A few observations:

Technipix is using QuickTime for a player vs. flash 9 which I think at this time is still a better viewer. 

Stay away from auto focus and use manual.

Try a lower ISO with a longer shutter speed.

Also, Technipix is going fullscreen so he may be producing a larger image and file size than you are which will result in a better image.

Good Luck...
TTurner

Muphian446,

What are your VT dimensions and file size?  Are you also sharpening the image before you publish? One more - what size are the original photos and are you shooting Raw? Well that was two.

TTurner

Short answer Sigma 8 f3.5  best aperature is f/8

Long answer:  Set your tripod /camera and Sigma 8 about 1 meter or 3 feet in front of a texture wall.  I used a brick wall.  With the camera set in Aperature priority  fix the f-stop value to read 3.5 and let the camera determine the shutter speed.   Suggest not shooting raw for this test

Take 1 picture at each of these f/stops

f/3.5
f/4.0
f/5.6
f/8
f/11
f/16

Now open all 6 images in your favorite photo editor.  Set all 6 images to view at 100%.   Now compare the sharpness.  We found f/8 and f/11 to be the sharpest.. and decided on f/8.

Final thought,

An alignment problem between exposures could be causing the final product to be soft.  Shooting RAW and getting your exposure differences from that process will ensure that all of the images line up correctly.  I here Smooth is the man for learning this skill.  Also, the contrast range did not seem that high in you demo, so maybe do not use HDR at all for this job.  If you have Photoshop you can use Shadow/Highlight to help dig out underexposed areas without HDR.  There are many talented folks on this forum (more talent than me) that might like to play with your images.  Could you post a set of photos and maybe someone could help you with a better result after seeing the originals. 

Take care...
TTurner

Oh, forgot some additional information. 

When using Sigma 8mm at f/8, rotate the ring to the INFINITY MARK oxo [tape it place so the ring will not move].  Then depth of field where ALL will be in focus is 4" (10cm) in front of the lens glass to infinity . 

That is why it is necessary to switch the 'auto focus' OFF because it is not needed.  

Keeping the auto focus switch in the on position will cause each of the 4 or more images to try to alternately focus on near and far objects.