To TC or not to TC? That is the question.

[Shortsighted]

 While my present Canon 300mm f4 L-lens does not have the AF speed and resolving power of the fabulous 300mm f2.8 L-version, some preliminary research that I’ve conducted suggested that my plan to couple it with a Canon 1.4x Mk III teleconveter would result in a union worth pursuing. The converter would reduce the amount of light reaching the AF mechanism by half, the equivalent of one f-stop, thereby effectively resulting in slowing my lens to f5.6, representing the limit needed for a functioning autofocus on my old DSLR.
 
 
 Of course, if I manage to replace my camera with a Canon R-series design then AF will continue to be available past f16. I know, it boggles the mind. So that using a Canon TC on a Canon lens coupled to a Canon mirrorless camera should be an assurance of a successful collaboration. This conclusion might not be as dependable if I were to introduce third-party products.
 
 
 The mighty 300mm f2.8 L-lens is so stellar in its performance that it can even handle a 2x TC and still deliver good AF action and produce sharp images to boot. An attached TC just magnifies the limitations of a lens and the sublime f2.8 is perfect enough to withstand the scrutiny. I say Watson, there is a reason it costs an arm and a leg, whot!
 
 
 If a new camera is introduced into the equation then the resultant compounding of IBIS (In-Body-Image-Stabilization) with native lens ‘IS’ might even occasionally make a 2x TC successful with my more modest lens, especially since the extra power requires less cropping (300mm vs 600mm) and therefore with less cropping the sharpening tools deployed in post-processing are working cleaner. The two f-stops of light attenuation on my lens, reducing it to f8, would still autofocus favourably when coupled to a Canon R-series camera body, although not so if coupled to my present DSLR.
 
 
 A Canon TC generally runs in the neighbourhood of $500. and that is substantially less cost than purchasing a longer lens, which would run into several thousands of dollars, which is several thousand more than I have to work with.
 
 
 A further benefit is that a TC does not alter the parent lens’s minimum focus. For my lens that distance is 1.5 meters. With a 1.4x TC attached it transforms into a 420mm f5.6 lens  but retains its 1.5 meter minimum focus, which is shorter than any genuine 400mm lens can manage.
 
 
 Both the 100-400mm f5.6 L IS II Canon zoom and my older lens share the same size objective lens, about 75mm (3”) and therefore have comparable resolving power. The newer zoom has second-generation image stabilization compared to my lens’s first-generation, but when coupled to a camera body with IBIS it becomes a mute point. The newer zoom lens has more coatings but also carries more glass elements, making it heavier and harder to wield in the field. The 100mm–400mm zoom lens is weather-sealed better than my older lens, so I will have to be sure not to place it under the weather. I can live with that.   
 
 
 I guess what I’m saying is that I’m now ready for the onslaught of advise and censure that comes with my present course of reasoning, as posted, to acquire a TC for my telephoto lens. Everyone’s a critic, so bring it on because I can take it. Show me the error of my disillusionment. Actually, I’m now a little worried because my batting average sucks.
 
 

[lovemypt]

I have used converters for many years, mostly with limited success, really depends if you are looking to get that id shot ...  or  up close detailed shot, like that of comparable prime lens in same focal length range , which they will not

converters will not work / or work well if the combined f stop exceeds over 5.6   with both DSLR's and R camera, although I read Canon Mark 4 IV can , but haven't had one to try
I started off using sigma 300mm 2.8 on a sony with both  1.5  and a 2x. I found the 1.5 was never used as I preferred reach of 2x  more.   The 1.5 worked perfectly and no notice to speed or quality was noticed in pictures , while 2x  worked  but a reduction in speed was noticed and pictures were never as sharp as I wanted, could of been cause by using sigma with sony combo instead of sony to sony to sony. The 300m was great but just not enough reach for what I shoot

I used now  a Canon 7D2  with 400mm  F4,  with option of 1.4 x  for increased distance.  I find the converter has no effect on operation of camera and speed and quality are not effected at all, but reach is still enough in most situations.   I borrowed a 2x from  a fellow birder and tried for a it, but found the speed was cut down dramatically.  It was taking 5-10 seconds for focus to come in and won't work for the warblers I was chasing.  For distance and still images might be fine but not moving subject,  the 2x would put F-stop up to 8  over the 5.6 threshold

