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02-24-2021, 01:10 PM   #1
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Shake reduction and teleconverter

I picked up a used 2x mc7 tamron-f af. It looks to be in good shape and works with my tamron 70-200 f/2.8. the focus is a bit slow but was affordable ($50 ish) so I can live with it.

As expected the camera (kp) is picking up the lens's focal length and aperture.

Is there anyway to tell it that I have a 2x converter attached so it adjust the shake reduction? I look in the manual and through the menus but could not find anything.

I assume I will also use it on my k3.

02-24-2021, 01:28 PM   #2
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QuoteOriginally posted by Sidney Porter Quote
I picked up a used 2x mc7 tamron-f af. It looks to be in good shape and works with my tamron 70-200 f/2.8. the focus is a bit slow but was affordable ($50 ish) so I can live with it.

As expected the camera (kp) is picking up the lens's focal length and aperture.

Is there anyway to tell it that I have a 2x converter attached so it adjust the shake reduction? I look in the manual and through the menus but could not find anything.

I assume I will also use it on my k3.
As far as I know only the hd da 1.4x adjusts the focal length and aperture to reflect the TC.
02-24-2021, 01:36 PM - 1 Like   #3
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Couldn't you cover the pins (aperture? lens data?) with a nonconductive material (dry paper / electrical insulating tape) to prompt the camera to ask for the focal length of the lens? Ideally only the pin(s) that transmit(s) focal length, so you'd still have an idea as to what focal length was used when viewing the EXIF later on?
02-24-2021, 02:00 PM   #4
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See Features and Operation of the KAF Mount | The K-Mount Page for which PIN it is :-)

02-24-2021, 02:02 PM   #5
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QuoteOriginally posted by ehrwien Quote
Couldn't you cover the pins (aperture? lens data?) with a nonconductive material (dry paper / electrical insulating tape) to prompt the camera to ask for the focal length of the lens? Ideally only the pin(s) that transmit(s) focal length, so you'd still have an idea as to what focal length was used when viewing the EXIF later on?
You would lose autofocus and aperture control via the body.
02-24-2021, 02:23 PM   #6
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Thanks for the suggestion. I don't care about the exif data but I don't want to lose aperture and autofocus.

If it can't be set with a menu item. I will live with the sr being slightly off. I figure I will often have a monopod and if shooting sports the shutter is fast enough that SR is less important
02-24-2021, 02:25 PM   #7
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QuoteOriginally posted by Sidney Porter Quote
As expected the camera (kp) is picking up the lens's focal length and aperture.
If you mean the recorded focal length is expected for that with the converter, then the SR will use the same value.


Steve
02-24-2021, 02:25 PM   #8
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QuoteOriginally posted by Sidney Porter Quote
Thanks for the suggestion
Be sure to do back to back images and try cropping 2x to see if the TC actually is better than just cropping.

02-24-2021, 02:29 PM - 1 Like   #9
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QuoteOriginally posted by UncleVanya Quote
Be sure to do back to back images and try cropping 2x to see if the TC actually is better than just cropping.
good idea. I will try that. Lacrosse season is starting so I will have opportunities to test it out

---------- Post added 02-24-21 at 04:33 PM ----------

QuoteOriginally posted by stevebrot Quote
If you mean the recorded focal length is expected for that with the converter, then the SR will use the same value.


Steve
I tested it at what should have been 400. It registered as 200. I didn't expect the converter to be smart enough to do anything more than pass the lens info. I was hopping that there was a menu item to tell the camera that a converter was on and multiple by 2 for the SR

---------- Post added 02-24-21 at 04:43 PM ----------

I also tested it with an old 70-300 4-5.6 promaster that must have been from my zx-10. I didn't expect auto focus to work with the 2 stop loss. It worked fine.I think I am giving credit to the kp rather than the lens or teleconverter
02-24-2021, 02:57 PM   #10
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That teleconverter just passes focal length information. On a tripod itís no big deal but the handheld SR will be off considerably if you donít cover the appropriate pin with tape. There are threads on PK about that I believe. The Pentax 1.7 AF adapter does communicate the appraise focal length if that is available. As previous folks have mentioned usually cropping beats the teleconverters for IQ.
02-24-2021, 03:09 PM   #11
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QuoteOriginally posted by Pentax Syntax Quote
That teleconverter just passes focal length information. On a tripod itís no big deal but the handheld SR will be off considerably if you donít cover the appropriate pin with tape. There are threads on PK about that I believe. The Pentax 1.7 AF adapter does communicate the appraise focal length if that is available. As previous folks have mentioned usually cropping beats the teleconverters for IQ.
The F 1.7 AFA? On my KP I had to input focal length but the aperture was accurately reflected with multiplier on a D FA 100 WR and the DA* 50-135. Using the HD DA 1.4x focal length and aperture were passed through correctly with multiplier. So the 1.7x would work best with non-Zoom where a fixed focal length input is sufficient.

