After a week long wait (rain) finally (Sun &) Moon in Memphis. Not strictly comparable since I used the TC-2001 on Sigma (150-600s) in addition to D810 crop mode & the HDR processing – that too six months apart. Still…
Detailed files @ Moonshine in Memphis - Tiger Rider
D810(1.5Crop) -Sigma @1800mm on 2014-12-09 (Sigma600x TC-2001)

D800E-Tamron @600mm on 2014-06-12

I do have mixed feelings comparing with Tamron (it was an amazingly great lens (especially for its price) and with 99% success rate (I mostly used in perfect light conditions – hence may not be able to strictly compare it)).
Here is some of my unscientific quick observation based on the Zoo test on another mostly cloudy day (
• Futuristic custom setup and firmware update is an amazing feature of the Sigma. BUT Some strange reasons my custom setup C1(C1: AF-Focus accuracy priority, Focus Limiter- 8.53 to 100 feet, OS- Moderate view mode) & C2(C2: AF-Focus accuracy priority, Focus Limiter- 100 to infinity feet, OS- Moderate view mode) did not focus (only tested at zoo)
• TC-1401 is another key reason for switching from Tamron to Nikon. In contrasty and good lighting situations it mostly worked fine (file Name DSC_6376 (1155) to DSC_6582(1361)) - Surprisingly while shooting the well lit moon (12/08/14) even ViewFinder AF worked on TC-2001. But I had trouble in ViewFinder focusing especially in less contrasty situations (for example DSC_6582(1362) to DSC_6619(1398)). Even without the TC-1401 also the focusing was not great in such conditions (example especially the moon shots from DSC_5223 (2) to DSC_5227 (6)).
• Optical Stabilization is also terrific for Sigma especially on D810 – even on 1/125th (mostly shot faster than 1/500th) I got sharp images @ 600mm. Tamron was also not bad – if I remember, I even used to take it 1/200th @ 600MM.
• This is a monster piece of amazing looking & well-built glass. But motor was making noise when it is hunting for the focus - I can understand since it need to move one more extra-pound of glass comparing with Tamron and I don’t mind the noise as long it don’t break the motor
• This lens comes with big case & hood (wish I can get a less bulky lens cap also). With this lens, I forced to upgrade my bag from Bumblebee-220 PL to “Pro-V-610”. I took the baby stroller with me to carry the lens & bag – I may also suggest a monopod (it is not easy for me to carry around especially shooting whole day – especially for airshow where you need to shoot from all angles(Tamron was perfect considering its weight)).
• Sigma’s 4 year warranty is not bad – hope they will match it to 6 year warranty of Tamron (my recent experience with 24-70 Tamron service was stupendous (<3 day))
Again this is an amazing piece of lens and also we need to considering it from the futuristic perspective too (hopefully Sigma will update the firmware (as they did with Cannon) and take it to next levels in coming days).