70-200/4 IS USM PLUS 2X TC?

Discussion in 'Canon EOS' started by robert_thommes|1, Jun 26, 2011.

  1. I currently have this lens (for use on my T1i), and also have the Kenko 1.4X DGX TC(this is the good one generally recommended for this lens). This combo seems to work to my satisfaction. However, In planning for a rather big trip to some major National Parks in September, I was thinking that I should consider a longer zoom reach....longer than my current 280mm.
    That said, are the 2X teleconverters worth considering? I know what they do to my aperture settings(2X slower). But are there decent ones out there(I'm assuming Kenko or Canon) that will deliver in Image Quality?
    I suppose I could consider selling off my current gear and just purchasing a Canon 100-400L lens. Would that be reasonable? I just need to cover my options before making any further decisions. Thanks
     
  2. AF doesn't work at F8 so you'll need to use MF. AT F8 your small optical VF will be extremely dark and a cruel befuddlement during MF attempts. LV on a tripod is probably your best bet but only useful for landscapes. I'd save up for a 400 4.5L, 300 4L or 100-400L.
     
  3. Your lens is actually a 448mm fl with your current 1.4x converter. You're not taking into account the aps-c sensor of your t1i. Also, I may be wrong about this, but I don't think your camera will have af with the 2x converter since your minimum aperture will be f/8. Plus unless it's really bright, you'll have to pump up your iso quite a bit to get a decent shutter speed unless you plan on using a tripod the majority of the time. Just something to consider.
     
  4. Your lens is actually a 448mm fl with your current 1.4x converter. You're not taking into account the aps-c sensor of your t1i.​
    You're running into one of my pet peeves here. Focal length is not changed by crop sensors, and all it does is confuse people when you say that it does. The cropping effect of the smaller sensor reduces the effective angle of view that you get from your lenses, resulting in an angle of view similar to what you would get from a 1.6x longer lens, but it's incorrect to say that the focal length is actually different. Focal length is a physical property of a lens and you can't change it by putting it on a different camera.
    You are correct, though, that the T1i will not autofocus with an effective maximum aperture of f/8. The OP would have to focus manually.
    2x teleconverters tend to produce less than satisfactory images, but probably still better than what you would get if you shot without the TC and then cropped the image afterward.
     
  5. Yeah, you're correct. I worded that badly I suppose. I realize it doesn't actually change the fl, I should of worded it your lens would be equivalent to a 448mm fl.
     
  6. are the 2X teleconverters worth considering?​
    No.
    selling off my current gear and just purchasing a Canon 100-400L lens.​
    It will be the better option for you in terms of one telephoto zoom covering most situations. Of course, it will weigh 3.0 lbs and extend an additional inch. The lens is also useable with any Canon Extender EF. But, expect dimished results.
     
  7. I appreciate the comments, thus far. Thanks all. Maybe I should just use my Canon SX20IS for all long shots. 20X zoom. Used almost exclusively during daylight. The largest prints I'd make would only be 8X10s anyway. What are your thoughts on this?
     
  8. Maybe I should just use my Canon SX20IS for all long shots​
    A very good choice. At times, I carry the Canon PowerShot G12 as a 28-140mm complement to my DSLR and whatever telephoto prime. Otherwise, it is solely the G12 on leisurely outings.
     
  9. 2x teleconverters tend to produce less than satisfactory images, but probably still better than what you would get if you shot without the TC and then cropped the image afterward.​
    I did some tests a while back – I think it may have been when I had a 50D – to compare the 70~200/4L IS on its own at 200mm, with the Extender 1.4× II at 280mm, and with the Extender 2× II at 400mm. With the 1.4×, more detail was revealed than with the lens alone, but with the 2× no more detail was revealed than with the 1.4×, although results were a bit better than I expected. So I don't consider it worth using the 2× with that lens, expecially since phase-detect AF is lost with all but 1-series bodies.
     
  10. Note that with some brands the aperture change by the extender is not communicated. The AF will be operational.
    This can also be done with Canon by taping off some of the contacts. (Canon advises against that but it works, or so I am told.)
    The results with the x2 III extender aren't that bad by the way. (With the II they're less good. See the mouse over.)
    Kind regards, Matthijs.
     
