Leaked: Sigma 70mm f/2.8 DG MACRO | Art

ahsanford

Particular Member
Aug 16, 2012
8,617
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aceflibble said:
Internally-focusing macros have to use strong focus breathing to focus down to 1:1 (let alone beyond), and it takes a bigger toll on transmission, too. For example, the Canon 100mm f/2.8L IS Macro, when it's at absolute 1:1, is actually about 72mm t/7.4. (Give-or-take for minor copy variation and specific shooting scenario; I haven't used the EF-S 60mm or non-L 100mm to have their measurements to hand.) Of course weight and cost also go up.

Externally-focusing macro lenses can go to whatever magnification you want without changing the actual focal length, and though of course light is lost as the lens extends, it's usually not actually as much of a loss as when the lens has to shift everything around internally. That's the benefit to simpler designs like this. So this Sigma probably stays at 70mm no matter what magnification you want, and likely gets no darker than t/5 or so.

Ask, and the forum educates. Thank you for a super helpful post -- very much appreciated!

A
 

slclick

Unsolicited & Always Free
Dec 17, 2013
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Are we positive it's NOT much more than a 1:1? With the external focusing, it could be offering up more magnification.
 

scyrene

EOS R6
Dec 4, 2013
2,861
1,001
UK
www.flickr.com
aceflibble said:
Internally-focusing macros have to use strong focus breathing to focus down to 1:1 (let alone beyond), and it takes a bigger toll on transmission, too. For example, the Canon 100mm f/2.8L IS Macro, when it's at absolute 1:1, is actually about 72mm t/7.4. (Give-or-take for minor copy variation and specific shooting scenario; I haven't used the EF-S 60mm or non-L 100mm to have their measurements to hand.) Of course weight and cost also go up.

Externally-focusing macro lenses can go to whatever magnification you want without changing the actual focal length, and though of course light is lost as the lens extends, it's usually not actually as much of a loss as when the lens has to shift everything around internally. That's the benefit to simpler designs like this. So this Sigma probably stays at 70mm no matter what magnification you want, and likely gets no darker than t/5 or so.

It used to be that externally-focusing lenses also had less trouble with distortion, but these days that's mostly equalised.

All that said, I would expect the most likely reason for going for external focus is simply cost. Sigma have proven they can nail extremely demanding optics, but they are still somewhat obligated to keep their prices below first-party options. With Tamron undercutting them even further, I wouldn't be surprised if Sigma doubled down on their own penny-pinching.

That's really interesting, thanks! I've always meant to compare my 100L with the 24-105L at ~100mm to see if they differ, but now I know what to expect :)
 

Sharlin

EOS R
CR Pro
Dec 26, 2015
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Turku, Finland
slclick said:
Are we positive it's NOT much more than a 1:1? With the external focusing, it could be offering up more magnification.

This picture shows the lens at 1:1 and what appears to be maximum extension.

The nifty thing about the lens is that the inner barrel only extends as far as the lens hood (which is attached to the outer barrel). So with the hood on the external length of the lens doesn't change.
 
Mar 31, 2014
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Center of my universe
Minus: focus by wire. I don't care; if the long throw really is long.
Plus: compatible with Sigma TC's. There's that 2:1 magnification I want without sacrificing infinity focus.

Quite an intriguing lens! Maybe the one for backpacking.