1.4 X extender for 150-600 C on my Canon 70D good idea?

Two thoughts:

1. I would not count on the extender working for anything other that the Sigma lenses.

2. The extender will likely push the max aperture out of AF range. If you don't mind going to a tripod and manual focus, this doesn't matter.

Great info, thanks. Do u think the extender will have better quality vs. cropping the image? Especially as its a 600 mm lens....

GuruNandan said:

Great info, thanks. Do u think the extender will have better quality vs. cropping the image? Especially as its a 600 mm lens....

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Given that you'll likely have to increase the ISO to maintain a reasonable shutter speed, possibly not. Aside from losing a stop & a half of light, it will not be as sharp even when focused properly.

Agree .... I guess i will drop the idea of buying the extender , arleast for the 150-600 lens....

Someone in another thread was suggesting that the 70D has f8 focusing ability, but I wasn't able to find anything that said that (in fact, I found something that said its max is f5.6). But if it does, 1.4 converters are not all bad when it comes to degradation... generally. The Canon 1.4 III is actually pretty good on most lenses. The thing you want to look out for when pairing a TC to a lens is the lens itself. My rule of thumb is, shy away from using them with lenses that don't work well wide open. Reports say TC's aren't ideal with the Sigma 150-600's, they don't say they are bad... just not good. My guess is because they need to be stopped down at the longer focal lengths for quality, I'd guess they are dangerously close to the diffraction limits and are very slow as far as light gathering.

GuruNandan said:

Do u think the extender will have better quality vs. cropping the image?

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I have tried a couple of TCs (Kenko and Canon) with good Canon lenses, and found that a 1.4x TC beats cropping to get the same image... _IF_ you can get accurate focus. I suspect that most of the "TCs degrade IQ" received wisdom comes from their effect on focus accuracy rather than their actaul effect on the quality of the final image with good focus (which is an improvement, in my experience).

The Sigmas are f/6.3 at 600mm, so you're already at a disadvantage for AF with cameras with f/5.6 AF. If you have a camera with f/8 AF (7D II, 80D), you're still at a disadvantage once you add the TC.

I would want to get some good feedback from users before I would buy the combination, or be sure that I am happy to use Live View AF.

GuruNandan said:

I am planning to buy the SIgma (Dont mind Tamron too, but i found the Soft locks , Focus limiter and Panning IS as added feature) 150-600MM lens to be used on my crop sensor Canon 70D. There is a deal for Sigma 1.4X extender for 50% off if buying along with lens. Now is adding an extender for this setup is worth it? or am i demanding too much of a zoom?

Is it worth investing the extender or just zooming the image and cropping should give me a close quality as adding an extender? I know the extender is cheap, but dont want to simply invest or fill my camera bag until its really worth it. I have my canon 18-135 STM lens, not sure if i can use the extender on that too.

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I dont think id bother...as the lens only has adequate to good IQ at 600mm it can only be worse ..have a look here but i cannot answer your question about extender vs cropping with this lens