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  1. #1
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    Question Tele-converters? Safe to use ... or what?

    A lot of new photographers ask about the bane of lensmen … ye old tele-converter (or T/C).

    Yeah, those little 1.4x, 1.7x, 2x or 3x fittings you sandwich between you camera body and the lens you use, supposedly providing you will instant longer lens.

    My advice:

    Do NOT be so quick to buy into that idea. While these cheap additions may seem attractive to the photographer on a budget, the image quality goes to heck, real quick, turning your beautiful 70-200mm f/2.8 zoom shot … into a longer, darker, un-sharp image producer.

    Always consider buying a better lens, first, unless there just is no way you can pop for it.

    The fact is, placing a tele-converter on a 200-500mm f/5-6.3 lens takes away the lens’ infinity focus. Yeah, no kidding. What that means is if you are shooting anything beyond 27 feet from the end of your lens … it is out of focus (OOF). The actual lens focusing mechanism cannot compensate for the additional gap you have just inserted by adding the tele-converter into the mix. So, while you may want to get that bird sitting way up in yonder tree (one hundred yards away) … with your newly created home-made 400-1000mm f/11-13 monster … it will never look sharp. So what's the point? "Yeah, I got the shot!" I don't think you are going to be all that impressed by the result. I know I certainly wasn't, when I did it.

    So, be aware that infinity focus, on many lenses will become unusable, once you add this device to your lens.

    Using the TAMRON SP AF 70-200mm f/2.8 Di LD MACRO, here are a series of shots taken at 10-feet ... @ 200mm (no T/C); 280mm (1.4x T/C); & 400mm (2x T/C). I had to manually monkey around for the flash to have enough pop to maintain the base f/8 aperture (TTL really gets confused when using a T/C, also, so the “pop-up” flash is effectively useless, even if you try to jack up the flash exposure setting. )

    NO T/C
    Name:  70-200-no-tc.jpg
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Size:  317.8 KB

    1.4x T/C
    Name:  70-200-14x-tc.jpg
Views: 125
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    2x T/C
    Name:  70-200-2x-tc.jpg
Views: 120
Size:  236.0 KB

    You need to bear in mind that stopped down to f/8 or tighter, these all are going to look acceptable ... if you try to go with a wider aperture ... then the images degrade (see below):

    2x T/C wide-open aperture
    Name:  70-200-2x-tc-wide-open.jpg
Views: 116
Size:  201.8 KB

    So, use them as you like, but be prepared for the drawbacks. There are a few.
    Last edited by DonSchap; 11-09-2008 at 09:10 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  2. #2
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    perhaps it's the A900 adding to the quality, but I saw this moon shot yesterday on flickr.



    It's the bigma (50-500mm) + 2x TC + A900, hand held + partially cropped.

    I guess the sigma 2x TC works differently for long distances?
    flickr

    Canon 7D - 5D | 550EX - 430EX II - (2) PW FlexTT5 | 24-105 f4L | 70-200 f2.8L IS | 100 f2.8L IS | 50 f1.8 II

  3. #3
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    you just have to know how and when to use them and accept the limitations they may have. there is no point doint pixel peeping indoor tests like that cos thats exactly the situation where TC's are at their worst.

    70-200/ 2.8 +TC17


    105VR + TC17





    300mm f4 + TC17





    they look pretty sharp to me. sure, it's no 300/2.8 or 200-400VR but hey, it's $300.
    Last edited by Rooz; 11-10-2008 at 10:55 AM.
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  4. #4
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    Just depends what lens you hang it off of, I suspect. If the lens was marginal BEFORE the T/C ... I would hazard to say, the IQ is probably heading in the wrong direction AFTER the T/C.

    Just an observation ... but, in MY own experience, a considerable one ... or why mention it at all?
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  5. #5
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    Don, no need to get all pissy. lol

    you presented one view and said
    the image quality goes to heck, real quick, turning your beautiful 70-200mm f/2.8 zoom shot … into a longer, darker, un-sharp image producer.
    .

    i presented another POV and i'll let the IQ do the talking.

