Results 1 to 17 of 17

Thread: Is it normal? Zoom lenses that does not seems to zoom to correct magnification.

  1. #1

    Default Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    I was looking at some teleconverter lenses for my S5IS

    Alan photo has one that is 3X and John3:16 has one that is 2.5X, these are their third party lenses.

    I tried them on but both with different magnify show little enlargement. I tried with max zoom and no zoom and the magnification look the most 1.5-1.8 times zoom from my naked eye. So is this normal?

    Or really to get a true 2x zoom power, I really have to pay more to get a canon original teleconverter lenses?

    Expert please advice. Thanks.
    Last edited by BlindSpot; 7th July 2008 at 05:17 PM.

  2. #2

    Default Re: Is it normal? Zoom lenses that does not seems to zoom to correct magnification.

    Not sure about that much of a claimed zoom power but my 1.5 is working just fine

  3. #3

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by BlindSpot View Post
    I tried them on but both with different magnify show little enlargement. I tried with max zoom and no zoom and the magnification look the most 1.5-1.8 times zoom from my naked eye. So is this normal?
    why don't you take a picture, and then compare?

    btw, zoom should AREA, not height or width, based on my understanding

    so math should tell you that magnification ratio of linear values will be roots of the magnification ratio

    i.e. root 3 or root 2, which is around 1.4 to 1.8.. i think this is the problem.

  4. #4

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Oh, if that's really the case, then it might explains it. So I have to square the multiplier value stated, right?

    Meaning a 2X teleconverter will not get you a picture enlarged by 2 times. Did I get it correct?

  5. #5

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by BlindSpot View Post
    Oh, if that's really the case, then it might explains it. So I have to square the multiplier value stated, right?

    Meaning a 2X teleconverter will not get you a picture enlarged by 2 times. Did I get it correct?
    it will.

    don't you remember math? if square b has twice the length of each side of square a, then square b will be four times the area of square a.

    you should be getting original frame's (before TC) framing, center cropped out and magnified by 2. but if say, you have a lamp in your picture, it should not appear to have twice the height using a 2x tc. you will have root 2 times the height.

  6. #6

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by night86mare View Post
    it will.

    don't you remember math? if square b has twice the length of each side of square a, then square b will be four times the area of square a.

    you should be getting original frame's (before TC) framing, center cropped out and magnified by 2. but if say, you have a lamp in your picture, it should not appear to have twice the height using a 2x tc. you will have root 2 times the height.
    Now, I am really confused.

    So let say a normal pic without teleconverter and the object appear on a pic taking up 1/2 the area on photo, after that when i put on the teleconverter with 2x multiplier, will the object multiply it's size by 2 times and fill out the whole photo.

    What I understand is the 2x should be referring to the distant being multiplied, but then since it's relative the object should multiply by 2 times right? Meaning 2s time length and breath wise.

    This is at best the example i can try to explain what I wanna ask. I have taken picture but unfortunately deleted them.

    Sorry for sounding like an idiot as I am really new to higher level photography. I tried doing google for it but can't find any good explanation on it.

    If not I can show you guys what i mean.

  7. #7
    Member Parka's Avatar
    Join Date
    Nov 2005
    Location
    Singapore, Singapore
    Posts
    1,067

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    I thought the zoom is the multipler for the focal length?

    28mm with a 2x zoom should go to 56mm.
    Whether or not the object in the photograph has doubled in size should be calculated in other ways.

  8. #8
    Member
    Join Date
    Jan 2005
    Location
    Singapore
    Posts
    1,095

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by night86mare View Post
    it will.

    don't you remember math? if square b has twice the length of each side of square a, then square b will be four times the area of square a.

    you should be getting original frame's (before TC) framing, center cropped out and magnified by 2. but if say, you have a lamp in your picture, it should not appear to have twice the height using a 2x tc. you will have root 2 times the height.
    Magnification is almost universally specified in linear terms. A 2x teleconverter should give, focused at infinity, 2x linear (or 4x areal) magnification.

