Here are some comparison shots using a 1Dmk2 with 1.3x crop factor.  <hr><br><Br>

<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 16mm Corner Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 16mm</td>
<TD>Sigma 12-24mm f/4.5-5.6 @ 16mm</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2942.JPG">
<br>Canon @ 16mm f/2.8 </TD>
<TD>N/A
<br>Sigma @ 16mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2943.JPG">
<br>Canon @ 16mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2948.JPG">
<br>Sigma @ 16mm f/5</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2944.JPG">
<br>Canon @ 16mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2949.JPG">
<br>Sigma @ 16mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2945.JPG">
<br>Canon @ 16mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2950.JPG">
<br>Sigma @ 16mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2946.JPG">
<br>Canon @ 16mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2951.JPG">
<br>Sigma @ 16mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2947.JPG">
<br>Canon @ 16mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2952.JPG">
<br>Sigma @ 16mm f/16</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2947a.jpg">
<br>Canon @ 16mm f/16 with Photoshop CS Chromatic Aberation correction (shot raw) </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16corner/HP8F2952.JPG">
<br>Sigma @ 16mm f/16</TD>
</TR>

</table><br><br><hr>


<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 16mm Center Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 16mm</td>
<TD>Sigma 12-24mm f/4.5-5.6 @ 16mm</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2942.JPG">
<br>Canon @ 16mm f/2.8 </TD>
<TD>N/A
<br>Sigma @ 16mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2943.JPG">
<br>Canon @ 16mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2948.JPG">
<br>Sigma @ 16mm f/5</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2944.JPG">
<br>Canon @ 16mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2949.JPG">
<br>Sigma @ 16mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2945.JPG">
<br>Canon @ 16mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2950.JPG">
<br>Sigma @ 16mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2946.JPG">
<br>Canon @ 16mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2951.JPG">
<br>Sigma @ 16mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2947.JPG">
<br>Canon @ 16mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/16center/HP8F2952.JPG">
<br>Sigma @ 16mm f/16</TD>
</TR>

</table><br><br><hr>












Here are some comparison shots using a 1Dmk2 with 1.3x crop factor.  <hr><br><Br>

<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 20mm Corner Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 20mm</td>
<TD>Sigma 20mm f/1.8 @ 20mm</TD>
</TR>


<TR>
<TD>N/A
<br>Canon @ 20mm f/2 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2959.JPG">
<br>Sigma @ 20mm f/2</TD>
</TR>


<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2953.JPG">
<br>Canon @ 20mm f/2.8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2960.JPG">
<br>Sigma @ 20mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2954.JPG">
<br>Canon @ 20mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2961.JPG">
<br>Sigma @ 20mm f/4</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2955.JPG">
<br>Canon @ 20mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2962.JPG">
<br>Sigma @ 20mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2956.JPG">
<br>Canon @ 20mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2963.JPG">
<br>Sigma @ 20mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2957.JPG">
<br>Canon @ 20mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2964.JPG">
<br>Sigma @ 20mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2958.JPG">
<br>Canon @ 20mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20corner/HP8F2965.JPG">
<br>Sigma @ 20mm f/16</TD>
</TR>

</table><br><br><hr>


<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 20mm Center Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 20mm</td>
<TD>Sigma 20mm f/1.8 @ 20mm</TD>
</TR>



<TR>
<TD>N/A
<br>Canon @ 20mm f/2 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2959.JPG">
<br>Sigma @ 20mm f/2</TD>
</TR>


<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2953.JPG">
<br>Canon @ 20mm f/2.8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2960.JPG">
<br>Sigma @ 20mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2954.JPG">
<br>Canon @ 20mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2961.JPG">
<br>Sigma @ 20mm f/4</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2955.JPG">
<br>Canon @ 20mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2962.JPG">
<br>Sigma @ 20mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2956.JPG">
<br>Canon @ 20mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2963.JPG">
<br>Sigma @ 20mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2957.JPG">
<br>Canon @ 20mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2964.JPG">
<br>Sigma @ 20mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2958.JPG">
<br>Canon @ 20mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/20center/HP8F2965.JPG">
<br>Sigma @ 20mm f/16</TD>
</TR>

</table><br><br><hr>

































Here are some comparison shots using a 1Dmk2 with 1.3x crop factor.  <hr><br><Br>

<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 35mm Corner Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 35mm</td>
<TD>Tamron 28-75mm f/2.8 @ 35mm</TD>
</TR>



<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2978.JPG">
<br>Canon @ 35mm f/2.8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2984.JPG">
<br>Tamron @ 35mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2979.JPG">
<br>Canon @ 35mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2985.JPG">
<br>Tamron @ 35mm f/4</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2980.JPG">
<br>Canon @ 35mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2986.JPG">
<br>Tamron @ 35mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2981.JPG">
<br>Canon @ 35mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2987.JPG">
<br>Tamron @ 35mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2982.JPG">
<br>Canon @ 35mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2988.JPG">
<br>Tamron @ 35mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2983.JPG">
<br>Canon @ 35mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35corner/HP8F2989.JPG">
<br>Tamron @ 35mm f/16</TD>
</TR>

</table><br><br><hr>


<TABLE WIDTH="90%"  CELLSPACING="1" CELLPADDING="4" BORDER="1">
<h1>Lens test @ 35mm Center Crops</h1> 
<TR>
<TD>Canon 16-35mm f/2.8L @ 35mm</td>
<TD>Tamron 28-75mm f/2.8 @ 35mm</TD>
</TR>



<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2978.JPG">
<br>Canon @ 35mm f/2.8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2984.JPG">
<br>Tamron @ 35mm f/2.8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2979.JPG">
<br>Canon @ 35mm f/4 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2985.JPG">
<br>Tamron @ 35mm f/4</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2980.JPG">
<br>Canon @ 35mm f/5.6 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2986.JPG">
<br>Tamron @ 35mm f/5.6</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2981.JPG">
<br>Canon @ 35mm f/8 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2987.JPG">
<br>Tamron @ 35mm f/8</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2982.JPG">
<br>Canon @ 35mm f/11 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2988.JPG">
<br>Tamron @ 35mm f/11</TD>
</TR>

<TR>
<TD><img src =  "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2983.JPG">
<br>Canon @ 35mm f/16 </TD>
<TD><img src = "http://www.etischer.com/1dmk2/lenstests/Canon_16-35mm/35center/HP8F2989.JPG">
<br>Tamron @ 35mm f/16</TD>
</TR>

</table><br><br><hr>