[Guest]

In the Verdict section of this review, what do you mean by "The lack of phase detection AF (on the EOS 5D II)"?



The Canon 5D II DOES have phase detection AF.



<img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/blink.gif' class='bbc_emoticon' alt=':blink:' />

[Klaus]

[quote name='colinstu' timestamp='1312795092' post='10488']

In the Verdict section of this review, what do you mean by "The lack of phase detection AF (on the EOS 5D II)"?



The Canon 5D II DOES have phase detection AF.



<img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/blink.gif' class='bbc_emoticon' alt=':blink:' />

[/quote]



If you use the EF 2x III with this lens you will not have a phase detection AF on the 5D II. Contrast detection AF will continue to work.

[PuxaVida]

[quote name='Klaus' timestamp='1312788924' post='10479']

The D3x test was about the old non-OS version-

[/quote]



oh sorry...

[mst]

[quote name='Klaus' timestamp='1312795291' post='10489']

If you use the EF 2x III with this lens you will not have a phase detection AF on the 5D II.

[/quote]



That seems to be a limitation of the lens, not the 5D II. It isn't any different on the D7000 or D3x. In fact, it's mentioned in the manual of the lens that it does not provide AF with Sigma's own 2x TC (for whatever reason).



That limitation also existed in the non-OS version (which is why I tested it with the 1.4 TC only).



Sigma generally is able to build f/2.8 lenses that AF with 2x TCs (the 70-200 zooms for example). I can only speculate why this doesn't work with the 150/2.8. Maybe it has to do with the effective aperture (with a 2x TC added, the lens is f/5.6 at large distances only).



-- Markus

[Klaus]

[quote name='mst' timestamp='1312797599' post='10492']

That seems to be a limitation of the lens, not the 5D II. It isn't any different on the D7000 or D3x. In fact, it's mentioned in the manual of the lens that it does not provide AF with Sigma's own 2x TC (for whatever reason).



That limitation also existed in the non-OS version (which is why I tested it with the 1.4 TC only).



Sigma generally is able to build f/2.8 lenses that AF with 2x TCs (the 70-200 zooms for example). I can only speculate why this doesn't work with the 150/2.8. Maybe it has to do with the effective aperture (with a 2x TC added, the lens is f/5.6 at large distances only).



-- Markus

[/quote]



f/5.6 is not a hard limit anyway though - most cameras will try to AF beyond if they don't know. However, they might have done it to assure a reasonable AF accuracy.

[Brightcolours]

[quote name='Klaus' timestamp='1312798406' post='10493']

f/5.6 is not a hard limit anyway though - most cameras will try to AF beyond if they don't know. However, they might have done it to assure a reasonable AF accuracy.

[/quote]

You can hide the 2x TC from the Sigma, which then allows the AF to function again. The camera will not throttle AF speed then either, which is not a problem in good light.



A shame the bokeh got a bit less smooth with the redesign of the optics, but for the rest it still looks like a good macro. I'd rather have the smoother bokeh than the image stabilization, though.



Also nice to see that Sigma changed that awful finish.

[youpii]

[quote name='Klaus' timestamp='1312782947' post='10476']

A ... super-apochromatic lens!

[url="http://www.opticallimits.com/canon_eos_ff/667-sigma150f28oseos"]http://www.opticallimits.com/canon_eos_ff/667-sigma150f28oseos[/url]

The bokeh could be a little better though.



Works well with the EF 1.4x III converter. The EF 2x III has its issues (no phase AF, reduced performance).

[/quote]



Thanks for the review. Nice lens indeed.

What is the closest distance that you could test with a reasonable budget?

[Brightcolours]

[quote name='youpii' timestamp='1312803121' post='10496']

Thanks for the review. Nice lens indeed.

What is the closest distance that you could test with a reasonable budget?

[/quote]

test charts are made for quite some distance. Getting a way to measure MFT at macro distances makes for really expensive targets.



I do not think there are targets designed and produced for just any distance, so this question is kind of moot?

[karlmera]

[quote name='Brightcolours' timestamp='1312791881' post='10485']

The sharpness tests are taken at a considerable distance (about 8 meters is my guess),



[/quote]



But is that logical?

[mst]

[quote name='karlmera' timestamp='1312804546' post='10498']

But is that logical?

[/quote]



Yes, if you want tests that are comparable within the whole test system.



I know you're interested in macro performance, but as Klaus already said, we simply cannot do these tests, mainly because we'd have to find someone who is able to produce a decent test chart. That chart would have to be 24x36mm in size (or maybe 48x72mm if you can lie with 1:2 MTF data) and printed at almost infinite resolution.



-- Markus