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03-31-2012, 10:01 PM   #1
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Lenses For K-01

A total noob here.
I have 3 Sigma K mount lenses:
Sigma DC 17-70 mm 1:2.8-4.5
Sigma DC 18-200 mm 1:3.5-6.3
Sigma DG 70-300 mm 1:4-5.6
Will they work as intended?
Will the focal length be the same as maked on the lense?
Thanks
Walter

03-31-2012, 10:42 PM   #2
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Yes and yes. Focal length never changes

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03-31-2012, 10:58 PM   #3
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QuoteOriginally posted by seasdes Quote
Will they work as intended?
Will the focal length be the same as maked on the lense?
As Adam said, focal lengths don't change. They neither stretch nor shrink when moved amongst cameras. If you're not an experienced 35mm film photographer transitioning to APS-C, forget you ever heard of crap crop factors. The marketing terms equivalence and crop factor cause endless confusion. All that's happening is that smaller-frame cameras see less of a projected image than do larger-frame cameras. The camera crops the frame; the lens gets the blame.

But while the lenses remain the same, there *is* a usage difference. The DOF (depth of field) scales marked on the lenses are for their use on FF (full-frame) cameras, not on crop-sensor cameras like your K-01. The DOF scales on your zooms are probably a bit hard to read anyway, and can pretty much be ignored. But if you ever get FF prime (fixed focal length) lenses for your K-01 and wish to indulge in zone-focus, you'll need to adjust the scales a little.

But that's something to deal with later. For now, have fun!
04-01-2012, 03:07 AM   #4
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Your lenses will give the picture that is exactly the same as is to see on the screen on the back of your K-01.

The 300mm lens may be a little slow in focussing since it is a f5.6 lens not giving to much light to the sensor for focussing. But maybe not to bad after all on a sunny day.

04-01-2012, 06:22 AM   #5
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All Pentax DSLRs and the K-01 have APS-C sensor that have a 1.5x crop factor compared to using them on Pentax 35mm SLRs so a 28mm lens has a wide angle FOV on a 35mm SLR but with Pentax DSLR/K-01 1.5x crop factor equals a 42mm normal angle FOV. Canon's smaller APS-C (7D etc) sensor has an even larger 1.6x crop factor. My 15mm F2.8 Sigma FF fish-eye lens has a 180 deg FOV on a Pentax 35mm SLR but on a Pentax DSLR /K-01 it has a much smaller FOV and has a FOV more like a 22.5mm wide angle lens on a 35mm SLR.

http://www.abelcine.com/fov/

Pentax made two fish-eye zooms , one for 35mm SLRs and one for Pentax APS-C DSLRs :

F 17-28/3.5-4.5 Fish-Eye :
http://kmp.bdimitrov.de/lenses/zooms/short/F17-28f3.5-4.5-Fish.html

DA 10-17/3.5-4.5 Fish-Eye ED [IF]:
http://kmp.bdimitrov.de/lenses/zooms/short/DA10-17f3.5-4.5-Fish.html

Both cover the maximum 180 deg FOV.
QuoteQuote:
The smc Pentax-F 17-28mm was designed for film cameras where it at 17 mm covers 180 degrees diagonally. On the Pentax digital SLRs the coverage is much less, actually just a little bit more than a rectilinear 15mm lens, which still is respectable.
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/164-review-sup...3-5-4-5-a.html

Last edited by jogiba; 04-01-2012 at 07:42 AM.
04-01-2012, 07:50 AM   #6
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QuoteOriginally posted by seasdes Quote
Sigma DG 70-300 mm 1:4-5.6

I also agree with what Mr. Hendriks stated; that the 6.3 will pose a slight issue with focusing under some (but not all) lighting conditions. Also noting... The K-01 (as noted on the viewscreen image) will not take an autofocus pic without having a focus lock-on, but... One can always switch over to the manual focus settings and also have the option of using focus peaking.

At 5.6 (max focal length, most open aperature) there may be some problems, but they would be a lot less than the 6.3...

It would be great to see any camera system have perfect functionality between all available lens' and camera bodies,but... That would also explain why I've seen such (physically) large lens' <and expensive ones> on the K-01.

Also a bit off topic... Anyone see any issues with filter vignetting on any lens' for the K-01?? Especially the wider full frame image (yes, not full frame sensor) lens'?
04-01-2012, 08:15 AM   #7
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QuoteOriginally posted by seasdes Quote
A total noob here.
QuoteOriginally posted by jogiba Quote
All Pentax DSLRs and the K-01 have APS-C sensor that have a 1.5x crop factor compared to using them on Pentax 35mm SLRs
OP is a "total noob". I interpret that as: no 35mm camera experience. So crap.factor is meaningless here. N00bs are subject to enough confusion without having this also.

QuoteOriginally posted by Medium FormatPro Quote
Anyone see any issues with filter vignetting on any lens' for the K-01?? Especially the wider full frame image (yes, not full frame sensor) lens'?
We wouldn't expect such vignetting exclusively with the K-01. If any lens vignettes on any APS-C camera, then the K-01 is equally susceptible. But vignetting is part of the design of certain lenses: full-circle fisheyes. Frame-filling fisheyes, like old 16-17-18mm lenses and modern 8-10mm glass, shouldn't vignette on any frame with a diagonal of 43mm or less.
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