Why Tamron 17-50mm Not canon? not VC and etc

This is the very first test image from my Tamron 17-50mm taken at F/5.0,30 sec shutter speed.

This image is straight out from camera without any post processing. The image quality is sharp and better compare to Tamron 18-280mm. As usual many will be comparing to sigma and canon image quality. 

You can read about the Tamron 17-50mm Review here. http://www.photozone.de/canon-eos/289-tamron-af-17-50mm-f28-sp-xr-di-ii-ld-aspherical-if-canon-test-report--review?start=1

For canon, http://www.photozone.de/canon-eos/178-canon-ef-s-17-55mm-f28-usm-is-test-report--review?start=1

and of course sigma, http://www.photozone.de/canon-eos/531-sigma1750f28os?start=1

For image quality, canon wins overall. But the price of canon is about RM 3400++ in Malaysia. Which you can afford 2 Tamron lens or 2 sigma lens. But of course we cannot compromise the image quality as I have done before. Thus I compare Tamron and sigma lens together. Of course Tamron image quality comes quite close to Canon, I have also read some review that the Tamron lens has sharper image than nikon lens. I am not sure how true this can be. But nonethless If you look at the sample image and also lab MTF chart, everything looks quite constant from F/2.8 to F/11 throughout the zoom range. this is the lens that will give you decent overall image quality. Though the lens has some curvature problem yet it is a very good bargain lens. So again corner is a problem, we will test it out until we put it into daily life usage.

Why not sigma? No doubt sigma has excellent center image quality even at wide open, at the test chart it even beats canon, but overall it still lose to canon and tamron because the edge and border is just too soft wide open. Even stopping down sometimes the soft border might just a problem for landscape and some wide angle photography (which I think so). But if you take a lot of portrait and the subject always position at the center, I think Sigma lens should be one of the choice because Sigma takes the sharpest image at center.

For pricing wise, Canon is about RM 3400++, Sigma RM 2300++ and lowest is Tamron at RM 1200+-(non VC Version) with VC is about RM 1600+-

The reason why pricing has become a criteria in lens selection is because both these 3 lens are cropped sensor lens, it is not usable later when I am going for full frame camera in few years to come. More or less if you buy a Canon lens you might actually able to get another ultra wide 6-18mm Sigma or Sigma 50mm F/1.4 which will take better picture and you will still have a 17-50mm F/2.8 zoom lens? In order to save money for later, I have decided to go fo Tamron 17-50mm non VC version. But why non VC?

For the VC part I guess it is just experience. I find that my previous Tamron 18-270mm VC has given my some problem due to VC while taking bracketed exposure or continuous burst shooting. I have the camera on tripod or steady ground, but out of 10 pictures I took there will be one picture that is blur inclusive the background. it seems like some kind of motion blur. But the camera is position on tripod and shotting at 18mm. Even with handheld it should have those kind of motion blur. It is very obvious if you put your camera at the same place and trying to shoot more than 9 exposures with high speed burst. Of course VC is good if you are shooting in dark. But maximum of 50mm will not need much image stabilization even using handheld. So far 1/15 shutter speed has given me decent image quality.