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02-01-2018, 11:34 PM   #1
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Which Rear Converter for SMC K 400mm 1:5.6? 1.4x-S or 1.4x-L?

It's not clear in the Lens info on this site. Rear converter 1.4x-S is supposedly only for lenses 300mm and less, but the 1.4x-L does not specify that it will definitely work with the SMC K 400mm 1:5.6. I'd probably prefer to use the 1.4x-L, but not if it does not physically fit of course. Anyone tried it?

02-02-2018, 12:02 AM   #2
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QuoteOriginally posted by vyoufinder Quote
It's not clear in the Lens info on this site. Rear converter 1.4x-S is supposedly only for lenses 300mm and less, but the 1.4x-L does not specify that it will definitely work with the SMC K 400mm 1:5.6. I'd probably prefer to use the 1.4x-L, but not if it does not physically fit of course. Anyone tried it?
Use the S, as the L won't fit inside the barrel.

If you're shooting on crop, the DA 1.4x would also work wonders.

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02-02-2018, 01:35 AM   #3
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QuoteOriginally posted by Adam Quote
Use the S, as the L won't fit inside the barrel.

If you're shooting on crop, the DA 1.4x would also work wonders.
Thanks. I won't look for a 1.4x-L then. Saved me trouble of finding out the hard way. Not shooting on cropped sensors. It seems that the SMC K 400 5.6 has the same barrel size as the M series? I think that because I see the M series on the list not capable to work with the 1.4x-S, but not the K. The reason I ask is because I also do not see the K series listed on the supported list of lenses for the 2x-l, yet I do see the M series 400 5.6 listed there.. Am I safe to assume that I could use the 2x-L on the SMC K 400 5.6? Maybe I look at one of those.
02-02-2018, 04:42 AM   #4
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The clearance requirements of the 1.4XL and 2XL converters are exactly the same. If one will not fit, neither will the other. I had both (the 1.4XL has now gone to another Pentaxian) and they will fit (just barely) and function well on a Tamron 400mm f4.

02-02-2018, 07:39 AM   #5
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The 1.7x F may also be an interesting option.
02-02-2018, 08:07 AM   #6
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QuoteOriginally posted by UncleVanya Quote
The 1.7x F may also be an interesting option.
I works poorly on my A-400 5.6. I'm not sure why. I don't know if it's the A-400 just sin't sharp enough for that amount of magnification. or if the resulting 9.3 minimum aperture doesn't provide enough light for accurate focusing.
02-02-2018, 11:03 AM   #7
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QuoteOriginally posted by normhead Quote
I works poorly on my A-400 ƒ5.6. I'm not sure why. I don't know if it's the A-400 just sin't sharp enough for that amount of magnification. or if the resulting ƒ9.3 minimum aperture doesn't provide enough light for accurate focusing.
f/5.6 is likely pushing it with that adapter. I have used it in some stacked TC configurations where the f/stop is that high but in that case I was shooting the moon at infinity so it was relatively low complexity and a very bright subject.

02-02-2018, 01:16 PM   #8
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QuoteOriginally posted by vyoufinder Quote
I think that because I see the M series on the list not capable to work with the 1.4x-S, but not the K.
I think any lens is technically compatible with the 1.4x S with only a handful of exceptions (i.e. lenses with a protruding element). The image quality just isn't as good as the 1.4x L, but since that TC can only be fitted on a handful of lenses, the point is moot.

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03-15-2020, 05:05 AM   #9
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Does anyone here (if you're still monitoring this thread!) know whether the 1.4X-L will work well or at all with the Sigma 400mm f/5.6 AF lens, which is reviewed here: Sigma / Carl Zeiss Jena (AF and MF) 400mm F5.6 IF MC multicoated Lens Reviews - Sigma Lenses - Pentax Lens Review Database

I'm wondering if the protruding lens on the converter will fit inside the Sigma lens' back, because there is room inside the back of the lens for such a portrusion. Just wondering it it's big enough for the converter.

Also wondering if the quality of photos would likely be good or not using the 1.4X-L / Sigma lens combination....

Thanks,

Mike
03-15-2020, 06:25 AM   #10
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QuoteOriginally posted by vyoufinder Quote
It's not clear in the Lens info on this site. Rear converter 1.4x-S is supposedly only for lenses 300mm and less, but the 1.4x-L does not specify that it will definitely work with the SMC K 400mm 1:5.6. I'd probably prefer to use the 1.4x-L, but not if it does not physically fit of course. Anyone tried it?
The lists of lenses that are supported and NOT supported are on the Review pages for the Rear Converters themselves, found at the bottom of the Lenses Compatible with all Pentax Digital SLR’s table.

The A 400/5.6 is specifically listed as supported for the A 1.4x-L Rear Converter.

