From what I'm told, you and I both already have a built-in teleconverter of sorts. The 60D (I have a 70D) has what is called a cropped sensor. Because it's a smaller sensor, it appears to have the same effect of a 1.5x teleconverter. The pixels are compressed so the image quality isn't as awesome as a full sensor like a 6D or 7D. I've gone into a few camera shops asking about teleconverters and I've been counseled against it every time over the last decade. With a 400mm focal point, my lens, in effect acts like a 600mm.
It appears that both of the following sites assume you are using either a cropped sensor camera OR a full sensor with extendor...

link:https://petapixel.com/2016/11/14/teleconverter-vs-crop-sensor-teleconverter-bad-decision/

and: https://www.diyphotography.net/shooting-wildlife-crop-sensor-vs-full-frame-1-4x-teleconverter/

Sounds like improve everywhere has struck again.

see the story and video: https://improveverywhere.com/2006/04/23/best-buy/

You might be interested in this topic in the main photography area - "Sigma 100-400mm vs Tamron 100-400mm vs Canon EF 100-400mm".
I was going to purchase a 100-400 mm lens. I had originally thought I'd get a used Canon lens for my EOS 70D. Then was directed to the Sigma lens. After researching Canon, Sigma, and Tamron; I asked about them in the above topic. Take a look at the link for how the Canon lens was made at lensrental.com. I'd imagine that there is something similar for the Nikon lenses.

Link: http://www.uglyhedgehog.com/t-512554-1.html

at the Ridgefield National Wildlife Sanctuary

geometric views of creation.

I had been hoping to purchase a used Canon, but last Saturday was directed to Sigma by a photo shop clerk. I wanted some more opinions about Sigma and Tamron quality and it would appear from research online and here that they are probably pretty good. However, as someone said in this forum that I'd probably always be looking back and wishing I'd have gotten the Canon. A post with a link to lensrentals.com shows how they break down the insides of the Canon. It's pretty darned impressive how well built it is.

No one has mentioned using their lenses in weather and I had thought I read that the Canon was sealed well, but the Sigma and Tamron weren't so wonderful on that front. I could be remembering incorrectly.

To your point, my wife saw some Canon refurbished lenses a day or so online and is urging me to spend the extra bucks if I want to. I have some refurbished electronics and am usually satisfied. It's good to know that you have a good history with Canon's refurbs.

Thanks to all who gave their opinions and experiences on the lenses. I've enjoyed learning from you. I hope to learn more.




Raspberries to the two who trolled.

Holy cats. What a great article. I loved some of the following lines from the article by Roger Cicala:

"I usually laugh when people describe a lens as “built like a tank” ...the lens they are describing has a thick, heavy outer metal shell filled with tiny delicate pieces that break and wear out with great frequency. But this lens is built like a tank inside and out."

"I’ll point out those a... double the size of the screws we usually see assigned to this kind of task."

"Removing the board gives access to eight large screws (four to six is what we would have expected) holding the rear barrel in place."

"look at the lower helicoids – there are six channels, of which two are visible .... Most lenses have three channels and collars. That’s a huge amount of increased stability when the barrel extends away from the lens."

Wow!

I'm not sure why you feel it's ok to attack my question, but your responses above dismissing my questions give me a good clue as to how valuable your input is. Thanks for the head's up.

My original question was really which one is better, Sigma or Tamron? If the canon is twice as good, I'd like to know why. If you are commenting on futility, tell me what I missed above in the comment "Canon all the way"? I can certainly appreciate brand loyalty, but I'm not sure my pocketbook can handle twice the cost? If I'd be happy with a used one which is available, please share the qualities that would make it a better purchase than the two that I can afford.

So I see a greater fan base for the canon lenses, but I don't have the budget for a new one.
I appreciate the comments, but I'm not sure why I should go with a Canon (I'd have to purchase a used one on my budget.)
Could you please comment on the qualities of each lens for comparison's sake?

I'm trying to determine which lens to purchase. The Sigma 100-400mm f/5-6.3 DG OS HSM or the Tamron 18-400mm F/3.5-6.3 DI-II VC HLD All-In-One Zoom For Canon (or for over double the price, the Canon EF 100-400mm f/4.5-5.6L IS II USM Lens).
In reading reviews, it would appear that they both have pro's and con's. The Sigma seems to lose points for speed of auto-focus, but I'm finding I use that less and less. I use the auto- to focus, then switch to manual to fine tune.

If you have a Tamron or Sigma, I'd like to hear your opinion.
Thanks.

( It was by webmaster's request that I make this a new topic even though I posted it in a different post earlier today. )

I'm trying to determine which lens to purchase. The Sigma 100-400mm f/5-6.3 DG OS HSM or the Tamron 18-400mm F/3.5-6.3 DI-II VC HLD All-In-One Zoom For Canon (or for over double the price, the Canon EF 100-400mm f/4.5-5.6L IS II USM Lens).
In reading reviews, it would appear that they both have pro's and con's. The Sigma seems to lose points for speed of auto-focus, but I'm finding I use that less and less. I use the auto- to focus, then switch to manual to fine tune.

If you have a Tamron or Sigma, I'd like to hear your opinion.
Thanks.