Reach
Price
Build

Loss of contrast
Doesn't transmit effective F-Stop
Loss of sharpness

Can't be beat for the price PROVIDED you have an excellent lens to begin with. I shoot with a Canon 20D and have used this converter successfully with my Canon 70-200 F2.8 IS zoom (excellent lens to begin with). It won't transmit the corrected f-stop value to the camera (no biggie). I shoot raw images and adjust later (highly recommended).

I've found my best results are to underexpose by 2/3 to 1 stop. Also, the teleconverter makes for a noticeable loss in contrast, so this will need to be adjusted as well. It's a good idea to stop down the lens (experiment), likely 2-3 stops for best sharpness. I have actaully had good results at F4-F5.6 (1-2 stops indicated) effective F8-F11. Do understand that you will lose some sharpness, some of which can be compensated for with selected use of USM in Photoshop or similar program.

Probably a good idea to use a monopod if availalble. I haven't used one since my image-stabilized lens already gives me 2-3 stops. If you don't have an excellent lens to begin with, don't bother with any 2x converter. Go with a 1.4x or none.

Geat for when you need that extra reach. Can't comment on how well it works for full-frame camera.

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Inexpensive (I refuse to say cheap - it's solidly built)
Perfect for non-professionals.
DOUBLE YOUR REACH!

Normal loss of 2 stops of light.
Loss of AF (to be expected with slow focus lenses anyway) at extreme zoom.

Can't afford a 600mm lens? Like to shoot nature photography at your local park?

If you're like me and already have a 300mm lens in your bag, and you don't have the money to burn on an expensive lens for taking nature photographs for your own use, I would recommend this lens to you, because for the price you pay, you'll extend your reach and you'll be able to grab shots you can't get now.

However, at the same time, don't expect to be shooting the same way you shoot with your lens now when you add this extender to your camera.

Shooting with a 600mm lens at f/8 (Your f/5.6 ratchets up 2 stops) is going to be hard. You're going to have more camera shake because of the amplification of every vibration due to the distance. You're going to need at least a monopod to minize that.

Then, you're going to lose 2 stops of exposure and without bright light, you may find exposure times too quick for you to take a clear picture at reasonable film speeds. Shooting at ISO 200 on a lightly cloudy day had me at 1/400 for a white bird 50-100ft away.

You're also going to have to learn to manually focus instead of relying on AF for all but sports mode (where the servo mode may bail you out). Without a split screen, this is hard with a digital camera....but it's fun and makes you feel all the more a 'real' photographer....double up on how many shots you take, so you can take home the GOOD one - digital film is GREAT for this alone

But, for $80, you'll get in close, and you'll be happy with the results...see example at http://www.richgautier.com/img/bird_cropped.jpg. This shot was taken with a Tamron 70-300mm lens with the Quantaray 2x tele-converter. ONLY THE TOP LEFT WAS CROPPED off (so you can see the edge results bottom-right). The image was resized for the web, but I'll be happy to share the original file (1.76MB) with anyone who emails me.

Cheap, and not awful.

Minor chromatic aberration, and loss of contrast.

This teleconverter looks suspiciously like the low-end Tamron-F AF 2x converter. I've compared the two side by side, and the glass and housing look identical, except that one is stamped "Tamron" and the other "Quantaray", and the Tamron is a few millimeters longer. Quantaray is usually made by Sigma, but clearly something different happened here. Because the Tamron costs twice as much as the Quantaray, I can't see any reason why one would ever buy it. You should get the Quantaray if you're interested in a cheap non-awful 2x TC. Considering how cheap this TC is, I can't complain. I've used this with the Sigma 28-300 macro lens, which is a surprisingly good lens considering its low cost and wide zoom range. With this combination, I can get reasonably sharp photos at the combined 600mm length. This is much better than I expected considering how cheap both lenses are, and how expensive most 500-600mm zooms are. However, there are a few catches: 1. With my lens combo, there was slight chromatic aberration toward the edges. This was not present in the original lens. The CA was less than I expected for such a cheap item, but I would guess the higher end Sigma or Tamrons would not have any at all. 2. Pictures are slightly soft all over. If you want to show photos to anyone else without enbarrassment, you'll have to enhance both contrast and sharpness using software. 3. Like all TCs, you lose 2 stops of light. You'll need a tripod and you can give up trying to shoot anything that moves, like birds, wildlife, airplanes, etc. Unfortunately, that's most of what I wanted a long zoom lens for. Basically, this TC is a fun toy that will give OK results if you have a tripod and are willing to correct CA. But it makes your lens way too slow, so you won't be able to shoot anything that moves. I can only recommend it because it's so cheap.

