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12-18-2007, 01:18 PM   #1
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teleconverter comments, anyone?

Can you folks tell me abit about the quality and use of your teleconverters, if you have them? a quick Amazon search reveals the followings (USD):
1. Kenko DG, 2X, $69
2. Sigma APO EX, 1.4X, $189
3. Sigma APO EX, 2X, $189
4. Pentax SMC-A, 1.4X, $379
Of course, some of you have other teleconverter in the inventory. so the questions are:
a. are any of these retains automatic apperture or auto focusing?
b. is the loss of IQ significant (pixel peeping bad)?
well...i've been saving for a DA50-135 (or, a 100mm macro) as i heard they are outstanding portrait lens. The problem is a lack of long range end. a 1.4x would bring it to 189mm, quite adequate w/o too much loss of light, while retaining the same close-focus ability (not that the 50-135 is famous close-focusing or anything like that, it's at a lousy 1m, the 100mm macro in the other hand...)
Of course, if you think such combination will result in a lousy IQ... I'd just rethink my LBA otherwise.

12-18-2007, 01:27 PM   #2
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I have both sigma's but be careful with them, as the element is very far forward and may interfere with many of your lenses rear elements, they are somewhat sigma specific. They are specifically for my 70-200f2.8 to give extra reach, and work very well, especcially the 1.4x.

I also have Vivitar MC 2x and 3x TCs from when I was young and foolish and thought focal length was free. They have not been used in years.

In addition to all of that, I have a KA mount Takumar 2x TC which seems quite good, AND the famous Pentax Autofocusing 1.7x TC which is almost perminantly attached to my 300mmF4

Edit note

With what I have plus a few comments the list is as follows

1. Kenko DG, 2X,
2. Sigma APO EX, 1.4X, Full frame but not digitally optimized
2a, Sigma APO EX-DG, 1.4X, Full frame digitally optimized
2b, Sigma APO EX- DC, 1.4X, ASP-C sensor digitally optimized
3. Sigma APO EX, 2X, Full frame but not digitally optimized
3a, Sigma APO EX-DG, 2X, Full frame digitally optimized
3b, Sigma APO EX- DC, 2X, ASP-C sensor digitally optimized
4. Pentax SMC-A, 1.4X,
5. Takumar -A, 2x
6. Pentax SMC-F, 1.7x, AF adaptor
7 Vivitar MC-22, 2x
8. Vivitar -22, 3x

Last edited by Lowell Goudge; 12-18-2007 at 01:51 PM.
12-19-2007, 06:18 AM   #3
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I've got a Sigma 1.4x EX DG teleconverter to match my 70-200 f2.8. It doesn't really affect image quality, but hand held, AF speed is a lot lower.
12-19-2007, 07:50 AM   #4
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This is another case of a need for a non pentax database, with some technical details and reviews.

EDIT Note

Out of curiosity, I looked at the table on the datasheet for my 2 sigma TCs.

For Pentax,

the Origonal 1.4x and 2x EX TCs are only useable on the sigma 70-200 f2.8, the 300mm F4 and 400mm F5.6 plus Pentax FA 200 F2.8, FA 300 F2.8, FA 600 F4
The newer 1.4x and 2x EX - DG TCs are useable on Sigma 180 mm F3.5 Macro, 300 MM f2.8, 70-200 f2.8, the 300mm F4 and 400mm F5.6, 500 mm F4.5, 800mm f5.6 and the BIGMA.

I would imagine that the EX-DG Teleconverters are useable ont he origonal pentax lenses listed, and visa versa, but it is interesting that they specifically exclude other Sigma lenses also.


Last edited by Lowell Goudge; 12-19-2007 at 08:09 AM. Reason: new data added
12-19-2007, 09:53 AM   #5
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QuoteOriginally posted by SupremeMoFo Quote
I've got a Sigma 1.4x EX DG teleconverter to match my 70-200 f2.8. It doesn't really affect image quality, but hand held, AF speed is a lot lower.
Could you check to see if the TC 1.4 works with your DA 16-45 at all? I know it's a silly combination, but that will tell if the TC is compatible with shorter zoom DA design. Mechanical inteference (jamming of the glasses, etc) could be a concern.

thanks
12-19-2007, 11:59 AM   #6
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Not directly related to the OPs question but I would like to add one thing.
If Pentax does not release a 1.7X and 2X TC with SDM capability for and with DA*200 and 300 lenses, I would say them just stupid.
12-19-2007, 03:26 PM   #7
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I just went outside and shot these 2 photo's with my Tamron 18-250. The first was with the Tamron 1.4X Pz-AF MC4 Teleconverter. See if you see much difference in IQ.


By fl_gulfer, shot with PENTAX K100D at 2007-12-19


By fl_gulfer, shot with PENTAX K100D at 2007-12-19
12-19-2007, 03:38 PM   #8
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The top image looks a bit more contrasty, in the sign and the yellow/green leaves. I like the top one better.

12-19-2007, 04:10 PM   #9
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Tomorrow I'll set up my tripod and try the converter with a few different lenses and see if there is much of a difference.. any suggestions on what to take photo's of? The wife is out of the question and I don't know anyone else to take shots of. So people shots are out of the question. I have this one and payed $89.00 but the price has went up since then.

Tamron | 1.4x Teleconverter for Pentax AF | AF14P700 | B&H Photo
12-19-2007, 04:33 PM   #10
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QuoteOriginally posted by Fl_Gulfer Quote
Tomorrow I'll set up my tripod and try the converter with a few different lenses and see if there is much of a difference.. any suggestions on what to take photo's of? The wife is out of the question and I don't know anyone else to take shots of. So people shots are out of the question. I have this one and payed $89.00 but the price has went up since then.

Tamron | 1.4x Teleconverter for Pentax AF | AF14P700 | B&H Photo
Here is my thought on test subject: since the bokeh and focus will (hopefully) be all the same, the two important IQ are contrast and resolution. A brick wall and something with contrast details (bushy plants or low contrast subject) would make excellent test subject. If you can post full-crop snapshot at center& edge, that would tell a heck of a story.
12-21-2007, 12:58 PM   #11
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This is without converter center crop:


This is with Converter center crop


Without bottom right, crop


With Bottom Right


I doubt if these are good enough but I tryed.
12-21-2007, 01:02 PM   #12
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Center crop without


Center Crop With converter


Bottom Right Without


Bottom Right With
12-21-2007, 01:48 PM   #13
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it would be interesting to see how much the addition of a TC to a lens contributes to purple fringing?
12-21-2007, 04:46 PM   #14
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QuoteOriginally posted by Lowell Goudge Quote
it would be interesting to see how much the addition of a TC to a lens contributes to purple fringing?
The aberrations of the prime lens will be increased in size by the multiplication factor of the TC. If your purple fringe is 10 pixels on a lens, with a 1.4x TC it will increase to 14 pixels, 20 pixels with the 2x.

In simplistic terms, whatever comes out of the back end of the lens will be proportionately larger. In addition, if the converter adds some fringing, it will be worse.

I am not sure that I will be using my A 1.4x-S any more, now that my 400 is equivalent to 600, which is what I used the 1.4x for.
12-21-2007, 10:01 PM   #15
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Without Center


With Center


Without Right


With Right
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