Interestingly to me - “All other lenses above 300mm“ are specifically listed as NOT supported for the A 1.4x-S Rear Converter, but the A 1.4x-S fits my K400/5.6 andt the 1.4x-L doesn’t. The K4400/5.6 is not documented on either list.

See links below.

Supported lenses for A 1.4x-L Rear Converter from the Review page for the TC

Not Supported lenses for the A 1.4x-S Rear Converter from the review page for the TC

Last edited by monochrome; 03-15-2020 at 07:38 AM.
03-15-2020, 06:37 AM   #11
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this might help explain why:

QuoteQuote:
Pentax-DA 1.4x AW AF Rear Converter
DA 1.4x and A 1.4X-L Compared
For this test we used our FA* 300mm F2.8 lens paired with the DA 1.4x converter and the A 1.4X-L converter, respectively. We compare these images with an upsampled image shot witout a converter.. . . .

The A 1.4X-L Rear Converter is slightly better that the DA 1.4x converter in terms of resolution. This is not that surprising, since this A-series converter was sold as a matching converter to the FA* 300mm F2.8 lens, and it is optimized for telephoto lenses. But the difference compared to the DA 1.4x converter is small, and we are pleased to see that the DA converter is up there with the best in image quality. The DA converter also exhibits a bit less purple fringing, which can be attributed to its newer HD coating.

The upsampled image cannot compete with either of the teleconverters, so using any one of the two tested rear converters is preferable to upsampling.

Note that the A1.4X-L rear Converter cannot be used with most lenses including the DA*300mm lens due to the converter's protruding front element. Thus, the DA converter is much more versatile than the older A1.4x-L converter.

Read more at: Pentax-DA 1.4x AW AF Rear Converter Review - DA 1.4x and A 1.4X-L Compared | PentaxForums.com Reviews
03-15-2020, 06:46 AM   #12
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Another pair of observations:
1) 1.4X converters of any kind will almost always provide more satisfactory IQ than a 2X converter, although I did use one 2X that provided very good results (a Nikon 2X designed for long lenses used on a Nikon 500mm f4.0)
2) The Pentax 400mm f5.6 is not noted as an especially sharp lens, especially wide open, so I'm doubtful that IQ with any converter will much better than marginally acceptable even closed one stop, which would be f11 with a 1.4X.
03-15-2020, 07:22 AM - 1 Like   #13
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QuoteOriginally posted by monochrome Quote
All other lenses above 300mm are specifically listed as NOT supported for the A 1.4x-S Rear Converter,. See links below.
...
Not Supported lenses for the A 1.4x-S Rear Converter from the review page for the TC
Looking back on it, that seems such an odd claim by Pentax. The A 1.4x-S obviously will fit any of the telephoto lenses, but I guess Pentax wanted to steer folks to the A 1.4x-L for the long teles and also discourage use of the non-AF converter with AF lenses (F/FA * 300/4.5).

The "S" is pretty good, but the "L" is so good I own two
03-15-2020, 07:30 AM   #14
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QuoteOriginally posted by WPRESTO Quote
1) 1.4X converters of any kind will almost always provide more satisfactory IQ than a 2X converter, although I did use one 2X that provided very good results (a Nikon 2X designed for long lenses used on a Nikon 500mm f4.0)
I recall reading some time ago a comparison of Nikon 1.4x, 1.7x, and 2x TC's. IIRC, the author concluded that the 2x TC had a "resolution penalty" of 25%, and then of course there are the additional image-degrading factors such as magnified aberrations and the necessity (usually) of increasing the ISO to accommodate the 2-stop light loss.

Do you still have photos you took with the Nikon 500/4 + 2x TC?
03-15-2020, 07:32 AM   #15
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Another BTW: The lenses & accessories list that came with my LX commented on the potential combination of a 400mm f5.6A and either 1.4XL or 2XL converter "better results are possible," somewhat vague advice that I interpreted as indicating that the combinations were not entirely satisfactory.

---------- Post added 03-15-20 at 10:38 AM ----------

QuoteOriginally posted by luftfluss Quote
I recall reading some time ago a comparison of Nikon 1.4x, 1.7x, and 2x TC's. IIRC, the author concluded that the 2x TC had a "resolution penalty" of 25%, and then of course there are the additional image-degrading factors such as magnified aberrations and the necessity (usually) of increasing the ISO to accommodate the 2-stop light loss.

Do you still have photos you took with the Nikon 500/4 + 2x TC?
Yes. I used that combo almost exclusively to photograph the nesting woodpeckers, and I do have scans of several of the chromes. I took many 36 exposure rolls over the weeks between nest building and disappearance of the surviving fledglings. I've posted most of the best scans, but I'll dig out a couple to post here. RE: the scans are never as good as the original chromes, both color and resolution suffer significantly in translation.
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