Teleconverter

[wdh777]

I'm considering getting a 2.0 teleconverter for my 70-200 2.8. Other than going to 5.6 does it also reduce the iq?   Thanks I'm still learning here.

[viggen61]

Absolutely. You can, however, make informed decisions about how much IQ you lose. In general, getting a Canon extender is better than a third-party extender, and the newer the Canon extender, the better.

[neuroanatomist]

It will reduce IQ.  Depending on which 70-200/2.8, the effect varies.  The original 70-200/2.8 IS takes a big hit, the non-IS takes a moderately big hit, the 70-200 IS II a small hit.  IMO, only the 70-200 II gives decent IQ with the 2x.

[mezzoutopia]

I just bought a Canon EF2Xmk3 Teleconverter last week and have tried it on my 300F4L and 70-200 2.8Mk2 lens.  The EF2Xmk3 converter does reduce the image quality of these 2 lens more so than compared to the 1.4Xmk2 which I have also.  If you do not need the additional reach, the 1.4Xmk2 or mk3 will be better.

[RGF]

Any piece of glass, not intergal to the lens, will reduce IQ.  If it improved IQ, then it would be part of the lens

[Mt Spokane Photography]

Even air reduces the IQ, the further away you are, the more are between you and the subject, and the IQ is lowered.

Now imagine 7 elements of glass as in a TC.  There is a definite loss of IQ, and the TC is also a magnifier, so the faults that exist in a lens are magnified.


This  does not mean a TC is bad, the end result might be better than cropping, but that depends on the lens, TC, and camera body.

[greger]

I'm using both the 1.4 and 2X Teleconverter with a 70-200 F4 IS USM Lens. The 1.4 works fine and I have gotten some really nice BIF pics with this combo. Using the 2X is harder for me and I am still trying to get the results I would like.
With my 40D the pics were fuzzy handheld. With the 7D they're a little better. As it's early in the year, I might get better results when the weather gets better. I would like to shoot with the sun and me in the West looking back at the Eagle.
This is handheld shooting from the North which is better than shooting from the south. The 2X makes my lens an F8 Manual Focus.The 2.8 would become a F5.6 auto focus lens. I have seen good results on the web. You may or not get results that make you happy.

[AlanF]

Any piece of glass, not intergal to the lens, will reduce IQ.  If it improved IQ, then it would be part of the lens

This and the other dogmatic replies and all those who have answered yes that IQ is always lowered by by a TC have answered a very badly phrased question and are only half right and are also half wrong.  If you compare the IQ of the native lens at half the distance from the subject as the lens +2xTC, then the native lens will give better IQ since the image has the same size in both cases.  But, if you compare the IQ when both native lens and the 2xTC combo at the same distance, then a good lens with a good TC will give better IQ than the native lens rezzed up. Look at comparisons on the The-digital-Picture site, for example. Of course, a bad combination could give worse results.

[simonbratt99]

I have the 70-200L IS II with the 2x canon and its great for video (on 5d mk2)
Heres one i took last year
http://footage.shutterstock.com/clip-2260261-stock-footage-young-deer-walking-in-spring-bluebells.html

[OCwildlife]

Some hesitation on BIFs, could be frustration on the focus for you. No comparison on that part. The extra glass is usable, but not for everything. I would say using auto ISO is a good idea to insure enough shutterspeed for moving birds. Posed birds take pretty well with the new 2x. I am happy with it on my 500mmf4IS II. I won't use it, for instance if the shoot is important like one of a kind birds like Golden Eagles, etc. Your keeper rate goes down.

But in good light and with good shutterspeed control  and posing targets you may have some fun with it. Your DOF will be smaller area of the target also. I use mine occasionally. The newer model is the only way to do it right. What camera do you have?

[skitron]

I have the 70-200 IS2 and the 1.4 TC3 and very pleased with that combo. But that keeps me at f/4 wide open so still useable in less than ideal light. IQ hit is barely even perceptable. I realize you are asking about the 2x but chimed in anyway in case you decide to consider going "shorter".

[Mt Spokane Photography]

Any piece of glass, not intergal to the lens, will reduce IQ.  If it improved IQ, then it would be part of the lens

This and the other dogmatic replies and all those who have answered yes that IQ is always lowered by by a TC have answered a very badly phrased question and are only half right and are also half wrong.  If you compare the IQ of the native lens at half the distance from the subject as the lens +2xTC, then the native lens will give better IQ since the image has the same size in both cases.  But, if you compare the IQ when both native lens and the 2xTC combo at the same distance, then a good lens with a good TC will give better IQ than the native lens rezzed up. Look at comparisons on the The-digital-Picture site, for example. Of course, a bad combination could give worse results.

Since he mentioned a specific lens, the 70-200mm f/2.8, which does not take TC's particularly well, our answers seem to be fine.
 
Many of us have extensively tested TC's with our lenses as well as viewed TDP.
 
Here is a crop from TDP of the 70-200mm f/2.8L and no TC

 
Now, with the Canon 2X TC III
 

 
Its pretty obvious what the best TC does to the images from the lens indicated by the OP.

[AlanF]

The TDP iso chart tests are just what we want for comparing the 70-200 mm with a 2xTC at 400 mm with say the 100-400 mm at 400 mm.  But, the pair you show compares the 70-200 mm with the 2xTC at twice the distance from the chart as the same lens without the TC. What we also want to know is it worth using a TC compared with the native lens. To answer this, elsewhere in the TDP site he compares the same lens at the same distance from a target (a flower) with the lens plus 1.4xTC and 2xTC. In each case, the image without the TC is rezzed up to the same pixels as with the TCs, and the TCs give better images.

I have done the same tests with my 3 TCs and a variety of lens.  For the 300 mm series II with the series III TCs, the combos are better than the rezzed up native lens, just as on the TDP site. So, I use the TCs whenever necessary. But, for the 100-400 mm, the addition of a 1.4 TC is no better than rezzing up the native 1.4x. So, I leave the TC at home for that lens.

Now do you see what I am getting at.

[yablonsky]

I used the Canon 1.4 II and the Kenko DGX MC4 1.4x with my 300 4L IS and my 70-200 4L IS.
The result is pretty much the same. Contrast ist missing. Images get hazy.
I also tried a KENKO MC7 DGX 2.0x once, but this was not acceptable.
Finally 1.4x does not give enough magnification and 2.0x creates unacceptable results.
So I stopped using TCs and started using crops from the original images.

[AlanF]

Here are the links to the TDP TC reviews with the great Canon primes;
http://www.the-digital-picture.com/Reviews/Canon-Extender-EF-1.4x-III-Review.aspx

So, if you are stuck at 100 m from a bird or a flower, then you will get better IQ by adding a TC to the high quality lens. So, in this case the TC increases IQ.

If, on the other hand you can stand anywhere you want, you will get better IQ by moving closer and removing the TC. In this case, the TC lowers the IQ of the same lens.

For Yablonsky's two zooms and for my 100-400 mm L, the IQ is decreased to the extent it is lowered at all distances.