# The Saga of the Sigma 120-300 f/2.8 OS Sport



## Canon Rumors Guy (Jun 27, 2014)

```
<div name="googleone_share_1" style="position:relative;z-index:5;float: right; /*margin: 70px 0 0 0;*/ top:70px; right:120px; width:0;"><g:plusone size="tall" count="1" href="http://www.canonrumors.com/2014/06/the-saga-of-the-sigma-120-300-f2-8-os-sport/"></g:plusone></div><div style="float: right; margin:0 0 70px 70px;"><a href="https://twitter.com/share" class="twitter-share-button" data-count="vertical" data-url="http://www.canonrumors.com/2014/06/the-saga-of-the-sigma-120-300-f2-8-os-sport/">Tweet</a></div>
A Canon Rumors reader “JerseyShooter” has been working with Sigma to improve the performance with Canon’s APS-H flagship cameras, the EOS-1D Mark III & EOS-1D Mark IV.</p>
<p>Back in October of 2013, JerseyShooter started a blog documenting the issues he was having with the lens on a blog. He worked directly with Sigma and it looks like it has paid off with the firmware that was released yesterday to improve the performance with both of the mentioned cameras.</p>
<p>There have been other issues with the lens that he is documenting on the blog as well.</p>
<p>For the record, JerseyShooter is an employed professional photographer.</p>
<p><strong><a href="http://sigma120to300sportssaga.blogspot.ca/?m=0" target="_blank">Read the blog about the Sigma 120-300 f/2.8 OS Sport</a></strong></p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>
```


----------



## ScottyP (Jun 27, 2014)

Sigma is pretty smart. Bringing in people who can provide time and real world experience, and listening to the customers.


----------



## Mt Spokane Photography (Jun 27, 2014)

That's the issue with many of the lens review sites, they manually focus lenses to test their best acuity, but do not test the autofocus very well.

Third party lens manufacturers have a really difficult situation with autofocus systems. Fore example, the lens must identify itself to the camera as a particular canon lens, but canon does not make anything close to this.

Each Canon camera recognizes the lens attached from the lens code, and may make adjustments based on that information. This can cause nasty things to happen. I think Zeiss has the right idea to stay away from reverse engineering autofocus.


----------



## TheGreatOwl (Jun 28, 2014)

I just noticed an increase of the AF speed with and without a 2XIII TC... And AF motor no longer go to sleep when I'm not using it! Love this upgrade!


----------



## candc (Jun 28, 2014)

it does seem faster, especially with the 2xiii, it was already really good with the 1.4xiii as the blogger pointed out. i have noticed an issue that was also pointed out by ephotozine (i think it was them). at 120mm and around 1/200s, there is a glitch in the os. i haven't checked to see if that's been fixed?


----------