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Tamron-F AF 2x converter, which appears to be IDENTICAL to this product but costs twice as much.

Very inexpensive. Good build quality for price. Works with lenses that don't normally work with a TC. Picture quality is very acceptable with my example.

Not the build & image quality of the Sigma EX and Canon TC's - Though not really a weakness considering the price!

After reading some of the negative reviews on the product, I felt I needed to put in my two cents worth… First of all, I bought this little gadget on a whim while walking through the mall with my wife and kids. A salesperson at Kit’s camera was showing it to a customer when I noticed that the front lens didn’t protrude out like the two Sigma’s I own (1.4x & 2x EX). So for the price, I thought it would be worth a try. Even though the unit is made by Sigma, it’s nowhere near the “Brick Outhouse” build of the Sigma EX series TC. It must be an earlier attempt by Sigma. Never the less, for the $80 I paid for it, it is built quite well. The really nice thing about it is the fact that its rear-set front lens allows the unit to work on every lens I have! It will only AF on fast primes and fast, fixed F-stop zooms. Manual focus is only tough on slow zooms like the Sigma 50-500mm at full zoom due to the low light making it to the view finder. The image quality is ten-fold what I was expecting from an $80 TC! In fact, I keep it in my pocket when on walkabouts and use it with my favorite walkabout lens (Canon EF 28-135mm IS). It will not replace my Sigma EX in my main bag, nor would I use it (nor any other TC) on a paid shoot, but it’s a fun little TC to play with on lenses that normally won’t work with a TC. Maybe I got a good example, but the loss of image quality is not bad at all – sharp as a tack corner-to-corner.

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Sigma 1.4x EX TC Sigma 2.0x EX TC Rented the Canons, but found they were not enough better to warrant the cost of upgrade.

Cheap Metal mounts will never wear out

Cheap Metal mounts will never wear out! AF barely works 2-stop loss in light volume Degrades image badly Not even as good as a low-quality consumer zoom.

"Other" means "everything but studio." The TC. What a piece of junk. Do yourself a favor and don't buy it. It has all the hallmarks of a low quality TC. Almost no AF in any lighting. It hunts for focus every time with my Elan 7N. When it does perform AF, it is slow and pretty much on a par with manual focus, except manual focus is faster and won't wear out your batteries hunting for focus. The images you make with this product will be crappy and you'll have a hard time getting them. I have been very unhappy with it. If you have to use 2 stops faster film, then you are getting 2 stops grainier images. And with the moderate to extreme degredation this TC will give you, why in the world would one ever buy it? Let me tell you again, in no uncertain terms, "DO NOT BUY THIS TELECONVERTER" Do not even inherit it. Save your money for a pro TC if you must have one, or get a prime/zoom of equal focal length. Mine came with a nice fake leather pouch and caps. It also came with a big blotch on the rear element, where the coating had been applied seemingly by hand. How embarassing for Quantaray. And me for wasting my money on such a hunk of junk. The only thing it has going for it is metal front and rear mounts. The rest of it is plastic. Hopefully it will get stolen or broken in the near future. I will not give it away or sell it, for humanitarian reasons.

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With good lighting, can work w/ AF. 2x magnification Inexpensive

Slows or renders AF ineffective under weaker lighting conditions. Requires camera stabilization- monopod, tripod, top of pickup cab or tailgate,... Photos often appear a little soft, loss of sharpness. Loss of light- about 2 stops.

For what it's worth, I seldom use mine. It's really not that bad of a piece of equipment, it's just that I've learned that I'd be better served with a longer zoom or perhaps a couple of longer primes. It's come to my attention that TCs were really designed for primes, not zooms. The AF cannot focus at times with it attached and focuses slowly when it does. The AF can and does work as long as there is good lighting. Elsewise, it really struggles to focus properly if it does. Not all is doom and gloom. If you mount your camera to a monopod, tripod, or otherwise stabilize your camera, you'll actually do at least okay. Handheld to a long range zoom- forget it. Hey, it's cheaper than a telezoom or primes. And a lot lighter to carry too. When mounting a TC, I'd suggest using a faster speed film than you'd normally use. Whether or not this is a weakness depends upon the user, as one will view it as such while another may not.

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snaps on quick

Poor image quality

Sharp image in center of picture with lots of distortion around edge

Inexpensive, nice quality.

Autofocus won't work with it attached.

An inexpensive way to increase your telephoto lens. There's a significant loss of light (1.5 to 2 stops), and autofocus won't work with it attached.

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