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10-25-2018, 06:18 AM   #1
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Thoughts about using Pentax 1.4x HD PENTAX-DA AF Rear Converter AW

Hello,

I was wondering if anyone has any experience using
Pentax 1.4x HD PENTAX-DA AF Rear Converter AW
with
Pentax HD PENTAX-DA 55-300mm f/4.5-6.3 ED PLM WR RE Lens

Will you recommend it? I like the extra reach and my budget does not allow for the HD Pentax-D FA 150-450mm F4.5-5.6 (APS-C).

What are your thoughts about Pentax 1.4x HD PENTAX-DA AF Rear Converter AW?

Thank you!

10-25-2018, 06:42 AM   #2
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See dark64 post on this thread, third post top to bottom.
10-25-2018, 06:53 AM - 3 Likes   #3
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Just as a general rule, shooting with a lens that is ƒ8 or above presents it's own set of problems. It's not really about the TC, it's about the ƒ-stop you have when you put one on an already slow lens.

My recommendation has always been use a TC on star quality , fast glass. Preferably 2.8 or possibly ƒ4. That would be for optimum usage. But if in a tight budget you might be able to squeeze some functionality out of a DA 55-300 PLM and the Pentax 1.4/

The Pentax comments in the lens data base are completely ignorable, largely written by people who don't understand what a TC does, or what it should be used for.

Let me deal with a few of the issues.

The Pentax 1.4 TC like all TCs is designed to augment good long lenses.
With a soft lens a TC magnifies the softness.
With a sharp lens the TC magnifies the sharpness.
If the lens produces aberrations, the TC will magnify the aberrations.

That is a function of all TCs.

The lenses the Pentax TC works best on would be the DA*300 ƒ4, the DA* 60-250, ƒ4, the DA*200 ƒ2.8, and to a lesser extent the DA 150-450 and DA 560. It also works well on the Sigma 500 4.5, and I'm guessing on the DFA 70-200 on APS-c. I also use mine with my Tamorn 300 2.8. I can vouch for these lenses absolutely. All these lenses also work well with the F 1.7x AF adapter, so they are all capable of benefitting from even more magnification, the one lens I haven't personally tested being the DA*300, but if anything, it's better than my DA*60-250 which benefits from both.

So in short, TCs aren't for every lens and every focal length. All TCs do poorly on shorter focal length lenses.
The advantage to the Pentax TCs, accurate reporting of focal length and lens info, meaning the shake reduction system will perform as it was designed to. I can use the Pentax 1.4 hand held, with my Tamron 2x and many other TCs they don't correctly record the focal length and the SR causes softness, rendering it completely ineffective. But on a tripod with a 2 second delay, you can get good results with 3rd party TCs.

But for the OP, the biggest reason for getting the Pentax TC is he will get some acceptable results now, but if he buys one of the listed lenses in the future he will get excellent images.

But not only telephoto is enhanced by the TC. We use TCs on our DFA 100 macro and Tamron 90 macro to push the enlargement factor above the 1:1 they were designed for. It can be used with he Sigma 70, Tarmon 90 or DFA 100 macro with with positive effect as those lenses are plenty sharp enough to magnify them with good effect. The TC takes any of those lenses from 1:1 to 1.4:1 magnification.The only weak part of the Pentax TC is the lens you put it on.

Conclusion
The TC increases magnification by 40% for a 3% loss of resolution, for a possible net gain of 37%. How much of that you get depends on whether or not your lens has an extra 40% resolution above what your sensor requires for a sharp image. On lower cost lenses like the 55-300 PLM I've seen mixed results. with a lens like that which is quite good out of the box with no TC, sample variation plays much bigger part in how effective the TC will be than on a lens like a DA* where even if your copy isn't the sharpest one of it's type, it will certainly benefit, because of their higher baseline resolution standard.

Bottom line, TCs are for lenses 50mm-70mm or over with resolution to burn, and don't work well with apertures wider than ƒ2. A 1.4 TC on a 2.8 or ƒ4 telephoto is a wonderfull thing. For apertures over ƒ4 they are less wonderful but still often useable with good results. Keep that in mind and you won't be disappointed.

Last edited by normhead; 10-25-2018 at 08:04 AM.
10-25-2018, 07:01 AM - 1 Like   #4
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I don't have the PLM, but my experience with the older SMC 55-300 and the TC is not very good. I think I get marginally better quality if I just crop instead using the K-3. It could be that it works better on e.g. a K-5 with its lower resolution. Oh, and this combo does require a lot of light for the autofocus to work well.

10-25-2018, 07:08 AM   #5
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I've tried several 1.4x tc's with my dal 55-300 ( a lens I don't use very often because it has a fault: focus mechanics are stiff. if my pentax has a fully charged battery it still focuses usually but I worry about stressing the system). I can say that:
1.. All autofocused in good light. It gets much more iffy as soon as the light drops.
2. All maintained decent IQ (see this discussion thread on 1.4x tc's here). Whether cropping more would have done as well is however the 64,000 dollar question.


Personally I wouldn't pay ~$500 for the premium pentax tc to use on a DA55-300. It's a moot point whether the increased reach won't be offset by lower IQ from slower shutter speeds and increased effect of shake and vibration, and shallower depth of field (this can be subject dependent - eg birds with fine detail i would say its not so helpful. Ships/airplanes howeverwith tripod mounted set up tc's can help). I would actually like to be able to compare the pentax to eg my sigma apo to see if there is some iq justification for the price.

