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Old Jun 9, 2018, 9:09 AM   #1
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Default New K-1 user thoughts

Hi everyone, checking in after some time away. I made the jump to full frame by obtaining the K-1 (not the mark II), and felt like leaving a few initial thoughts. The initial idea is to take it up the mountains and record a shot of the milky way Iíve had in mind for a number of years now. Full frame should improve the quality of the night / astro shots and looking forward to see how it will perform.

It took some careful thinking to choose an FF lens. On a personal level the k-5 with a 30mm f1.4 lens is a proven combination, and Iíd be looking for a similar angle, so about 50mm. To justify the jump to full frame the lens of choice needed to be as fast as possible and of high quality wide open. I couldnít find any in the 50mm vicinity that met those requirements (limited FF lens choice is a pentax thing I guess). Eventually the most promising were the pentax smc 31mm f1.8 limited, the sigma 35mm 1.4 art or for versatility the pentax 24-70 f2.8. I went with the 31mm f1.8 limited. Now that the package has come in, Iím quite positive Iíve struck gold.. With the K-5 itís been a struggle to achieve 100% infinity focus for my astrophotography. Trial and error with no aids like focus peaking. The 31mm f1.8 focus ring seems to mechanical stop exactly at infinity and the quality at f1.8 blows me away. The K-1 comes with focus peaking so astrophotography should be easier now.

One thing I was eager to find out is how my crop lenses would do on the full frame. So here we go:

Sigma dc 50-150 f2.8 II: camera freezes completely, so much that the battery needs to be removed to turn it off. Looking through the viewfinder, continued heavy vignetting remained throughout the zoom range.
Sigma dc 17-50 f2.8: Camera doesnít freeze fortunately, but again continued heavy vignetting throughout the zoom range.
Sigma dc 30mm f1.4: Heavy vignetting, but Ďalmostí useable (examples to follow).
Pentax 10-17 f3.5-4.5 fish-eye: FF image circle covered from 15mm upwards, which will leave f4.5 max aperture.

The results lead me to believe that variable aperture zoom lenses for crop sensors are the most potent for full frame, because they actually enlarge the image circle when zooming in. But of course theyíll be slow.

Some samples of the crop lenses in FF mode:

sigma dc 30mm @ f1.4 (max aperture)


sigma dc 30mm @ f5


sigma dc 30mm @ f10


sigma dc 30mm @ f16 (min. aperture)


pentax 10-17 @ 10mm f3.5


pentax 10-17 @ 15mm f4 (on the very border to 4.5)


pentax 10-17 @ 17mm f4.5
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Old Jun 14, 2018, 9:14 AM   #2
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Cool! Iíve used the DA 15 Ltd in both FF and crop mode on the K1, and both can be fun. The vignetting can be rather fun for certain things, though I usually use it in crop mode. I love your pictures with the 10-15, I hadnít bothered with it on the K1.

I also have a SMC 24 mm f2.8 that works very nicely if you donít mind manual lenses.

Thereís some 3rd party wide angle lenses that are now getting some attention, too.
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Old Jun 23, 2018, 12:17 PM   #3
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Great post!

Very interesting with the Sigma DC 30mm f/1.4.

I actually have a Sigma DC 30mm f/1.4 in a Nikon F mount. The series at different f settings is quite informative. I might have to give that lens a go on my Nikon D750.

As for the fisheye . . . I happen to have that lens. I can't remember if the blocked areas are from the built-in lens hood or internal baffles. I did read somewhere someone cutting off the built-in lens hood to use the fisheye on a FF.

I look forward to your shots with your 31mm f/1.8!
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Old Jul 5, 2018, 9:09 AM   #4
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Thank you!

@mtngal I'd certainly be interested to try some of the full frame glass from the analog age. Also the irix 15mm has caught my attention and seems to be of decent quality.

@tacticdesigns hardware mods aren't really required to use the 10-17 in ff mode, just have to zoom in to about 15 or 16mm and the circle will be covered. But it's always nice to see what can be achieved through some more drastic mods.
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