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Teleconverters: Quantaray 2x vs. Sigma 2x

Hi there,
I have been thinking about getting the Quantaray 2x TeleConverter for my D-SLR and mostly Sigma lenses. I came across an article from your website and am wondering: What do you think about this TC? It is in my budget and do you think it is worth getting? I have heard it doesn't AF well, so would I mostly have to manual focus? Please advise, and I am thinking about getting it but want your opinion, thanks very much!

Jojo Ma
Tue Jul 6 16:07:02 PDT 2004

"What do you think about this TC?"

This teleconverter is ok. It is quite sturdy and robust. However, I think it only has 4 elements, instead of 7 elements, which is why it is quite affordable.

It is probably the same OEM as the Kenko 4 element teleconverter.

"It is in my budget and do you think it is worth getting?"

It is better than not having a teleconverter at all. See my "Stacking Teleconverter" article.

If you can afford a teleconverter specifically designed for your lens, then you should get that one. See my "Sigma teleconverter compatibility" article.

"I have heard it doesn't AF well, so would I mostly have to manual focus?"

It depends on the camera/lens you use it with. All teleconverters have this potential problem.

The issue is in the light-loss when you use teleconverters. (The "Stacking Teleconverters" article will show you how to calculate light-loss.) Most SLR cameras have a minimum light for AF at f/5.6.

If your lens has a f/5.6 aperture, then your camera will be unable to AF with the light-loss from the teleconverter. In this case, MF is your friend.

On the other hand, if you are using the 2x teleconverter with your f/2.8 lens, then you would effectively have a f/5.6 system, which your camera can still AF (perhaps a little slower).

Chieh Cheng
Tue Jul 6 16:17:59 PDT 2004

chieh, thanks for the prompt reply. here is what ritz camera (who sells the quantaray TC) says about the 2x TC:


  • 2.0 APO Specifications:
  • Magnification: 2.0 times
  • Lens construction: 6 elements in 5 groups
  • Dimensions: H 2.6" x L 1.78"

it SEEMS like good specs, similar to the Sigma 2x. APO glass, 6 elements, etc. I think I will give it a shot at $80. I will be trying it on my Sigma 70-200 f/2.8 also, so we'll see how it works.

lastly, what does sigma mean that using their 2x TC you can damage certain lenses? they make it seem like there is something dangerous about using lenses other than what they list on their compatibility chart? is it okay to use the Quantaray 2x TC on ANY EOS or Sigma lens?

Jojo Ma
Wed Jul 7 09:19:56 PDT 2004

Sound like they improved this teleconverter. Could even be the same one as the Sigma one. Sigma has made a majority of Quantaray lenses before.

"what does sigma mean that using their 2x TC you can damage certain lenses? they make it seem like there is something dangerous about using lenses other than what they list on their compatibility chart?"

It is a statement to cover their backs. A few years ago, maybe still today, Canon had a 1.4x and a 2.0x teleconverters for EOS camera and EF lenses. These two teleconverters are very well corrected and are very good. However, in order to make them that good, the correction required lens elements that pertude from the ends of the teleconverters. Therefore, only worked with certain telephoto lenses. On other lenses, they will make contact.

"is it okay to use the Quantaray 2x TC on ANY EOS or Sigma lens?"

I don't know if anyone can answer that question. I have not seen the physical characteristics of this new teleconverter. If it is like mine, with no pertuding elements, there is a very good chance that it will work on most lenses and cameras.

But there could be lenses other there that have pertuding elements that could interfere with this teleconverter.

Chieh Cheng
Wed Jul 7 09:34:18 PDT 2004

I took a closer look at the spec of both teleconverters. And they do indeed look the same!

Sigma 2.0X Teleconverter EX APO technical info:


  • Mount: Canon EF (AutoFocus)
  • Lens Constructions: 5 Groups 6 Elements
  • Dimensions (Dia x Length) 68 x 45.3mm / 2.6 x 1.78in
  • Weight: 234g / 8.3oz

I think you found a good deal!

Chieh Cheng
Wed Jul 7 11:17:10 PDT 2004

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Title: glass in Quantaray 2X AF Teleconverter
Weblog: Camera Hacker
Excerpt: I came to this site to find what others thought of Quantaray 2X AF Teleconverter, and this [page] gave me that info. Thank you. One big question though, I've been told that the glass in this teleconverter was junk, what do you think of it?
Tracked: Wed, 10 Jan 2007 13:12:18 -0800

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