  9. #9

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by LittleWolf View Post
    Magnification is almost universally specified in linear terms. A 2x teleconverter should give, focused at infinity, 2x linear (or 4x areal) magnification.
    lol. was just guessing.

    you're the man, so i guess we'll take your word for it

    a quick search on wiki also says the same thing

    teleconverter article

    The use of a 2 teleconverter (or doubler) gives the effect of using lens with twice the focal length. It also decreases the intensity of the light reaching the film by the factor of 4 (an equivalent of doubling the focal ratio) as well as the resolution (by the factor of 2).
    from wiki:

    300mm view


    300mm view with 2x teleconverter (notice that the image is darker too)
    Last edited by night86mare; 7th July 2008 at 08:57 PM.

  10. #10

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by night86mare View Post
    lol. was just guessing.

    you're the man, so i guess we'll take your word for it

    a quick search on wiki also says the same thing

    teleconverter article



    from wiki:

    300mm view


    300mm view with 2x teleconverter (notice that the image is darker too)
    Great find.

    Okay reference to the pic above, you can estimate that the lighthouse have been magnified 2 times with a 2X teleconverter.

    Well, now this is what I experienced. With the 3X and 2.5X teleconverters (third party teleconverter the retailer recommended to me) on my S5IS does not seems to give at least 2 times magnification now matter at which S5IS zoom level. The pics taken of the subject on same zoom level are never magnified by 2 times. The most i estimate is between about 1.7-2.0 , thus my questions is whether is this normal.

    Really, is it because they are third party (both different brand too) thus not compatable to use on S5IS? And because of this that's why the resulted pic is never more than 2 times the magnification? So in order for S5IS to experience 2 times of it's native 18x zoom (meaning about 36x zoom) the only way is to buy cannon's teleconverter instead?

    Hope you all get what I want to ask. Sorry the previous posts I made is confusing or unclear. I wish this post is clearer on what I am really trying to find out.

  11. #11
    Member
    Join Date
    Jan 2005
    Location
    Singapore
    Posts
    1,095

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by BlindSpot View Post
    3X and 2.5X teleconverters (third party teleconverter the retailer recommended to me) on my S5IS does not seems to give at least 2 times magnification now matter at which S5IS zoom level. The pics taken of the subject on same zoom level are never magnified by 2 times. The most i estimate is between about 1.7-2.0 , thus my questions is whether is this normal.
    Get used to the fact that "technical specifications" nowadays are sometimes not grounded in properties of the product, but the whims of the marketing department. (The marketing people may not even know what the specs mean.)

  12. #12
    Member
    Join Date
    Jan 2005
    Location
    Singapore
    Posts
    1,095

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by night86mare View Post
    300mm view


    300mm view with 2x teleconverter (notice that the image is darker too)
    Minolta XD-7/XD-11 viewfinder?

  13. #13

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by LittleWolf View Post
    Minolta XD-7/XD-11 viewfinder?
    i won't know, i lifted it from wiki.

    thought it was a good way to demonstrate

  14. #14

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by BlindSpot View Post
    Well, now this is what I experienced. With the 3X and 2.5X teleconverters (third party teleconverter the retailer recommended to me) on my S5IS does not seems to give at least 2 times magnification now matter at which S5IS zoom level. The pics taken of the subject on same zoom level are never magnified by 2 times. The most i estimate is between about 1.7-2.0 , thus my questions is whether is this normal.
    can you post up pictures with exif here?

    just use auto mode, and then take one at a partiuclar focal length, add the teleconvert, take another one. post both up here.

  15. #15

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    Quote Originally Posted by night86mare View Post
    can you post up pictures with exif here?

    just use auto mode, and then take one at a partiuclar focal length, add the teleconvert, take another one. post both up here.
    Sorry, I deleted them. I should have kept them, but at the point of time I assume that's normal thus did not thought about keep them to show to you guys when asking this question.

  16. #16

    Default Re: Is it normal? Teleconverter that does not seems to zoom to correct magnification.

    easy to reshoot anytime.. unless the TC doesn't belong to you.. well can always go to shop and test again.

  17. #17

    Default Re: Is it normal? Zoom lenses that does not seems to zoom to correct magnification.

    Okay, will try again.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •