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06-11-2007, 07:01 PM   #1
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Pentax converter with A lens?

Any non Pentax teleconverter used with Pentax A400 5.6 lens doesn't work properly. Have tried a Kenko 1.5, Phoenix 2X, and Tokina 2X (who makes Phoenix one). Camera can't adjust to proper wide open aperture. Will say f 2.8 etc for a lens with 5.6 max aperture. I wish!
Has anyone used a real Pentax converter with an A lens and had it work correctly? Do the Pentax converters even have the electrical contacts? Know they don't AF - could care less. Thinking about ordering a new Pentax 1.4 teleconverter if it will work properly. Help. Need more focal length.
thanks
barondla

11-25-2008, 03:13 PM   #2
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QuoteOriginally posted by barondla Quote
Any non Pentax teleconverter used with Pentax A400 5.6 lens doesn't work properly. Have tried a Kenko 1.5, Phoenix 2X, and Tokina 2X (who makes Phoenix one). Camera can't adjust to proper wide open aperture. Will say f 2.8 etc for a lens with 5.6 max aperture. I wish!
Has anyone used a real Pentax converter with an A lens and had it work correctly? Do the Pentax converters even have the electrical contacts? Know they don't AF - could care less. Thinking about ordering a new Pentax 1.4 teleconverter if it will work properly. Help. Need more focal length.
thanks
barondla
I was doing a google on the Pentax A400 5.6 lens and it's ability to be matched up with a tc. You've answer my question.
I would like to know if anyone has used the Pentax F 1.7 af tc with this lens and if so, how it worked.
11-25-2008, 03:48 PM   #3
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Since this was written I have found a teleconverter that works with the 400 5.6. It is a Promaster 1.7X af converter. Think I know why others don't work and how to tell if they will by looking at them. The non working converters loose an electrical contact from the front to the back of the converter! Count the number on lens end (front) and camera end (back). If they don't mach they won't work properly with F5.6 lenses!
My Promaster looks just like the Kenko 1.4 (slightly longer). Obvious they came from same factory. Why one is missing the extra pin on he back - who knows!
Have never used the Pentax converters but bet they work.

thanks
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11-25-2008, 04:23 PM   #4
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QuoteOriginally posted by barondla Quote
Any non Pentax teleconverter used with Pentax A400 5.6 lens doesn't work properly. Have tried a Kenko 1.5, Phoenix 2X, and Tokina 2X (who makes Phoenix one). Camera can't adjust to proper wide open aperture. Will say f 2.8 etc for a lens with 5.6 max aperture. I wish!
Has anyone used a real Pentax converter with an A lens and had it work correctly?
Must be something special about that lens, or something *wrong* it or your TC. Because my Kenko 1.5 works just fine with my A50/1.7. That is, it dials down to a reading of 1.7 just as you'd expect, even though we all know the results are really a stop slower.

11-25-2008, 04:48 PM   #5
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QuoteOriginally posted by LaRee Quote
I was doing a google on the Pentax A400 5.6 lens and it's ability to be matched up with a tc. You've answer my question.
I would like to know if anyone has used the Pentax F 1.7 af tc with this lens and if so, how it worked.
Your wasting yoour time with the 1.7X AF TC on a lens slower than F4. I have heard some people claim it works on F4.5 lenses, like the 500 F4.5 but I am not so sure.

I use it with my 300 F4 all the time, but that is it. Note, it was origonally released to work only with lenses faster than F2.8

I have used this with F4 lenses on my PZ-1, *istD and K10D. Good thing my camera's can't read
11-25-2008, 05:40 PM   #6
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Thank you for the responses guys. I new about most tc wanting f2.8 or faster lenses but I wanted to see if anyone had used one with this lens. I wonder how difficult it is to find the Promaster 1.7 af tc?
11-25-2008, 11:29 PM   #7
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QuoteOriginally posted by Lowell Goudge Quote
Your wasting yoour time with the 1.7X AF TC on a lens slower than F4. I have heard some people claim it works on F4.5 lenses, like the 500 F4.5 but I am not so sure.
Hi Lowell,

I use my F1.7x AFA with my FA*300/4.5 virtually every day with my K20, K10, and DS. I think that top tier wide open optical performance (contrast and sharpness) makes the difference. I haven't found any slower lenses that it will AF with, even in the middle of the summer at noon on a cloudless day, so I'd say that f 4.5 in a very good lens is probably the practical limit.

