Equipment & Techniques > Cameras, Lenses and Shooting gear
Sigma 2.8/70 Macro for Infinity?
Hening Bettermann:
A question to you who use this lens (at infinity).
Photozone has tested it at infinity (only) with very good results for optical quality. However, looking at a picture of the lens, I see that there is very little space between the 1.5 m and the infinity marks on the barrel. Could it be that the pitch of the focussing thread makes the lens unsuitable for manual focussing in the infinity range?
edit:
on
http://www.imaging-resource.com/lenses/sigma/70mm-f2.8-ex-dg-macro/review/
I read
"The manual focus ring has PLENTY of travel, permitting very accurate manual focussing".
Hm...strange...
Yet another question:
Imaging-resource states "Nikon and Pentax mount lens do have no aperture ring, therefor depending on camera model some functions may not work." this seems to say, in reverse, that Canon mount specimen do have an aperture ring, but I have not seen any on any of the images of the lens I have seen anywhere. How would you set the aperture when the lens was adapted to an a7r2?
TeeKay:
--- Quote from: Hening Bettermann on May 22, 2016, 06:17:32 pm ---Could it be that the pitch of the focussing thread makes the lens unsuitable for manual focussing in the infinity range?
--- End quote ---
Not from my experience.
Why would you focus manually in the infinity range instead of using AF, though? Manual focus is very useful for macro distances, but at infinity using AF seems to be the easier option.
--- Quote from: Hening Bettermann on May 22, 2016, 06:17:32 pm ---Yet another question:
Imaging-resource states "Nikon and Pentax mount lens do have no aperture ring, therefor depending on camera model some functions may not work." this seems to say, in reverse, that Canon mount specimen do have an aperture ring, but I have not seen any on any of the images of the lens I have seen anywhere. How would you set the aperture when the lens was adapted to an a7r2?
--- End quote ---
I believe the lack of an aperture ring for Nikon and Pentax was mentioned because respective lenses for these brands often have aperture rings.
Canon EOS lenses, on the other hand, don't have aperture rings, so you won't find one on the Sigma 70/2.8 for Canon either.
There is trick how you can still stop down Canon lenses and there might be adapters that support stopping down:
video
Hening Bettermann:
Hi TeeKay,
thanks for your reply.
wrt focussing:
I would not use the lens on neither Canon nor Nikon, but adapted to an a7r2, so the AF won't work anyway. And even if it would, I would not use it. As a landscaper, I use manual focus. When the (absence of) wind permits, I use focus stacking, which will not work with AF at all. My concern is, that the travel on the lens barrel for manual focussing seems very little.
wrt stopping down:
So I would need an adapter with an iris, and still, it wouldn't have an f-stop scale, since the scale would have to be specific for the focal length. I see that such adapters have a generic scale or just no scale. And there are other concerns with an iris placed outside the lens - vignetting and defraction.
So this seems to be a no-go.
Hening Bettermann:
Well, in the meantime I have acquired not a 70 mm Sigma macro, but an Apo Lanthar 125 and 180, and I am now in the position to answer my own question:
Yes the short focus throw makes these lenses unsuitable for (my) infinity work with focus stacking. I have glued a cm/mm scale around the lens barrel to get repeatable focus settings. The 2 screen shots show 2 attempts of reproducing "12.98" mm on that scale, where 13.0 mm is infinity, according to the physical stop on the lens. Apo Lanthar 125, crops @100%.
And it gets worse.
Still looking for a good lens in the 70 mm range, I even dared to look at various varieties of the 75 mm Elmarit. As far as I can infer from images of these Elmarits, comparing their distance scale to that of my 85 mm Sonnar, I see that the Elmarit has a much shorter focus throw - and that's not a macro lens!
So, the focus throw is a feature to look for when buying a lens - one that seems to get little awareness.
If anybody knows of a good 70 mm lens with a looong focus throw, as the Zeiss lenses, I'm all ears.
Good light! - Hening.
kers:
--- Quote from: Hening Bettermann on May 29, 2016, 07:39:42 am ---... As a landscaper, I use manual focus. When the (absence of) wind permits, I use focus stacking, which will not work with AF at all. ...
--- End quote ---
I like to use focus stacking with AF lenses-
the good thing is:
i use a camranger... and my iPhone to control it.
I do not have to touch the lens during the stack...
I can make a stack serial automatically...
a good 70mm;
i do not know but there are a lot of good 85mm lenses... Sony has made one just now...
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