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02-01-2011, 01:28 PM   #1
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The K5 and need for fast primes

Hi!
I have just started using the K5 and I am amazed by its low light capabilities. Is the need for fast primes, for instance sub F2 primes really needed for this camera? As far as I know few primes perform at its best when shooting with larger aperture than F2.
So my question is are fast primes really necessary with this camera? When taking cost into consideration is it worth spending extra money on super fast primes or would an F2.8 prime do the job?
When I look at the Pentax prime range few primes have larger aperture than F2. Any thoughts on this?

02-01-2011, 02:00 PM   #2
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Well perhaps "necessary" is not the right word, it depends what kind of photography you do. If you mainly do landscapes in daylight you don't need them at all
The benefits of a fast lens go beyond lowering the iso. Even with the K-5 you may want the reduced depth of field only faster lenses can offer. Or you may want/need to shoot in very low light.
I see what you mean, lots of people won't feel the need for a faster lens as the pictures are so good at 6400 iso or more. My guess is that people who are not into photography will first blame the camera rather that the lens if they get ugly noisy pics. Iso performance is advertised a lot more than expensive lenses with "weird numbers"
02-01-2011, 02:12 PM   #3
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Yes I absolutely see the need for shallow dof composition wise. Personally I mostly shoot people and find sub F2 not that useful. Well that is not quite true I love shooting with shallow dof!
However since i got the K5 technically I dont need flash in order to get a decent indoor shot. Using ISO 6400 and aperture close to F2 there is no problem. The problem however is that indoor lightning tends to be unsuitable composition wise. Portraits taken indoor in the evening in the light of lamps often gives unwanted shadows on the subject. Using a flash gives a much better result. And this leads yet again to the conclusion that fast primes are not that needed anymore.
02-01-2011, 02:35 PM   #4
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I think f/2 or f/2.4 primes would likely be fast enough if they performed well wide open. I usually shoot my sub f/2 primes in this range, anyway. F/2.8 seems to me to be a sweet spot on Aps-c for the combination of narrow DOF and sharpness, sort of like what f/4 is on full frame.

02-01-2011, 02:39 PM   #5
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You need it for some pictures I guess.

DA*55mm at f1.4, but not so great in colour and a little to much sharpening (already old picture).
02-01-2011, 02:40 PM   #6
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I love fast primes, and i use a lowly KX

02-01-2011, 03:01 PM   #7
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I would expect you'd find great lens speed *less*often useful/necessary, given the higher ISO and better AF, but they still have their place, especially if you really like that very-thin DOF. I've always liked fast lenses for the snappy manual focusing, primarily, and usually like to keep em around f2 or 2.4, anyway, if possible, both for the better sharpness and cause that's about where I usually want my narrow DOF, anyway. But that's a matter of taste and all.

If you really like the really narrow DOF option, of course you'll want your faster lenses: not much getting around that.
02-01-2011, 03:52 PM - 1 Like   #8
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I forgot to mention that my shot was with a 85/1.5 helios 40 soviet tank

02-01-2011, 04:05 PM   #9
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QuoteOriginally posted by dude163 Quote
I forgot to mention that my shot was with a 85/1.5 helios 40 soviet tank
Haha I love it!

Fast primes will be not as necessary for low-light shooting, but just as necessary for soft portraits and/or creative DOF shots.

My thinking on low-light photography is keep pushing the box. If with the K-7 I can get good photos at ISO 2000 with my 58mm 1.4, just think how many even darker situations I'd be able to shoot at ISO 6400 @ 1.4 on a K5? Night street photography comes to mind.
02-01-2011, 06:34 PM   #10
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QuoteOriginally posted by MrK5 Quote
Hi!
I have just started using the K5 and I am amazed by its low light capabilities. Is the need for fast primes, for instance sub F2 primes really needed for this camera? As far as I know few primes perform at its best when shooting with larger aperture than F2.
So my question is are fast primes really necessary with this camera? When taking cost into consideration is it worth spending extra money on super fast primes or would an F2.8 prime do the job?
When I look at the Pentax prime range few primes have larger aperture than F2. Any thoughts on this?

If you want to continue with lovely bokeh shallow DOF shots, absolutely!!!!

But that aspect of shooting aside, I'm finding that I'm still using f/1.2 and f/1.4 on my K-5 to push the limits of low light shooting as far as I can.


As for your statement ....

QuoteQuote:
As far as I know few primes perform at its best when shooting with larger aperture than F2.
... what is best?

My fast primes IMO perform at their best wide open. Sharpness right across the frame isn't always 'best' - Apart from landscapes I find sharp across the frame shots boring. I like depth.

02-01-2011, 07:29 PM   #11
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Pentax and nice primes rhymes.

Pentax = practical , just pick what you *need*.

Or allow yourself the extravagance and go-get the extraordinary Samyang 85mm/f1.4 ($250 new) or the classic SMC-M 50mm/f1.4 from Pentax ($50 used). Eventually there's the Sigma 30mm/f1.4 which is AF (~ $400 new) but never owned one.

PS The SY85 will blow your socks off )) garanteed!
02-01-2011, 08:03 PM   #12
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QuoteOriginally posted by dreamfoto Quote
Pentax and nice primes rhymes.

Pentax = practical , just pick what you *need*.

Or allow yourself the extravagance and go-get the extraordinary Samyang 85mm/f1.4 ($250 new) or the classic SMC-M 50mm/f1.4 from Pentax ($50 used). Eventually there's the Sigma 30mm/f1.4 which is AF (~ $400 new) but never owned one.

PS The SY85 will blow your socks off )) garanteed!
I have a a Sigma 30/1.4 - Fantastic Lens on the K-5
02-01-2011, 09:09 PM   #13
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To get a properly exposed photo, it's probably not strictly necessary since iso now goes into the gazzillions.

To get one that is properly composed to suit your needs fast lens may be necessary.

Like everything in photography it all depends on what you are trying to accomplish. That's what dictates necessary or not.
02-01-2011, 10:31 PM   #14
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My k-5 arrived yesterday which is an upgrade for me from a K10. The improvements in low light are remarkable although they are MORE remarkable on the back of camera display than they are after I download the images and compare them on a computer screen.

IN my first review of K5 vs K10 with some morning twilight photos I'm satisified that there are several F stops of improved performance.
02-02-2011, 07:24 AM   #15
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Thanks for all the input. Nice to get so many different thoughts on the subject
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