[PT1]

I recently asked Sigma whether there was a technical reason why the 24-105 F/4 (a full frame lens) couldn't be sold for Pentax? (I currently have the 18-250 Macro on my K-3)

The answer was that there's a shortage due to worldwide demand, but once they are able to fulfill the demand for the current mounts, releasing for Pentax would be contemplated, but not guaranteed.


Usefully, dpreview have reviews for both the 24-105 and the 18-250 Macro on an EOS 7D:
Lens reviews update: test data for the Sigma 24-105mm f/4 DG OS HSM: Digital Photography Review
Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM review: Digital Photography Review

MTF-50 sharpness at 24mm (24-105) and 28mm (18-250):
Approx 1875 (centre) to 1530 (corner) for the 24-105 at f/5.6
Approx 1500 (centre) to 1300 (corner) for the 18-250 Macro at f/8.
Approx 25% centre improvement, 18% corner improvement.

MTF-50 sharpness at 35mm:
Approx 1800 (centre) to 1550 (corner) for the 24-105 at f/5.6
Approx 1500 (centre) to 1300 (corner) for the 18-250 Macro at f/8.
Approx 20% centre improvement, 19% corner improvement.

MTF-50 sharpness at 80mm:
Approx 1700 (centre) to 1375 (corner) for the 24-105 at f/5.6
Approx 1500 (centre) to 1130 (corner) for the 18-250 Macro at f/8.
Approx 13% centre improvement, 22% corner improvement.

MTF-50 sharpness at 105mm: (interpolated approx between 80 and 135 results for the 18-250)
Approx 1600 (centre) to 1375 (corner) for the 24-105 at f/5.6
Approx 1440 (centre) to 1070 (corner) for the 18-250 Macro at f/8.
Approx 11% centre improvement, 29% corner improvement.


The EOS 7D is 18 Megapixel, rather than approx 24 Megapixel for the K-3, but hopefully the sharpness improvement scales between the two cameras?

If so, I'd say it's worth the upgrade to buy the 24-105 for my K-3, if or when they make it. (Ok, it heavy, equivalent to approx 36 to 158mm on the 1.5x crop factor K-3, and needs 82mm filters, but it's impressive!)

And it might perform even better on a full frame camera? (The 22.3 Megapixel full-frame 5D mk3 alternative is selectable in the review, with an MTF-50 up to 2500)

[zeds]

I think Sigma 24-105 is good.
that's really my style..hehehe

[klaus123]

This is my candidate for the first full frame Pentax ( in case I follow that way)

[rawr]

You might add this DxOMark comparison of the two lenses on a 7D to your study list.

[PT1]

Thanks, and of course Best zoom lenses for the Pentax K-3 - DxOMark

And http://www.dxomark.com/Lenses/Ratings

[Parallax]

This has nothing to do with the K-3. Moved to the proper forum.