There are a number of discussion threads on super telephoto options. For $500 you might with a bit of luck, get my lens the adaptall 300mm f2.8, albeit its MF of course. Now that works well with a 1,4x.
10-25-2018, 07:08 AM   #6
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QuoteOriginally posted by NickTent Quote
Thoughts about using Pentax 1.4x HD PENTAX-DA AF Rear Converter AW
Works very well. 1st photo full ext 420mm, 2nd photo about 1/4 ext. 125mm

Last edited by honey bo bo; 12-04-2018 at 03:34 PM.
10-25-2018, 08:07 AM   #7
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I look at honey bo bo's images, and I look at some of the others I've seen including my own and ask "Do you feel lucky."
Honey has always been happy with her results and I suspect her copy of the 55-300 is at the top end of the sample variation spectrum, so the big question becomes is your copy like hers, or like one of the ones where the people weren't so happy. Don't ever sell that lens honey bo bo. If you do, sell it to me.

10-26-2018, 01:49 AM - 1 Like   #8
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Nick, I've tried the PLM with my Kenko 1.5x pz TC. The AF works, but nothing in the samples made me think the results were better than cropping (on the K-3 anyway). The PLM is a very good lens, but its resolution is not stellar at 300mm (e.g. a small bird at more than about 10 metres). I'd suggest you save the $500 you would spend on the Pentax TC and put it towards getting a premium telephoto lens. The F*/FA*300mm f4.5 at around $700 or so would be a better use of the money IMO. Those lenses will work with a range of third party TCs that are a lot cheaper - giving a great value 420mm f6.3 combination.

Last edited by Des; 10-26-2018 at 12:47 PM.
10-26-2018, 02:20 AM - 2 Likes   #9
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I have the combo and sometimes get great results towards infinity, sometimes not. It's not my main use and can't tell enough where my technique or combo fail.
The combo means I have reach biking around because I won't have a big heavy lens with me.
Where I use it most is at closer distance. With out the tc I can frame a butterfly at 2 paces and with the tc I can from close to 3 paces.
The f9.5 at the long end isn't your friend.
10-26-2018, 03:50 AM   #10
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Original Poster
Hello Everyone,

Thank you very much for the replies, suggestions and advice!!

While some people had good results with the combination of lens and TC , I think I will save the money to buy a better lens with long reach .

Thanks again,

Nick
10-26-2018, 03:59 AM   #11
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QuoteOriginally posted by NickTent Quote
Hello Everyone,

Thank you very much for the replies, suggestions and advice!!

While some people had good results with the combination of lens and TC , I think I will save the money to buy a better lens with long reach .

Thanks again,

Nick
When you get the better lens you can use the TC with that as well and get even more reach

10-26-2018, 05:42 AM - 1 Like   #12
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QuoteOriginally posted by Des Quote
Nick, I've tried the PLM with my Kenko 1.5x pz TC. The AF works, but nothing in the samples made me think the results were better than cropping (on the K-3 anyway). The PLM is a very good lens, but its resolution is not stellar at 300mm (e.g. a small bird at more than about 10 metres). I'd suggest you save the $500 you would spend on the Pentax TC and put it towards getting a premium telephoto lens. The F*/FA*300mm f4.5 at around $700 or so would be a better use of the money IMO. Those lenses with work with a range of third party TCs that are a lot cheaper - giving a great value 420mm f6.3 combination.
This has been my experience as well when I tried the 1.4 TC with my 55-300 PLM. I found I could get just as good, if not better results by just cropping images from the lens without the TC. Also, I do not zoom my PLM all the way out to 300mm. I stop at about 270 to 280mm where the lens is still f5.6
Its a different and better situation when I use the TC with my primes: DFA 100 macro WR, DA*200 and DA*300 where I do get the extra reach and maintain the lenses original sharpness, at least to my eyes. I use my TC mostly with the DA* 300 to get a 420mm f5.6 prime lens.
I never tried the TC with any of my shorter focal length lenses since I bought it exclusively for extended telephoto reach.
10-26-2018, 08:05 AM   #13
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QuoteOriginally posted by jddwoods Quote
I use my TC mostly with the DA* 300 to get a 420mm f5.6 prime lens.
Tha combination seems to be a wonderful thing. Probably what it was designed for.
10-26-2018, 01:10 PM - 2 Likes   #14
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QuoteOriginally posted by jddwoods Quote
ts a different and better situation when I use the TC with my primes: DFA 100 macro WR, DA*200 and DA*300 where I do get the extra reach and maintain the lenses original sharpness, at least to my eyes. I use my TC mostly with the DA* 300 to get a 420mm f5.6 prime lens.
QuoteOriginally posted by normhead Quote
Tha combination seems to be a wonderful thing. Probably what it was designed for.
Still a great option. Excellent image quality, WR, much lighter weight than the long zooms. If only the TC were cheaper.

QuoteOriginally posted by NickTent Quote
I think I will save the money to buy a better lens with long reach .
Wise move IMO. In the meantime, you can have a lot of fun with the DA 55-300 PLM. I've got that lens and the K-S2 and they are a very good, lightweight, portable, compact, WR combination. I agree with @jddwoods that it's best to back off a little from 300mm if you can.

K-S2 + D 55-300 PLM
















10-26-2018, 01:33 PM   #15
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QuoteOriginally posted by normhead Quote
Honey has always been happy with her results and I suspect her copy of the 55-300 is at the top end of the sample variation spectrum, so the big question becomes is your copy like hers, or like one of the ones where the people weren't so happy. Don't ever sell that lens honey bo bo. If you do, sell it to me.
I don't quite know how to break it to you Norm, but Honey's handle and avatar point in a different direction to "her" profile.

QuoteOriginally posted by honey bo bo Quote
Works very well. 1st photo full ext 420mm, 2nd photo about 1/4 ext. 125mm
Cheers to you Bruce!
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