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03-17-2016, 10:30 AM   #1
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Are Teleconvertors of no use on APS-C bodies?

Hi All.

I have come to enjoy many of Tony Northrup's posts on Youtube, but one that had me puzzled. One of his videos suggests (he is talking Canon/Nikon of course) that there is no reason to use a TC unless one is using a full-frame body. I had been kicking around getting the new Pentax TC to use with the 150-450, on my K3 or Kiis. Northrup suggest the sensors are packed so tightly on an APS-C body that there is no image gain with a TC. My own experience with my 600mm f5.6 A + 1.4-L would seem to support that finding although I thought it might just be a bad teleconverter. So is it simply better to crop or use the teleconvertor on a Pentax APS-c body?

Doug

03-17-2016, 10:49 AM   #2
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I suppose Tony Northrup is right is you consider that most current Canikon FF have less pixel density than their APSC counterparts. That wouldn't be so true when using a Canon 5Dsr / D810 or K-1.
03-17-2016, 11:16 AM   #3
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I'm not sure what Tony means by that. I use a TC on my long lenses on my APS-C DSLRs to get extra length even with the crop narrowing the angle of view.
03-17-2016, 12:25 PM   #4
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QuoteOriginally posted by wtlwdwgn Quote
I'm not sure what Tony means by that. I use a TC on my long lenses on my APS-C DSLRs to get extra length even with the crop narrowing the angle of view.
Same here, am using a 1.4x with my Pentax 55-300.

03-17-2016, 01:04 PM - 1 Like   #5
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Check out this comparison of cropping vs tc:

Pentax-DA 1.4x AW AF Rear Converter Review - DA 1.4x, A 1.4X-S, and Tamron Compared | PentaxForums.com Reviews

QuoteOriginally posted by stemked Quote
600mm f5.6 A + 1.4-L would seem to support that finding
At really long focal lengths you start to get diminishing returns because proper focus and perfect stability becomes harder and harder. That could potentially be a factor in your case, rather than the TC itself. (plus there's diffraction)

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03-17-2016, 01:12 PM   #6
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I've been using a Sigma 2x APO EG teleconverter with a Pentax-M 200mm/f2.5 on a Pentax KS-2. I'm noticing a bit of image degradation when compared to the 200mm alone - it's truly a wonderful lens - but I'm uncertain whether that's because of the teleconverter or my technique. (I've been doing handheld only at this point, which is pushing things, I know, for a combined 600mm equivalent. Haven't had a chance to play with it on a tripod as yet - have only had the combination about 10 days.) If I nail the focus and keep the shutter speed up, the degradation is really only noticeable when I'm pixel-peeping. I've gotten several very nice shots that I'd be happy to print and frame. So, for me, the teleconverter is worth it at this point.
03-17-2016, 01:15 PM   #7
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And there's atmospheric distortion at infinity as well.
03-17-2016, 03:26 PM   #8
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QuoteOriginally posted by stemked Quote
Hi All.

I have come to enjoy many of Tony Northrup's posts on Youtube, but one that had me puzzled. One of his videos suggests (he is talking Canon/Nikon of course) that there is no reason to use a TC unless one is using a full-frame body. I had been kicking around getting the new Pentax TC to use with the 150-450, on my K3 or Kiis. Northrup suggest the sensors are packed so tightly on an APS-C body that there is no image gain with a TC. My own experience with my 600mm f5.6 A + 1.4-L would seem to support that finding although I thought it might just be a bad teleconverter. So is it simply better to crop or use the teleconvertor on a Pentax APS-c body?
Doug
Hello Doug,
I have the Pentax 1.4xTC which I've used with the 150-450 on my K-3 II for birding, and it does help a lot in filling the frame especially when shooting small birds, but the down side is that getting good shots handheld is problematic and requires shutter speeds up around 1/1600...for me at least. Others may have a steadier hand.
If you have any experience with shooting small birds you will know that often you can't get close enough to get a reasonable size in the frame, and cropping such a small subject does lose IQ, so if you can hold it steady, the 150-450 + 1.4xTC can be a good solution.

Cheers,
Terry

03-17-2016, 03:30 PM   #9
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https://www.pentaxforums.com/forums/122-lens-clubs/294721-post-your-hd-pentax...-pictures.html

Have a look at this thread and you will see some of those terribly degraded images that PF photographers are making with the Pentax 150 -450 and the 1.4TC
03-17-2016, 03:48 PM   #10
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QuoteOriginally posted by Murra54 Quote
https://www.pentaxforums.com/forums/122-lens-clubs/294721-post-your-hd-pentax...-pictures.html

Have a look at this thread and you will see some of those terribly degraded images that PF photographers are making with the Pentax 150 -450 and the 1.4TC
But that thread has actual examples. Not just people talking...
03-17-2016, 05:07 PM   #11
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Now that the K-1 is here, I'm hoping that Pentax release a new 1.4 TC that is fully FF compatible - a DFA 1.4 WR TC. Such a TC would make a lot of sense.
03-17-2016, 05:55 PM   #12
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Hi stemked,

Personal experience tells me this proposition does not hold up. I've been shooting birds with Pentax bodies, premium ultra tele primes, and a variety of quality TCs for over 10 years. During this time, the bodies I've used have increased from 6, to 10, then 14, 16, and finally 24 MP, and my results have gotten progressively better, not worse as would be expected if this principle of more pixel density + TC use were true. I'd have expected that a 4x difference in pixel density would really show up, but I actually get consistently better detail and images with my 16 and 24 pixel bodies than I ever did with the 6 and 10 MP bodies.

But why even take my word for it. Mount one of your super teles and a TC on a sturdy tripod and take a series of shots of the same subject in good light (and a nice high shutter speed) with your K5 and K3, then pick the best from each body. If this principle is true, then the 1.5x difference in pixel density should show you consistently degraded images with the K3. If not, then believe your eyes, not some guy making what might seem like a logical argument on the internet.

Scott
03-17-2016, 06:04 PM   #13
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I'd say he got it the wrong way around. Why put a teleconverter on a full frame camera when you could just put the native lens on a crop body and get similar results without losing 1EV?
03-17-2016, 06:41 PM   #14
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Anyone who thinks they can reliably hold a lens equivalent to 600mm, seriously needs to rethink that decision. Don't take my word for it. Take a few images on a sturdy tripod with a 2 second delay, and see if you can match it hand held. That will limit the un-relability of looking at what other people can do, and show you what you can do.
03-17-2016, 06:43 PM   #15
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QuoteOriginally posted by normhead Quote
Anyone who thinks they can reliably hold a lens equivalent to 600mm, seriously needs to rethink that decision. Don't take my word for it. Take a few images on a sturdy tripod with a 2 second delay, and see if you can match it hand held. That will limit the un-relability of looking at what other people can do, and show you what you can do.
Yep!

I have actually managed to handhold an 800mm telescope on my K-50 (1200mm eqv.) but I was kneeling one knee on the ground and the telescope balanced on my knee.
I think it's time to make an adapter to use this on a monopod as the tripod is too swear big most of the time.
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