    TC's defiantely have some IQ degredation. no one questions that. 1.4 is barely noticeable. 1.7 is ever so slightly notcieable, 2x is starting to be too much and so on and so on.

    however, in saying that, using a 1.7 tc has its advantages IF, and i repeat IF, you know when and how to use them. i think the images above clearly indicate that a TC doesnt degrade IQ that much. if i didnt mention i used one in those shots i doubt you'd ever pick that i did.

    my 300/4 turns into a 6.3 with the TC and if conditions are bright i use it without thinking twice. for less than $300 i have a 500mm lens that produces IQ i'm very happy with. (keep in mind that my 300/4 is also a second hand 10 year old lens for under $1000, so its no exotic piece of glass i'm using it with). the problem comes when people throw the TC onto a pissy kit lens and expect it to be a shortcut to focal length. like i said, use it the right way and they are fantastic, use it the wrong way and you have bad experiences.

    btw: i also have no clue what your talking about with infinity focus. i have never had that problem on any lens i've used the TC on so wasnt aware of that issue.
    Last edited by Rooz; 11-10-2008 at 01:53 PM.
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  6. #6
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    Quote Originally Posted by Rooz View Post
    Don, no need to get all pissy. lol

    you presented one view and said .

    i presented another POV and i'll let the IQ do the talking.

    TC's defiantely have some IQ degredation. no one questions that. 1.4 is barely noticeable. 1.7 is ever so slightly notcieable, 2x is starting to be too much and so on and so on.

    however, in saying that, using a 1.7 tc has its advantages IF, and i repeat IF, you know when and how to use them. i think the images above clearly indicate that a TC doesnt degrade IQ that much. if i didnt mention i used one in those shots i doubt you'd ever pick that i did.

    my 300/4 turns into a 6.3 with the TC and if conditions are bright i use it without thinking twice. for less than $300 i have a 500mm lens that produces IQ i'm very happy with. (keep in mind that my 300/4 is also a second hand 10 year old lens for under $1000, so its no exotic piece of glass i'm using it with). the problem comes when people throw the TC onto a pissy kit lens and expect it to be a shortcut to focal length. like i said, use it the right way and they are fantastic, use it the wrong way and you have bad experiences.

    btw: i also have no clue what your talking about with infinity focus. i have never had that problem on any lens i've used the TC on so wasnt aware of that issue.
    Thanks for your pictures!

    I think it might be a Tamron issue?
    flickr

    Canon 7D - 5D | 550EX - 430EX II - (2) PW FlexTT5 | 24-105 f4L | 70-200 f2.8L IS | 100 f2.8L IS | 50 f1.8 II

  7. #7
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    Rooz,

    Old buddy, old pal ... I suggest you take your 2x or 1.7x and 1.4x T/C and get your hands on a TAMRON 200-500 (Nikon-mount) lens. Mount it up, then try and achieve focus on anything say 50 feet away. If you do happen to get a sharp image, I really do want to hear about it, because then it's off to the repair depot to get mine all fixed up.

    No matter if it was the Canon-mount or SONY-mount, neither lens rendition was able to acheive infinity focus with the addition of a T/C. They just are not built(designed) to tweak focus far enough to compensate for the lengthening of the barrel. It has to do with the design of the lens, itself ... not the T/C. You just cannot use a T/C for anything beyond 27-feet with these type of lenses.

    It's not "gettin' pissy" and all that ... it's getting accurate ... that is that.
    Last edited by DonSchap; 11-10-2008 at 06:29 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  8. #8
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    as i mentioned, i was not aware of the infinity focus issue cos i had never experienced it. that was not a jibe at a sony mount lens. lol besides which, i would never buy nor bother using that lens brother Don. the only tamron you'll ever see me buying by choice is the legendary Tamron 90mm f2.8.
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  9. #9
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    Your commitment to Nikon is ... expensive. I will give you that nod.

    Personally, the level I am shooting at is not as ... exacting ... and as such, I am having a little too much fun with it, as still a hobby. Anyway, as the thread implies ... there are considerable drawbacks to use of these "band-aid" devices and the public should be aware of them, when stepping into this arena.

    Anyway, try the lens ... just for the thrill of being a little daring.

    One of the primary reasons that I purchased a SP AF 200-500mm f/5-6.3 Di LD was because of its extraordinary sharpness ... versus trying to acheive the same shot with a 2x T/C and the 70-200mm f/2.8. There just is no comparison, so the argument is rather silly. The REAL glass is "incomparable."
    Last edited by DonSchap; 11-10-2008 at 06:58 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  10. #10
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    Quote Originally Posted by DonSchap View Post
    Your commitment to Nikon is ... expensive.
    IQ and performance is paramount to me brother Don. i prefer to save my pennies and buy one great lens rather than have 3 ok ones.

    i accept that tamron has its place in the market which is affordable quality. its just not my weapon of choice. thats not a criticism; diffrent strokes for different folks. i have owned the tamron 17-50/2.8 and the 90/2.8 aswell btw so i know exaclty how well, (or not), they perform.
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