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Old May 16, 2007, 7:12 PM   #1
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I have a Sigma EX 80-400 f4.5-5.6lens that I use for wildlife. It's a wonderful lens, capable of superb clarity and image quality, but I find it still needs a bit more reach. I'd love to be able to use a 2x TC on it, but from everything I've read, 2x converters just cost too much in terms of image quality and light, so I've decided a 1.4x will have to do. Besides, my eyes aren't what they used to be, andI trust the camera's AF more than my own poor ol' eyeballs to give me an accurate, clear focus.

I purchased a Kenko 1.4x on the advice of a fellow photog who said he'd had good luck with his, but I've had horrid results. Most of my photos are blurry, even though the AF still works - or at least it "tells" me it does - at f5.6 (f6.3 with the converter installed). I've seen wonderful photos others have taken with 1.4x converters, and I'm wondering if I just got a bad TC, or if I need to get rid of the Kenko and try a different brand, perhaps one made by Sigma for my lens?

Does anyone here use a Sigma 1.4x converter? If so, what kind of results have you had with it?

Rocky
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Old May 16, 2007, 7:43 PM   #2
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can u post some sample images

and regarding sigma teles

http://forums.steves-digicams.com/fo...mp;forum_id=65
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Old May 16, 2007, 10:11 PM   #3
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here are a couple of examples. these arethe BEST i've gotten... most of the rest were deleted as soon as i downloaded and looked at them! it seems 90% or more of the shots i take with the Kenko wind up in the dumper, and the few i do get that are "keepers" are not only few and far between, but they're still not as clear and sharp as what i've seen taken with other converters.

both of these were also taken at fairly long ranges (if they were close, i wouldn't need a converter! :lol... the first at about 60 yards, the second at 80-100. i don't expect crystal clarity from shots at those ranges, but even the shots i've taken at shorter distances are soft and poorly focused.




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Old May 16, 2007, 10:33 PM   #4
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squirl, what kind of shutter speeds are you using?? I'm at work and can't see your pics. also, are you using a tripod? If shutter speeds are lower than about 1/500 second it could be motion blur even with IS/OS. I'll try to check out your pics when I get home. Actually at f/8 at the 400mm setting unless you have a 1 series camera it shouldn't autofocus but, some do as they don't indicate the TC is there. Your's may be one of those.

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Old May 16, 2007, 10:40 PM   #5
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Two remarks:

1. A teleconverter works best in bright light (sunshine) and will perform poorly in overcast days because of the resulting lost of contrast inherent in adding any TC

2. The Kenko must be a generic one since it does not transfer the proper aperture - A 1.4x TC should bring the aperture to f/8 (1-full stop) and not only a 1/3 of a stop @ f/6.3! So even though the AF might work it may not be up to spec :
-> At the correct f/8 aperture the camera AF should be disabled (since it can not guarantee focusing accuracy)

On the 1D MrkII only the center AF point work down to f/8, all the rest are disabled
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Old May 16, 2007, 11:01 PM   #6
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djb wrote:
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squirl, what kind of shutter speeds are you using?? I'm at work and can't see your pics. also, are you using a tripod? If shutter speeds are lower than about 1/500 second it could be motion blur even with IS/OS. I'll try to check out your pics when I get home. Actually at f/8 at the 400mm setting unless you have a 1 series camera it shouldn't autofocus but, some do as they don't indicate the TC is there. Your's may be one of those.

dennis
Dennis,

i shot one of these at 1/500, the other at 1/1000, so shutter speed alone isn't the problem. i've had the same results even shooting subjects that weren't moving (i didn't use a tripod for these... tracking birds in flight from a tripod is most oftenan exercise in futility). supposedly the AF should work on my 30D as long as i have a max aperture of at least f6.3, and my Sigma is f5.6 at 400mm.i lose a stop with the TC, which makes it a 6.3 lens, but AF should still work... and i still get the usual AF indications in the viewfinder.
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Old May 16, 2007, 11:06 PM   #7
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NHL wrote:
Quote:
Two remarks:

1. A teleconverter works best in bright light (sunshine) and will perform poorly in overcast days because of the resulting lost of contrast inherent in adding any TC

2. The Kenko must be a generic one since it does not transfer the proper aperture - A 1.4x TC should bring the aperture to f/8 (1-full stop) and not only a 1/3 of a stop @ f/6.3! So even though the AF might work it may not be up to spec :
-> At the correct f/8 aperture the camera AF should be disabled (since it can not guarantee focusing accuracy)

On the 1D MrkII only the center AF point work down to f/8, all the rest are disabled
i sorta figured bright light was a must for good pics with the TC, but even in bright light, it seems most of my shots come out poorly. maybe i'm expecting too much, but i've seen such nice results with other TCs, i'm beginning to wonder...

i believe the Kenko is the same as the Tamron, just different markings. if my lens is f5.6 at max aperture, the TC would only bring it down to f6.3, no? and since i only use the center AF point anyway, i don't know if my 30D disables the rest or not...

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Old May 16, 2007, 11:07 PM   #8
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squirl, as I mentioned and NHL mentioned, with a f/5.6 and a 1.4X TC your 1 stop in aperture brings it to f/8 not f/6.3. And on your 30D it should not autofocus unless, like we said, your TC is not indicating to the camera so it appears to the camera as f/5.6 and it will autofocus. Probably slowly with a lot of hunting (unless it is very bright light or high contrast) and as NHL mentioned maybe not too accurately. Handheld at 1/500 or even 1/1000 you can still get motion blur.

dennis
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Old May 16, 2007, 11:10 PM   #9
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squirl, one other thing, not to dis you but you mentioned your old eyes aren't that good so, it appears you may be over 50 or so and maybe your hands aren't as stable as they used to be. Just another thought.

dennis
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Old May 17, 2007, 12:35 AM   #10
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djb wrote:
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squirl, one other thing, not to dis you but you mentioned your old eyes aren't that good so, it appears you may be over 50 or so and maybe your hands aren't as stable as they used to be. Just another thought.

dennis
does 50 mark the cut-off point for steady hands? yikes!:O no, that's not the problem. my eyes aren't as good as they used to be, but my hands arestill plenty steady... i'm just beginning to wonder if the communication between lens and camera is working properly with the TC in place... it does autofocus, though not as fast as normal, even in bright light, and it thinks my aperture is f6.3 when thecamera is setat 5.6... leastwise that's what it records in the EXIF data... something's fishy somewhere...




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