Using a 2X TC on a f4 lens?

Discussion in 'Canon EOS' started by robert_thommes|1, Mar 3, 2014.

  1. I understand that using a 2X teleconverter on my Canon 70-200 f4 IS USM will disable any hopes of using AF. And...will also give me a max. aperture of f8. I can probably live with the f8; as most shooting (Yellowstone) will be in daylight. Will my T2i still offer the white dot or beep MF shooting assist aid? And just how practical is this combo in the field anyway? I'm trying to extend my range with a minimum of expense. No way I can afford the lens that I'd really like, and I'd prefer not to rent(but could). I once used a 1.4X TC on this lens, but was unimpressed with the mere additional 80mm that it gave me; though the IQ results were good. Using a 2X TC and getting me out to 400mm would be ideal. But is it practical?
    And how much IQ will be depreciated? And if a good idea, which specific TC would be your recommendation.
    I also have a 55-250 STM lens, and a Canon SX50. Would these be better options than the 2X TC on the DSLR lens?
    Thanks for helping out.
  2. It will work with focus confirmation (the little green light) not sure if the beep and focus spot will also indicate you've gotten focus.
    Your lens actually isn't too bad with the Canon 2x extender version II or newer. I have the version I and will use it in a pinch and I'd rate it as acceptable. Definitely better than shooting at 200mm and cropping.
    Why don't you rent a 2x from Lens Rentals or Borrow Lenses and see if it's up to your standards?
    BTW, I have no experience with aftermarket extenders, but I'm sure you'll get some responses advocating those as well. Some will autofocus, albeit slowly, at f/8 with some cameras.
  3. Nope. Doesn't work that way. You will NOT get manual focus confirmation via the white/green light and beep on a T2i (or any APS-C body) with a lens/TC combination slower than f5.6.
    You might get (slow) AF using live view. That works with my Tamron 70-300/4-5.6 and a Tamron 1.4x TC on my 7D.
    Obviously the best TC is the Canon, but it's expensive. Try the Tamron. Optical quality should be OK
    I think the SX50 might be your best bet if you're not looking to make poster sized exhibition prints. I've been very impressed with the results from mine.
  4. Bob,
    I guess that's the response I was expecting (about the TC use), and hoping for (the use of my SX50).
    Several years ago when we went there I used a SX20. I just tried to download those images from my CD/DVD, and couldn't do it. I wanted to see how those images worked out. Got a message " No new pictures or videos were found on this device".....the device being my disc. I know that they're on the disc.
  5. A CD/DVD should not degrade in a few years. I have CDs from 15 years ago that read fine. I recently had trouble reading a 20 year old 3.5" floppy, but one of my old systems did read it OK (while another reported disk errors).
    I'm not quite sure what " No new pictures or videos were found on this device" means but it sounds like whatever software you're using recognized the disk. Not sure what "new" means but it suggests maybe you'd already downloaded them via the software you are using. What does Windows Explorer say?

    If it's a read error, try another CD/DVD drive and see if you can read it. If not just Google "cd dvd data recovery" and you'll find a bunch of software that might help you out.
    I have some comments on data preservation on my website at
  6. Bob is anyone surprised?
    I didn't check my facts before I spoke, so I'm going to go wash my mouth out with some Aberfeldy single there!
  7. Got a message " No new pictures or videos were found on this device".....the device being my disc. I know that they're on the disc.
    The use of the word "new" does seem interesting. Lightroom has an option to not import duplicate copies of photos that have previously been imported. The language would seem to indicate that the software thinks the images are already on the system.
    Alternatively it may just mean that the software does not recognise the images as a valid image file format, either because the files are corrupted/invalid for the format or because the software does not support that format. The latter occurs with RAW files either because the particular RAW file format was developed after the software was released or because the camera (and its RAW format) are so old that the software maker ceased to support it or never supported it at all.

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