I can try the k-3 or k100d but I expect it wonít change.
02-24-2021, 03:10 PM   #12
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QuoteOriginally posted by Pentax Syntax Quote
As previous folks have mentioned usually cropping beats the teleconverters for IQ.
That's definitely not the case with right lens+TC combo, especially if you can slightly stop down. I don't own the Tamron 70-200/2.8, but e.g. my Sigma 70-200/2.8 OS, when used on the Pentax 1.7x TC, delivers a lot more detail than a magnified crop when stopped down just 2/3 of a stop. Reports a weird aperture though ...
02-24-2021, 03:17 PM   #13
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QuoteOriginally posted by UncleVanya Quote
The F 1.7 AFA? On my KP I had to input focal length but the aperture was accurately reflected with multiplier on a D FA 100 WR and the DA* 50-135. Using the HD DA 1.4x focal length and aperture were passed through correctly with multiplier. So the 1.7x would work best with non-Zoom where a fixed focal length input is sufficient.

I can try the k-3 or k100d but I expect it wonít change.
Sorry for the confusion. Yes you must enter the teleconverted focal length but it does not just relay the lens focal length to the body. Yes I mostly use the 1.7 on prime lenses.

---------- Post added 02-24-21 at 05:21 PM ----------

QuoteOriginally posted by JensE Quote
That's definitely not the case with right lens+TC combo, especially if you can slightly stop down. I don't own the Tamron 70-200/2.8, but e.g. my Sigma 70-200/2.8 OS, when used on the Pentax 1.7x TC, delivers a lot more detail than a magnified crop when stopped down just 2/3 of a stop. Reports a weird aperture though ...
I agree. But I find the 2X tamron 7 element named by the OP to be a bit much. The Tamron 1.4 usually beats cropping. The Pentax 1.7 AF adapter almost always beats cropping.

---------- Post added 02-24-21 at 05:21 PM ----------

QuoteOriginally posted by JensE Quote
That's definitely not the case with right lens+TC combo, especially if you can slightly stop down. I don't own the Tamron 70-200/2.8, but e.g. my Sigma 70-200/2.8 OS, when used on the Pentax 1.7x TC, delivers a lot more detail than a magnified crop when stopped down just 2/3 of a stop. Reports a weird aperture though ...
I agree. But I find the 2X tamron 7 element named by the OP to be a bit much. The Tamron 1.4 usually beats cropping. The Pentax 1.7 AF adapter almost always beats cropping.
02-24-2021, 05:15 PM   #14
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Sadly, even when Pentax themselves did not make any teleconverters, they never provided an option for you to tell the camera had a lens with af teleconverter connected, and therefore correctly compensated for aperture and focal length,

The issue is more impacting than just shake reduction and Exif being wrong, it also impacts the P-TTL flash calculation, and the green biutton exposure accuracy, because even to this day, exposure is correctly set for between F4.0 and F5.6 because that is the kit lens aperture.

Faster lenses tend to over expose because the camera compensates for what it believes the aperture to be, via the contacts, as opposed to compensating for two stops with a 2x attached. There is a thread somewhere starting back in the K10D era, about exposure errors with manual aperture lenses, and with teleconverters
02-24-2021, 11:11 PM   #15
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QuoteOriginally posted by Sidney Porter Quote
Thanks for the suggestion. I don't care about the exif data but I don't want to lose aperture and autofocus.

If it can't be set with a menu item. I will live with the sr being slightly off. I figure I will often have a monopod and if shooting sports the shutter is fast enough that SR is less important
If your shutter speed is fast enough, just turn SR off. Especially for sports, using rear AF and tracking with AF-C in Manual. Simple.
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