Not really practical, but I did get it to work with my Sigma EX300/2.8 APO, a Sigma 1.4x APO,Tamron F 1.4x AF TC (which would give a max aperture of f5.6 together), and the AFA for a total of almost 1000mm. The IQ wasn't very good, but was actually acceptable for a smallish print. I wouldn't recommend this combo, but it did AF, and the lighting was far from optimal. I was very surprised because I'd previously tried it with a Tokina 150-500/5.6 AT-X SD (a reasonably sharp beast), but could never get it to lock, even in very bright sunlight with a very contrasty subject.

Scott
11-25-2008, 11:47 PM   #8
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Thank you for your input Scott.
btw, how the heck are you?

11-26-2008, 06:26 AM   #9
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Marc, nothing wrong with the A400 5.6. The problem is the little electrical contact that Pentax uses to tell camera max ap is missing on many teleconverters ( excluding their own). The same converters don't work on my friends Pentax 250-600 5.6 either (wish I owned that one). Any lens with 5.6 max ap are out of luck. My Kenko 1.5 works on all my other lenses fine. Don't really care about af.

LaRee, no idea how hard it would be to find Promaster 1.7. Bought mine in camera store used for ~$60. Would never get rid of it now.
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11-26-2008, 06:39 AM   #10
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QuoteOriginally posted by LaRee Quote
Thank you for the responses guys. I new about most tc wanting f2.8 or faster lenses but I wanted to see if anyone had used one with this lens. I wonder how difficult it is to find the Promaster 1.7 af tc?
Here ya go LaRee

1.7X AF Teleconverter for Pentax Auto Focus Lenses NEW - eBay (item 120325306263 end time Nov-27-08 06:46:57 PST)

I think a couple people have done a short review on these teleconverters. I've thought about getting one and still may.
When I first got my Sigma 100-300 I went to Yellowstone Park over Memorial weekend. I stopped in Jackson Hole at a camera shop looking for a teleconverter and the Promaster was the only one they had for Pentax. At that time I never heard of it so I passed it up. I wish I hadn't now because I really could have used it there.

Last edited by OrenMc; 11-26-2008 at 06:50 AM.
11-26-2008, 07:08 PM   #11
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QuoteOriginally posted by barondla Quote
Marc, nothing wrong with the A400 5.6. The problem is the little electrical contact that Pentax uses to tell camera max ap is missing on many teleconverters ( excluding their own).
OK, but then how come that same (?) TC works with my A50/1.7 (and all my other lenses, too), communicating max aperture just fine? It seems to me that TC *does* have this contact. Or perhaps there are two different versions of the Kenko 1.5 TC? That much I actually don't doubt for a minute - I keep hearing references to 5 versus 7 element, so having pz/sdm contacts or not, etc.
11-27-2008, 12:02 AM   #12
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There is info at this page about the lens contacts: Pentax Lens Modifications for Matrix Metering - Mark Roberts Photography.

It looks like if you insulate the camera contact from the spot where the pin is missing on the TC, your A 400 will be able to transmit min/max aperture.

Last edited by clm; 11-27-2008 at 09:06 AM. Reason: added "able to"
11-27-2008, 12:09 AM   #13
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[QUOTE=OrenMc;402987]Here ya go LaRee

1.7X AF Teleconverter for Pentax Auto Focus Lenses NEW - eBay (item 120325306263 end time Nov-27-08 06:46:57 PST)

QUOTE]

That one also has only 6 pins at the camera side.
11-27-2008, 12:26 AM   #14
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QuoteOriginally posted by clm Quote
There is info at this page about the lens contacts: Pentax Lens Modifications for Matrix Metering - Mark Roberts Photography.
Wow, that's interesting.

But the page starts with a big caveat that this doesn't apply to digital SLRs? Does it nevertheless?
11-27-2008, 01:29 AM   #15
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QuoteOriginally posted by clm Quote

It looks like if you insulate the camera contact from the spot where the pin is missing on the TC, your A 400 will be transmit min/max aperture.
Yes, that's what I've done with Kenko 1.5 TC and it works fine with A 400/5.6. Small piece of tape is all you need
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