  11. Matthijs,
    Thanks for comparing the two TCs. You're right, the 2X III is really not that bad at all. Now becomes a question of expense and loss of wider aperture....and loss of AF(?).
     
  12. Robert,
    Have you thought about renting a lens for your trip? LensRentals has a great selection for your Canon.
    http://www.lensrentals.com/for-canon
     
  13. Yes, I have considered renting. But this might give me a good excuse to just go out and purchase one, too. I'm sure that a 100-400mm would get lots of use for my frequent nature shots.
    But.....I could not make such a buy without the sale of my tried and true 70-200/4 IS. Therein lies the dilemma.
     
  14. What are you planning on shooting with such a long focal length? If you are thinking birds etc... you may find that the AF is too slow with a TC (they slow down the AF). If you really need 100-400 on a regular basis then trade your 70-200. But if you will mainly shoot in the 70-200 range then you may want to rent or consider a prime (which are cheaper than zooms) such as the 300 F4 and 400 f5.6
     
  15. "... your lens is actually a 448mm fl with your current 1.4x converter."
    A way to avoid the blow-back about the focal length not changing (which is, by the way, absolutely correct) is to phrase this important point more or less as in the following:
    "... the angle of view provided by your lens is actually equivalent to that of a 448mm fl on full frame with your current 1.4x converter."
    Dan
     
  16. Note that with some brands the aperture change by the extender is not communicated. The AF will be operational.
    If by "operational" you mean "will try to work but may be completely useless." The f/5.6 limit is there for a reason; here's a simplified explanation.
    Phase-detection autofocus essentially samples light from opposite sides of the beam of light being projected into the camera by the lens. If the subject is in focus, the two sensors will see the same thing; if the subject is out of focus, the images seen by the two AF sensors will be shifted relative to each other, with the direction of the shift depending on whether the subject is closer or farther than the focused distance and the magnitude of the shift depending on how far out of focus the subject is (all else being equal).
    As the lens gets slower, this beam gets narrower, and at some point the beam becomes narrow enough that the AF sensors lie outside the beam of light. At this point, obviously, AF no longer works. In general, the farther apart the two samples are, the better the AF system works, but the tradeoff is that this would require a faster lens (and if you've ever wondered why the high-precision AF sensors in some bodies require faster lenses, now you know). f/5.6 is a reasonable compromise between the two. f/5.6 is not a hard-and-fast cutoff; there's a margin of safety in there, which is why a third-party zoom lens that's f/6.3 on its wide end can still autofocus even though it's slower than the supposed requirement of the camera (and such lenses lie to the camera, stating that their aperture is actually f/5.6, to avoid having the AF system shut itself off). But f/8 is a whole stop slower than the camera's designed to use, and you shouldn't count on it working at all; even if it does, don't expect it to be as reliable as with a lens that's f/5.6 or faster.
    FWIW, I once tried using the Canon 1.4x II TC on the 28-135/3-5.5.6 IS USM. (This is not a supported configuration, and can only be used if you're careful to keep the zoom toward the long end of its range; if you zoom back to the wide end, the rear element of the lens will strike the front element of the TC, potentially damaging both.) Since the zoom is f/5.6 at its long end, it becomes f/8 with the TC. The body doesn't know this, because the lens isn't designed for use with a TC and therefore lacks the extra contacts necessary to detect the TC's presence, so the body tries to AF. I don't recall whether I did this with my Elan 7E or 20D, but the end result was that even in good light with a high-contrast target, the AF system simply hunted between near and infinity and was unable to find anything to lock onto.
     
  17. Philip Wilson,
    To answer your question, I'm planning on shooting wildlife in National Parks. Birds being the least of my interests. I'm thinking more like larger mammals such as deer, moose, bears, elk, etc. This entire venture is new to me.
    If I felt my 70-200 with 1.4X TC could handle most of my needs, I'd stop there; as I have this.
    I know that the results of such a combo are good. But is the length(reach0 sufficient? I'm not so sure on that.
     
  18. Large moose are about 6 feet at the shoulder and black bears are 3 to 4 feet. So you could take pictures of people at different distances and see how far away you are before cropping becomes unfeasible. We were taking photos of grizzlies from anything up to 100 feet away with a 300mm lens with decent results.
     
  19. Mike,
    30 yds is pretty close for grizzlies. Were you on foot, or in a car? What park? What season?
    Thanks
     

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