooms in (or out). Surely this can't be right, is it? Is there no way to manually focus this lens without changing the focal length? I read the simple user instruction leaflet online, and it doesn't answer this. Thank you for any help!
Hi and welcome to ePz.
I think perhaps you are turning the zoom ring, not the separate focus ring which is situated further along the barrel of the lens, furthest from the camera.
Read the paragraph here, "Build & Handling" which explains closer.
I think perhaps you are turning the zoom ring, not the separate focus ring which is situated further along the barrel of the lens, furthest from the camera.
Read the paragraph here, "Build & Handling" which explains closer.
OK...in that case I'll let someone who has first-hand experience of the lens to hopefully supply the answer...
I think that you'll find that extension is caused by the lens' elements being moved to allow it to focus.
Although the lens becomes physically longer the focal length remains the same.
All lenses focus this way; it's just that in some cases, all that movement is internal.
The prime lenses that I use on my OM10, which are incapable of zoomimg, extend as they focus.
Although the lens becomes physically longer the focal length remains the same.
All lenses focus this way; it's just that in some cases, all that movement is internal.
The prime lenses that I use on my OM10, which are incapable of zoomimg, extend as they focus.
