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01-02-2016, 08:48 PM   #1
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Pentax 150-450mm with/without 1.4x rear converter

Hello All,
I have been a bit suspicious that shots with my HD PENTAX-D FA 150-450mm F4.5-5.6ED DC AW with HD PENTAX-DA AF Rear Converter 1.4x AW were consistently less sharp that when not using the 1.4x TC, so I did a little test to see if I was right.
All shot with K-3 II, at about 10m, shake reduction ON, handheld.
The first two are with TC, second two are without TC.
Is this an expected result?
Is it possible that the combination needs AF adjustment?

Cheers,
Terry

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01-02-2016, 08:55 PM   #2
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Interesting. Subscribing to see the outcome. It would be interesting to do the same test from a tripod to eliminate the SR variable.
01-02-2016, 09:02 PM   #3
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QuoteOriginally posted by colonel00 Quote
Interesting. Subscribing to see the outcome. It would be interesting to do the same test from a tripod to eliminate the SR variable.
I made two shots for each case to see if there was any consistency, and to my eye both shots with TC are noticeably less-sharp than both without TC, but it is probably a good idea to shoot another set from tripod without SR.
I'm off to do it now!

Cheers,
Terry
01-02-2016, 09:05 PM   #4
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Yeah, the one thing I notice is there seems to be a noticeable difference between the first two shots with the TC. Just made me wonder if there was some other variable or a combination of things going on.

01-02-2016, 09:31 PM   #5
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My suggestion: Try shooting some shots (both with and without TC) focused using live view (CDAF) and compare to those focused not using live view (i.e. PDAF). The results should provide added insight regarding what the issues and solutions might be.
01-02-2016, 09:32 PM   #6
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QuoteOriginally posted by colonel00 Quote
Yeah, the one thing I notice is there seems to be a noticeable difference between the first two shots with the TC. Just made me wonder if there was some other variable or a combination of things going on.
Not sure what that would be, other than me wobbling and SR not managing.

Cheers,
Terry
01-02-2016, 09:34 PM   #7
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QuoteOriginally posted by tduell Quote
Not sure what that would be, other than me wobbling and SR not managing.

Cheers,
Terry
I don't know either but they look quite different. even the framing of the envelope is different like you were closer or cropped it differently? Just pointing out observations which could lead to puzzling results. As darylk mentions, test with different focusing methods as well.
01-02-2016, 09:37 PM   #8
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The testing over in the 300mm lens club thread contradicted your results. However, there are so many variables that it might be difficult to make any offhand determination?

Regards!

01-02-2016, 09:37 PM   #9
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The first photo looks like it's mis-focused, and the second might be as well. I'd definitely re-shoot the tests on a tripod using live view to focus.

A bit of softness is to be expected wide-open at 450mm, but not as severe as in these images.

Adam
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01-02-2016, 09:39 PM   #10
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OK, just shot the series again, this time using tripod, live-view, and cable release.
To my eye these results make it rather undecided, as I reckon none are quite as sharp as the two handheld without TC, but I reckon it may be my old eyes.
I would add that I don't think my tripod is without a bit of vibration either. I really need a decent way of taking that out of the equation too. I have tried a suspended bag of bricks in the past, but if can't stop that from moving it juts adds to the problem.

Anyway, here are the tripod shots, as before first two with TC, last two without.
Cheers,
Terry

---------- Post added 01-02-16 at 09:46 PM ----------

QuoteOriginally posted by colonel00 Quote
I don't know either but they look quite different. even the framing of the envelope is different like you were closer or cropped it differently? Just pointing out observations which could lead to puzzling results. As darylk mentions, test with different focusing methods as well.
All the first set shot from approx the same place (within 500mm) but there wasn't a standard crop used for all, just cropped by eye. I was only looking for sharpness differences, so minor crop differences are not (in my view) important.

Cheers,
Terry
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01-02-2016, 09:47 PM   #11
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QuoteOriginally posted by tduell Quote
Hello All,
I have been a bit suspicious that shots with my HD PENTAX-D FA 150-450mm F4.5-5.6ED DC AW with HD PENTAX-DA AF Rear Converter 1.4x AW were consistently less sharp that when not using the 1.4x TC, so I did a little test to see if I was right.
All shot with K-3 II, at about 10m, shake reduction ON, handheld.
The first two are with TC, second two are without TC.
Is this an expected result?
exif says 1/500th, 630.0mm (35mm equivalent: 945mm), and you said hand-held? you are pushing it too hard for a test procedure, so the result is as expected.

the object of testing is to first eliminate variables, so as mentioned earlier, you should be on a tripod, sr off, or at least a much faster shutter... focus manually with live view, like daryl said, to establish a baseline showing the best possible pq... then start checking it with af.

o.k, i see that you just posted the second round... looks like a mis-focus on the third pic? but the loss of contrast on the first two shots makes sense, because of the tc, even tho they are exposed differently.
01-02-2016, 09:58 PM   #12
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QuoteOriginally posted by osv Quote
exif says 1/500th, 630.0mm (35mm equivalent: 945mm), and you said hand-held? you are pushing it too hard for a test procedure, so the result is as expected.
For the first set the SR was ON, so are you saying that it couldn't be expected to cope?

QuoteQuote:
the object of testing is to first eliminate variables, so as mentioned earlier, you should be on a tripod, sr off, or at least a much faster shutter... focus manually with live view, like daryl said, to establish a baseline showing the best possible pq... then start checking it with af.

o.k, i see that you just posted the second round... looks like a mis-focus on the third pic? but the loss of contrast on the first two shots makes sense, because of the tc, even tho they are exposed differently.
All have exactly the same exposure settings. The light has been varying a bit.

Cheers,
Terry

---------- Post added 01-02-16 at 10:11 PM ----------

QuoteOriginally posted by osv Quote
the object of testing is to first eliminate variables, so as mentioned earlier, you should be on a tripod, sr off
I agree in principal with that, but I shoot handheld with SR on, so my first aim was to see if I can detect any differences when shooting this way using a standard target. Once I could see what that tells me, and what others see in those result, I can then decide what next.

Thanks for your thoughts on this.

Cheers,
Terry
01-03-2016, 06:55 AM   #13
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I did a series of IQ tests of several long lenses with and without the HD1.4X. See the long lens thread* starting on page 1259.

*The 300mm plus long lens club discuss your long lenses"
01-03-2016, 09:47 AM   #14
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QuoteOriginally posted by tduell Quote
For the first set the SR was ON, so are you saying that it couldn't be expected to cope?
in general, ibis/ois can be a mixed bag when used on a tripod... even in the best case, it introduces another variable.

i'd first test without it, establish a pq baseline, using a fast shutter and higher iso, then test with it.

QuoteOriginally posted by tduell Quote
All have exactly the same exposure settings. The light has been varying a bit.
the tc attenuates light, but those pics in the second test are brighter, i see your point there.

i thought that the 2nd test does indicate decent sharpness with the tc??

QuoteOriginally posted by tduell Quote
I agree in principal with that, but I shoot handheld with SR on, so my first aim was to see if I can detect any differences when shooting this way using a standard target. Once I could see what that tells me, and what others see in those result, I can then decide what next.
gotta test for that as well, in general i do those things last, after establishing a pq baseline that shows what the combo can do under the best circumstances.
01-03-2016, 10:11 AM   #15
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You're shooting with the lens stopped down by one stop and the lens + the TC wide open?!!!

Not a fair test anyway, if we accept that hand holding the lens with the TC on is not causing any IQ degradation due to shaking or misfocusing...
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