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06-07-2017, 08:36 AM   #1
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1.4 teleconverter - compatible with Sigma 18-300?

Maybe I need some advice and information on compatibility regarding my 1.4 teleconverter. I've been disappointed in the utility of my 1.4 teleconverter. It's terrible on the 60-250, which is almost always on the camera (K-3). Does it produce good images on any zoom? Specifically, how does the teleconverter perform on a Sigma 18-300? (I was thinking about the 18-300 for a better travel lens.)
Thanks for feedback!

06-07-2017, 09:24 AM   #2
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First which teleconverter do you have? There are quite a few "1.4 teleconverters" out there. Some are very good, some are ...... not.

If you are not happy with the results you are getting with your teleconverter with the 60-250 I can assure you they will be far worse with the 18-300. I have no idea if yours will be compatible with that lens (since we do not know what TC you have) but the 18-300 is not a fast lens and I would be surprised if the AF would work with a TC even if they are physically compatible.

I currently have the Pentax HD DA 1.4x teleconverter and use it regularly with the DA*60-250 with very good results.
06-07-2017, 01:42 PM   #3
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Thanks for your comment that it might not do well with the 18-300. If anybody else has experience with this, I'd appreciate hearing about it.

I also have the Pentax 1.4x HD PENTAX-DA AF Rear Converter AW for K-Mount Lenses, which is supposed to be good. It performs very poorly with my 60-250, not producing sharp images. I recall reading someplace (maybe this forum) that the teleconverter is not compatible with the 60-250, so I am glad you are getting good results.

Thanks again,
06-07-2017, 01:45 PM   #4
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QuoteOriginally posted by conbio Quote
Thanks for your comment that it might not do well with the 18-300. If anybody else has experience with this, I'd appreciate hearing about it.

I also have the Pentax 1.4x HD PENTAX-DA AF Rear Converter AW for K-Mount Lenses, which is supposed to be good. It performs very poorly with my 60-250, not producing sharp images. I recall reading someplace (maybe this forum) that the teleconverter is not compatible with the 60-250, so I am glad you are getting good results.

Thanks again,
The Pentax 1.4x TC is definitely compatible with the 60-250mm. Perhaps you lens needs an AF adjustment?


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06-07-2017, 04:37 PM - 1 Like   #5
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QuoteOriginally posted by conbio Quote
I recall reading someplace (maybe this forum) that the teleconverter is not compatible with the 60-250, so I am glad you are getting good results.
You recall incorrectly I think. I was never a big fan of teleconverters and often said so. But I was convinced to try the HD DA 1.4x with the DA*60-250 based on reports here that it worked well. I am very glad I did as it completely changed my mind.

If you are not getting good results then something is wrong as you should be getting good results. Note that AF fine tuning is available and there will be a different profile saved for both the 60-250 and the 60-250 with TC mounted.
06-08-2017, 08:20 AM   #6
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QuoteOriginally posted by conbio Quote
Maybe I need some advice and information on compatibility regarding my 1.4 teleconverter. I've been disappointed in the utility of my 1.4 teleconverter. It's terrible on the 60-250, which is almost always on the camera (K-3). Does it produce good images on any zoom? Specifically, how does the teleconverter perform on a Sigma 18-300? (I was thinking about the 18-300 for a better travel lens.)
Thanks for feedback!
i do not think any teleconverter will please you on a lens with maximum aperture at the long end of F6.3, as the loss of a stop due to the TC will make the native aperture too small for the AF system to work reliably.

you really need to be faster than F6.9 as a combined aperture to get the lens to work, and assuming the aperture is directly variable by focal length, then for lens focal lengths longer than 200mm. this is a best guess, but considering the loss of performance optically and that 200mm on the lens, plus a 1.4x TC gets you just back to 300mm (more or less) you will actually gain nothing. you are better off here to just crop in to betterframe the shot
06-09-2017, 06:57 AM   #7
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Thanks you all for this good information. I will not give up on the teleconverter for the 60-250 and will learn how to adjust the focus. If I even decide to get the 18-300, I won't have any hopes for the teleconverter. Happy Friday,

06-09-2017, 07:53 AM   #8
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not quite answering your question, but...
I use both a pentax and tamron converters occasionally on tamron 28-200 and 75-300 zooms

the images I get are not significantly worse than those taken without the converters

though the k3 seems to allow you to see the shortcomings of the combination more than my older bodies
10-14-2017, 12:13 PM - 2 Likes   #9
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Some of my favourite shots ever were taken with the DA*60-250 and HD DA 1.4 TC.....
K-3 DA*60-250 with 1.4 TC for 350mm
400 ISO ƒ5.6 - 1/1250s -1.3 EV

10-14-2017, 02:12 PM   #10
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Rather than use a TC on a type of lens like 18-300mm, you'd probably be better off to just crop post-process. Better quality-wise and you'd have access to higher shutter speeds, lower ISO, etc.
10-14-2017, 07:48 PM   #11
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QuoteOriginally posted by mikesbike Quote
Rather than use a TC on a type of lens like 18-300mm, you'd probably be better off to just crop post-process. Better quality-wise and you'd have access to higher shutter speeds, lower ISO, etc.
I'd be interested in some one actually testing this hypothesis, rather than just posting it.
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