Tamron 1.4X Teleconverter

Discussion in 'Photography Equipment & Products' started by fmw, Oct 27, 2006.

  1. fmw

    fmw No longer a newbie, moving up!

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    I've never been a big fan of teleconverters. I've always worried about distortion, blurry corners and, of course, loss of light through them. That says nothing about adding more glass and the flare that can be generated that way.

    But this wide angle shooter doesn't like to spend a lot of money for long lenses because I don't use them very often. My shooting style is usually up close and personal. I thought I might try a teleconverter to see if that might add some useful focal length to the long end of my lens arsenal. Who knows, it might work out well.

    [​IMG]

    I chose the Tamron 1.4X for a number of reasons. In the first place, it is a modest, simple 4 element unit that is small, light, and not likely to have as many optical nasties as one of the higher magnification units. It would only lose a single f stop of light. Tamron has a well deserved reputation for producing good optics. Also, it was affordable at a little over $100 from B&H.

    My longest lens is a beauty. It is the 300mm AF Nikkor F4 ED. It is crisp and sharp and has virtually no aberrations that are visible in photographs. So the teleconverter would turn it into a 420mm f 5.6 - certainly a nice addition to the lens collection at a very affordable price.

    New lenses go through a lot of tests at my place before I put them to use. I'm not going to bore you with the details of what I do to test lenses but I will at least deal with the issue of sharpness here. The image below is a newspaper page shot at near minimum focus - around 5' for this 300mm lens - with the Tamron teleconverter in place. Here's the full frame image:

    [​IMG]

    As you can see the setup produces crisp, sharp images with good detail. Remember you're looking at a 72 ppi jpeg. Note that the straight ruler lines on the edges of the newsprint remain straight. That means that this well corrected lens stays well corrected even with the teleconverter in place. No pincushion distortion is visible at all.

    The second image is a blowup of the lower right hand corner of the frame to test for corner sharpness.

    [​IMG]

    This is more than I expected, to tell you the truth. I know the 300 Nikkor is tack sharp in the corners but I didn't think that could be preserved with an inexpensive teleconverter. I was impressed with this result.

    In a nutshell, I consider the Tamron 1.4x teleconverter to be a truly outstanding optical accessory for your long lenses. Yes, you will loose a very slight amount of contrast which you can restore in post processing. Yes you will lose an f stop of light. But the overall ability of this product to produce sharp images is certainly there. It is a keeper.
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That's good to know, thanks.

    I have a Sigma 2X teleconverter...the only time I even consider using it, is when shooting wildlife...and then I put it on my slow telephoto zoom (Vivitar 100-300...now upgraded to Canon 70-300). The quality is not great and the loss of two stops of light is enough to lose autofocus...so this is a manual focus set up for me.

    I have been meaning to...but haven't gotten around to test this. What I really want to know is...which is better; Just using the 70-300 and cropping or getting the extra reach with the 2X TC and not cropping?

    Keeping AF without the TC is certainly an advantage...but if the quality is not too damaged by the TC...it's still a viable option, I think.
     
  3. fmw

    fmw No longer a newbie, moving up!

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    I see no loss of sharpness at all. Not even a little and no distortion either. In order to see the loss in contrast, I had to blow up the image to pixel level and compare it to the same shot made without the TC. The difference was very subtle.

    I tested AF and it worked just fine. My 300 is an older (early 90's vintage) lens and it has funky, slow AF. It isn't one of the snazzy quick silent wave focusing units like we have these days. The lens has a focus limiting ring so that you can adjust it to prevent it from seeking focus endlessly. I didn't need it for the teleconverter. The lens focused the same with the converter as it did without it.

    It is a very impressive product.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I'd be much better off if I had a good lens like the one you have. With an aperture of F4 and a 1.4X...you end up at F5.6...which is the AF limit for most AF cameras. With my set up...at 300mm the lens is F5.6...take away two stops and I'm sitting at F11...no autofocus.

    I think this proves why teleconverters are pretty much only used with good quality prime lenses. Actually, I think that the Canon teleconverters...on work with their telephoto L lenses anyway.

    I'm going to test my set up.

    When you get a change to really use yours, we want to see the photos.
     
  5. fmw

    fmw No longer a newbie, moving up!

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    I plan to take it with me tomorrow. I'm not sure how much shooting I'll do because I have some honey do's to do but I will try to put it to use. I want to test it with the zoom lenses as well. If it is going to act up, it will do so more easily with a zoom than with a simple single focal length lens.

    It will take the long end of my 17-55 f2.8 up to 77mm which is a nice, medium telephoto on the digital. That one is a complex lens. It will be interesting to see if the TC is just too much for it. We shall see.

    I'll try to shoot some newpaper as well with the 17-55 as a comparison.
     
  6. fmw

    fmw No longer a newbie, moving up!

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    That was interesting. I mounted the rest of my lenses on the teleconverter and tested them for AF. The 80-200 f2.8 zoom and the 60mm micro Nikkor worked quietly, quickly and smoothly. The DX lenses (digital image circle) fought with the unit and spent quite a while getting focused. The 17-55 f2.8 zoom, oddly, would never settle down at focus when extended to maximum focal length. I had to back the zoom control off a little to get it to complete the AF cycle. The other focal lengths on the lens were fussy but worked OK.

    Here's the newspaper page shot with the 17-55 f2.8 at a hair under maximum focal length and close to minimum focus.

    [​IMG]

    You can see that this lens exhibits some pincushion distortion. That's pretty typical of zooms and not surprising. The good news is that the TC didn't enhance it. The lens exhibits the same amount of pincushion without the TC.

    Corner sharpness, of course, isn't in the same league as the fixed focal length telephoto. I wouldn't expect that either but, truthfully, I would have expected it to be better than it is. I always assume that lens designs get better with with time. Not always true. This is a fairly expensive lens and I wasn't impressed with the corner sharpness. Again the good news is that the TC didn't make it any worse. It is soft in the corners without the TC as well.

    [​IMG]

    I made the photograph of the TC itself with this lens at maximum focal length. You don't see corner sharpness problems simply because I cropped off the corners. Maybe I'll try the kit lens next.

    This test doesn't say anything bad about the Tamron unit optically. It does point out that fixed focal length lenses outperform zooms but we all knew that anyway. I don't know what causes the AF problem at the long end of this zoom lens but not with any other lens I have but I'll blame it on the TC since I need to blame something on it. :)
     
  7. fmw

    fmw No longer a newbie, moving up!

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    Here you go, Mike. I didn't have much time to shoot and the weather was cold and blustery so I just made a simple demo for you. the first shot is a wide angle shot using my 12-24 zoom. The second shot is just the orange sculpture you see in the wide angle shot. This was done with my 17-55 f2.8 zoom at 55mm with the Tamron TC installed.

    [​IMG]
    [​IMG]

    Both shots were handheld. The first was autofocus and the closeup of the sculpture was manually focused. I think the image quality in a real photograph is pretty decent with the TC. I'm happy I bought it. Sorry I didn't have the energy to haul the telephoto and a tripod but, hopefully, this will give you what you need. Good shooting.
     

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