Sigma - difference between DG and older lenses

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Belgos - 05 Apr 2006 07:04 GMT

Hi all

Regarding the sigma 70-300 apo macro, what is the difference between the
older one made for 35mm and the new 'DG' one ? Is the fov for both changed
to the equivalent of x1.6 on dslrs ? Can the DG be used on a 35mm, and can
an older non-DG model fit the rebel xt?

Also, do extension tubes work the same way (regarding macro reproduction
ratio) when used on a dslr ? I hope I am not too mixed up.

Thanks in advance
Kostas

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John Bean - 05 Apr 2006 08:51 GMT

Sigma suffixes are confusing.

"DG" simply means it's been "optimised" for digital use -
probably just lens coatings - but otherwise it's
functionally the same as the non-DG lens and it covers full
frame as well as smaller sensors, or 35mm film.

"DC" means it can only be used with APS-C sized sensors (or
smaller) and the image circle is too small to cover a
full-frame sensor (or 35mm film).

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John Bean

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Gisle Hannemyr - 05 Apr 2006 16:50 GMT

> Regarding the sigma 70-300 apo macro, what is the difference between
> the older one made for 35mm and the new 'DG' one?

DG means improved coatings. I am not able to tell the difference,
but some people claims that DG is less prone to ghosting.

> Is the fov for both changed to the equivalent of x1.6 on dslrs?

No. The focal width remains unchanged.

> Can the DG be used on a 35mm,

Yes. All Sigma's DG lenses are FF.

Sigma uses the tag DC to designated smaller image circles, but a
Sigma DC will physically fit on a film camera (but will vignette),
while a Canon EF-S will not.

> and can an older non-DG model fit the rebel xt?

Yes.

> Also, do extension tubes work the same way (regarding macro
> reproduction ratio) when used on a dslr?

Yes. The reproduction ratio (1:1) tells you that 1 millimeter in
"real life" will measure 1 millimeter on the film/sensor. That
doesn't change even if the sensor becomes smaller. Of course, if you
were to photograph a ruler at 1:1, you would capture 36 mm of it on
film, but only 22.5 mm with a Rebel XT.

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- gisle hannemyr [ gisle{at}hannemyr.no - http://hannemyr.com/photo/ ]
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Sigma SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
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