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Thread: Remove vignette by using a teleconverter?

  1. #21
    Moderator Octarine's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    Quote Originally Posted by Mythmaker View Post
    I'm not really sure about the degradation part actually. I know by nature the TC degrades the image quality for EF frames designed for EF use. But so far from what I have seen over the internet, mounting the 1.4x TC on Sigma 10-20 and a modified Canon 10-22 does really improve the quality by a bit, giving it slightly more contrast and making it sharp throughout (otherwise corners are soft). I'm thinking that TC might actually improve performance for mounting EFS/EF lens designed for Crops on FF, but if anyone had tried it out (using TC on EFS lens on FF) please feel free to correct me
    Rent a TC and do some systematic tests in controlled environment. We are all eager to see the pics
    EOS

  2. #22
    Member Mythmaker's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    Quote Originally Posted by Octarine View Post
    Rent a TC and do some systematic tests in controlled environment. We are all eager to see the pics
    Yep I'm doing that as soon as I can find time to head down to CRC to rent a teleconverter lol. Maybe tmr noon or something

    Will update here on my findings when I have a result

    EDIT:
    I smsed CRC, turns out they ran out of stock for 1.4 TC lol. Guess this will have to wait till further notice...
    Last edited by Mythmaker; 8th February 2013 at 10:46 PM.

  3. #23

    Default Re: Remove vignette by using a teleconverter?

    I am sure enough Kenko TC will work, but not the first party themselves.

  4. #24

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    I have worked with teleconverters with a Canon AF 500mm f/4 IS USM mounted on a Canon 1D Mark III before, and there is clear difference in image quality when using the lens as it is, and with various teleconverters.

    I am skeptical of your purported observations, so I would be interested to hear of the results of your experiment.

    I'd probably stick to cropping anyway.
    KF Photography
    Thanks for viewing!

  5. #25
    Member Mythmaker's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    Haha, I'm skeptical of it myself as well lol! But it's sure mind-boggling that the image of Canon 10-22 and Sigma 10-20 improved with a TC on a FF.

    Here's a 10-22mm post by engrmariano @ 16mm without a TC:
    http://www.clubsnap.com/forums/revie...ml#post6993765

    First observation is that corner is totally soft; PS cannot enhance details there are simply not there.

    This is with a 1.4 TC:
    Newton Ave 9.18.2010 | benjacobsenphoto.com

    The first 2 shots are with a 7D and 10-22, the rest are with the 5d2, 10-22 and 1.4x TC. The first observation is that corners are sharp. I have verified with the photographer, he confirmed that without a TC, the corners are very soft like what bro engrmariano had shot. With a TC, everything changed; it became sharp throughout.

    As for the sigma, it's all over the net (the combination with Kenko DG 300). Here's the thread that was posted on CS:
    We all know the Sigma 10-20 won't work on a 5D2 right? ... Wrong! - Canon Digital Photography Forums

    Maybe I'll just get a Kenko DG300 next Wed to play around :P
    Last edited by Mythmaker; 9th February 2013 at 08:23 PM.

  6. #26
    Member Mythmaker's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    Just a quick update. My friend had helped me buy the kenko Pro DGX300 1.4, $227 from SLRR.

    Initial impression is good. Vignetting observed from 18-100. Vignetting completely disappears after 100mm. Optics at 270 looks the same to my eye at a glance as without the TC. Auto focus works at all focal length, f9 on my 5d3. Managed to focus in low light, as in 1/10, f9, ISO12800 level of low. But need contrast, at above average level (white vs blackish grey)

    Will start test charts when I have the time over the next few days. Hopefully able to test 10-22 with the TC on my 5d3 by next weekend as well before I go for ICT.

    Overall, quite happy with it. A cheapo zoom lens with IS/VC/VR/OS would cost $500+ anyway, and it's f5.6. Only 1.3 stops away from my current config and allows me to use my 10-22 on my mark 3 lol.
    Last edited by Mythmaker; 13th February 2013 at 08:37 PM.

  7. #27
    Member Mythmaker's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    My ISO12233 chart isnt ready, so I took some shots on my focus chart instead.

    The left side is w/o TC, right side is with TC:

    Center (f9):


    Center (f13):

  8. #28
    Member Mythmaker's Avatar
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    Default Re: Remove vignette by using a teleconverter?

    Corners (f9):


    Corners (f13):


    Some quick thoughts:
    Center sharpness retains! Corner takes a dip. Contrast drops all around. 1 stop down seems to be a huge improvement for TC, corner wise. But translated to the field, you probably can't see a diff, unless you go beyond 50% crop. Only thing that's really noticable is the drop in AF speed under low light. With adequate light, no noticeable difference is felt actually. This is getting exciting heehee.

    Will test out in the field if possible over the weekend.

    Oh ya, vignette at 18mm. Disappears at 100mm as mention.

    Last edited by Mythmaker; 13th February 2013 at 11:11 PM.

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