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09-12-2008, 09:17 AM   #1
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where's the tele extender topic

I think a recent email from Pentax Forums said there was a tele extender forum somewhere.

Where is it?

Are any of the tele extenders for Pentax as nearly good as those for Canon (which are/were superb) ?

Are any of the current tele-extenders well made? (build quality was always in the past Vivitar/Sigma/Tamron's downfall, but Soligar did ok).

09-12-2008, 09:24 AM   #2
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https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...rter-pics.html

massive thread, the tamron is supposed to be good
sigma have a few which i believe are ok, but only work w/ Sigma lenses
09-12-2008, 10:17 AM   #3
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Not a forum, exactly, but a new section in the lens review database:

Pentax Lens Review Database - All Geninue Pentax Teleconverters

Don't get your hopes up -- there are exactly -zero- reviews in there so far. C'mon folks, some of you must have one to review!
09-15-2008, 04:17 AM   #4
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I am not sure you have looked at all teleconverters

Check the third party lens reviews also

There are reviews for the sigma ones. I know, I wrote them.

I have had trouble entering les reviews lately, but still have to do ones on the Takamur 2x, Pentax 1.7x AF, and 2 different vivitars

09-15-2008, 01:24 PM   #5
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I also talked about Promaster 1.7x AF TC along with some discussions on Tamron 1.4x Pz-AF TC in this thread:

Promaster 1.7x AF TC Discussion Thread

And I cover the PF in using Tamron 1.4x in Purple Fringe with Tamron 1.4x Pz-AF on Tamron lens
09-16-2008, 01:33 PM   #6
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The Pentax 1.4x-L converter is about as good as a tc can be. No visible image degradation on those lenses, it fits. The 2x-L is similar with only a very slight loss of image quality. The next best things are the 1.4x-S and slightly behind the 2x-S. The 1.4x-S is hardly any worse than the L-modell (yes, Pentax has "L glass" too), the 2x-S is noticeably behind the L equivalent, but still very good.

All the Pentax tele converters are old and support only A-functionality, but no AF! This is their main drawback. For AF you would need the Pentax 1.7x AF adapter, which was intended to convert MF löenses to AF functionality, but can be "misused" as a plain tc with good quality. The Kenko 1.5x tc is a good third party choice , which works fine with many lenses. The Sigma 1.4x APO tc is even better, if combined with the few lenses, it is dedicated to. In my own experience the Sigma 2x APO is considerably worse, than the 1.4x APO - but I have seen photographs (Lowell?), which testify, that it can be of very high quality, too. The Sigmas (quite as the Pentax L-modells) don't work with all lenses, because they have a protruding front lens element, which collides with the back element of many lenses.

I have all of the above mentioned modells and can only report my own, personal experiences, so take that with a good portion of mistrust...

Ben
09-16-2008, 02:02 PM   #7
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Are there any TC's that report focal length correctly? In other words are there any that allow the shake reduction to compensate properly?
09-16-2008, 02:09 PM   #8
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QuoteOriginally posted by audiobomber Quote
Are there any TC's that report focal length correctly? In other words are there any that allow the shake reduction to compensate properly?
not to my knowledge. Perhaps the new Pentax SDM tc will do that.

Ben

09-16-2008, 02:11 PM   #9
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No intelligent FL multiplier reporting TC spotted yet... (AFAIK) But with common ones ranging from 1.4-2.0 the SR error is not the worst I guess- and if You focus manually You can as well trick Your camera telling it that a legacy lens was attached (mask contacts)- but there seems no real-world use for it.
Best and happy (tele)converting, JR
09-16-2008, 02:18 PM   #10
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QuoteOriginally posted by audiobomber Quote
Are there any TC's that report focal length correctly? In other words are there any that allow the shake reduction to compensate properly?
Yes, the manual focus TC can do that. Or if you switch the body to MF as reps has replied. I once used a Tamron 2.x TC requiring manual focusing and I manage to shoot in 600mm with fully engaged SR at 600mm in

Tamron-F Tele-converter 2x KR MC4 -- 600mm Tamron Lens - Hin's Tech Corner.

But for the AF one, your option is turning a AF lens to MF to gain SR seem too much a compromise. Perhaps when using a TC with a prime tele on tripod, that inaccurate SR is not an issue if you use it on tripod with SR off
09-16-2008, 02:23 PM   #11
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QuoteOriginally posted by audiobomber Quote
Are there any TC's that report focal length correctly? In other words are there any that allow the shake reduction to compensate properly?
At this time no, the TCs don;t report focal length properly, they are passive feed through of lens information.

although this is a little restricting for the shake reduction, on the K10D and possibly the K20D there is another real issue. Also fed through directly is lens apature, and it assumes the camera really does not care about apature only what it thinks is connected and the light. While that may have been true for older Pentax DSLRS, I was quite shocked by the K10D performance with manual apature lenses, and aslo with teleconverters. the exposure is all over the map. It is related to the specific focusing screen used int he K10D (and I assume the K20D) The focusing screen introduces errors in to the metering. It appears that pentax has corrected this in software for "A" lenses by compensating with a "fudge factor" for the open apature metering. The real problem is now when you put a TC on the camera, it applies the wrong fudge factor because it thinks the lens is faster than it really is.

I ran a test some time back, and posted the results as a closing out comment to a rather heated argument between myself and another forum member

I have attached a link here

https://www.pentaxforums.com/forums/241716-post69.html

The bottom line is that with a lens such as a 70-200 F2.8, adding a 2x teleconverter leads directly to a +1.5 stop over exposure.

this is due to the difference between metering at F2.8 and F5.6

In the posted graph, each 45 greyscale is rooughly 1 stop
09-16-2008, 02:49 PM   #12
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Try the Kenko 1.5x

QuoteOriginally posted by janosh Quote
I think a recent email from Pentax Forums said there was a tele extender forum somewhere.

Where is it?

Are any of the tele extenders for Pentax as nearly good as those for Canon (which are/were superb) ?

Are any of the current tele-extenders well made? (build quality was always in the past Vivitar/Sigma/Tamron's downfall, but Soligar did ok).
Just got the Kenko 1.5x and I am very pleased with the results. See the following thread...https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/37080-some-ken...-findings.html
FHPhotographer
09-16-2008, 02:56 PM   #13
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QuoteOriginally posted by Ben_Edict Quote
In my own experience the Sigma 2x APO is considerably worse, than the 1.4x APO - but I have seen photographs (Lowell?), which testify, that it can be of very high quality, too.
I don't know why this is, but one thing I have found is that due to the error in focal length and impact on SR, I find that perhaps people are not getting things as stable as they really need to be.

I shot both the posted photos in this thread at relitively high shutter speeds, since the 70-200 F2.8 plus the 2X is rather big fat and ugly.
09-17-2008, 03:49 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
...since the 70-200 F2.8 plus the 2X is rather big fat and ugly.
At least this combo is fat enough to stand up against the typical Cannons you meet at every event.

Ben
09-17-2008, 03:19 PM   #15
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QuoteOriginally posted by Ben_Edict Quote
At least this combo is fat enough to stand up against the typical Cannons you meet at every event.

Ben
Ben, the combo still leaves you with mm envy at an event.

This year I was in Rockford TX, and took a cruse out to see the whooping cranes, as Rockford is the wintering grounds. my sigma 70-200 F2.8 and 2x TC was the shortest, lightest , and also the slowest lens there.

The only thing I can say is that I was able probably to get more photos, because I could actually lift my lens
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