I bought a new R6  a couple of years ago and still getting used to it.  In general, 1.5 works well on R6  but not as good as my older 7D2, I can see a quality difference between....... with and without converter   which I don't see with 7D.   I am not 100% convinced the newer R cameras are better then  DSLR's.  Yes, there are alot of new features and options with new camera's  but I personally don't see the increase in quality of pictures,   my 7D will stay in equipment lineup

As I find I use the converter for distance only, I have gone with another approach now.... I bought a Nikon P1000   with a huge zoom  ( up to 2000mm)  and use this for my distance shots now.   Yes, the quality of shots is not the same as a Prime lens and body,   but the reach is incredible  and considering the distance I am shooting over, I find these shots quite acceptable.
If quality of pictures is your end goal, probably better to wait for a used Prime lens to become available,   converters are expensive and have no resale valve.............  If anyone has an older Sony and wants , I have a 1.5 & 2x  converter I would pass on a reasonable price
another option.... Vistec has rental department, could rent one for weekend and try out to see if it suit your needs before buying

[Shortsighted]

 Thank you for your reply and opinion because they are much appreciated. Obviously, I’ve never tried a Canon R-series body to see if its performance is anything approaching the hype. As you suggested, I could rent one from Vistek, except that I can’t get all the way over there from my present situation and can’t spend $250.00 for an experiment. Nonetheless, I was unaware that this camera R-body fails to AF well at equivalent lens speeds exceeding f5.6. My online research would indicate otherwise, but you have used an R-6 so you should know. The Canon lenses available to date for the R-series bodies are by no means of L-lens quality, which you pointed out once before on this forum, perhaps better placed in the realm of kit lens. They have slow speeds, such as the 600mm f11 and yet they autofocus. By all reason therefore, a legacy lens coupled to an R-body with the adapter in place should do the same, with or without TC in series, n’est pas?
 
 
 My consideration of replacing my old Dx-DSLR with a Canon R-7 was not solely based upon being able to AF past f5.6 because I know that the Canon 7D MkII can handle f8, it’s just that the R-body camera has IBIS and that might make a huge difference beyond the first generation IS on-board my old 300mm f4 lens. My 70 – 200mm has no IS at all! The 7D does not have the IBIS feature. I would love to use a 300mm f2.8 lens, or something like your 400mm f4, but these items of kit are just way too expensive unless their use generates some level of income. Even a used lens of this kind is over five grande! Older versions with “IS” or w/o IS are not even available anymore. They were all bought out when IBIS was first introduced because the lack of top-notch stabilization was then no longer considered a problem for owning an older lens.
 
 
 Of course, there is a simple solution to all this. Just give up any hopes of ever getting back out in the field and let yet another hobby fall off the cliff due to lack of funds. I think that I will purchase the Canon 1.4x TC Mk III anyway. I can have something to look forward to and get some TC experience. Just wait, as soon as I get the TC the camera will crap-out for good. It’s a corollary of Murphy’s Law.


BTW, I'm pleased that you are still on this forum and have not entirely moved on to greener pastures. Oh, wait, that didn't come out quite right. I didn't mean to imply you are out-to-pasture. Having a 7D II and a 400mm f4 is a terrific incentive to postpone the pasteurization for some time, I hope.

 
 

[Shortsighted]

Well, I've chosen to TC and at least taste this leprous distilment. As expected, the Canon 1.4x TC Mk III is a well-constructed piece of kit. The effective extension of my focal length takes some getting used to,.  having spent my few years birding with only 200mm. The resultant boost on my 300mm lens bring it to 420mm f5.6. The narrower field of view makes targeting more difficult and the AF is easily distracted by objects in front of and behind my subject. I tried it out this morning for the first time.
 
Blue jay in nest


It's a two bird job


FOY chipmunk


These blue flowers are abundant



Thirsty blackbird

[TransAtlanticGoose]

The extra magnification seems to be paying off.
That chipmunk can't believe how closely you are watching him.

[Shortsighted]

Yes, I'm glad that I have the TC but I wouldn't use it for warblers because the AF is not fast enough to follow frenetic birds. The Great Blue Heron that I encountered the other day was so close that the TC's effective 420mm focal length would have secured only its head in the frame. The presence of tall grass and reeds would have made AF tricky. I could have shut off the AF and focused manually but I have a black sock over the lens and trying to peel it back while under the camo net and also keeping still so as not to spook the heron was not worth it.