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08-07-2010, 08:56 AM   #1
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The hunt for a fast lens.

What is the fastest lens (auto or manual) that can be attached to a K10/K20/K7 (K mount), with or without a mount adapter ?

It's not to hard to find f1.4's, but do there exist something like 1.2 or even 1.0 ?
If so, are the lenses any good or do they become too soft ?

The reason for this is a hunt for a good indoor, no-flash-needed, lens. Preferably (or most likely) a prime (manual or not) with an focal length somewhere in the range between 20 and 40mm.

It's strange IMO that there seems to be so few really fast and wide (around 30mm) lenses. Most of the fast ones have focal length's in the portrait range (50mm +).

08-07-2010, 09:05 AM   #2
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Problem is even if they existed, at 1.2 or 1.0 the DOF would be so thin, only practical for special-effect shots.

Combination of wide and fast makes a lens huge & expensive. The fastest wide I know of is the Sigma 20/1.8

PS: I guess the combination of tele and fast also makes a lens huge :-) thus we see sub-2.0 lenses mostly in the 30-50 range.

Last edited by Kguru; 08-07-2010 at 09:14 AM.
08-07-2010, 09:23 AM   #3
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There's the K50/1.2 and M35/1.4, and various 3rd-party glass in the f/1.2-1.5 range around 24mm and 58mm and 85mm. Lenses that fast are very difficult to focus wide-open -- but I'd sure like to have some! If you're adventurous, you can buy a simple 40mm (focal length and diameter) lens cheap from an optical supplier like Edmund Scientific, mount it on a helicoid, and have the fastest glass in town. It's uncorrected, of course, so CA etc will be terrible. But at f/1.0, with 99% of the image OOF, who cares? HINT: For a similar effect, use a fast (f/1.4-2) 85mm lens with a +1 or +2 diopter close-up adapter.
08-07-2010, 09:35 AM   #4
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pentax made some f1.2 primes that you can find in the lens database. all manual focus. Lowest price on ebay about $400.

Fast lenses are of limited use in my opinion. I shoot promo pics for a play threatre in which we are not allowed to use flash. A fast aperture forces one into a narrow DOF which puts more pressure on accurate focus, and also limits the number of actors that can be shown sharp across the stage.

Of far more practical use is a high ISO camera body such as the Kx, My K20, i get by in dark scenes by shooting up to iso 3200 and 6400 using LR3 and if necessary, Topaz 4 or later. F2.8 is about the fastest one needs, although my f1.4 50 will AF in some low light where a f2.8 lens won't.

08-07-2010, 10:14 AM   #5
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The Sigma 30mm f/1.4 is an excellent lens, is AF, and is very sharp at 1.4 as well...

c[_]
08-07-2010, 10:26 AM   #6
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There is a HUGE misunderstanding regarding low light photography and fast glass.

First things first, unless you want a razor thin depth of field stylistically, you should never shoot wide open!

The reason fast glass is good in low light is that it brings the lens' sweet-spot out of the f/8 range and into the f/4 or so range, which you should shoot at and make up the difference with your ISO.

Any lens faster than f/1.4 (or even f/2.8 in most cases) are designed that way for those seeking the effects you can achieve with the depth of field and not for low-light photography.
08-07-2010, 10:40 AM   #7
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QuoteOriginally posted by RioRico Quote
There's the K50/1.2 and M35/1.4, and various 3rd-party glass in the f/1.2-1.5 range around 24mm and 58mm and 85mm. Lenses that fast are very difficult to focus wide-open -- but I'd sure like to have some! If you're adventurous, you can buy a simple 40mm (focal length and diameter) lens cheap from an optical supplier like Edmund Scientific, mount it on a helicoid, and have the fastest glass in town. It's uncorrected, of course, so CA etc will be terrible. But at f/1.0, with 99% of the image OOF, who cares? HINT: For a similar effect, use a fast (f/1.4-2) 85mm lens with a +1 or +2 diopter close-up adapter.
Yes the M35/1.4 would be a fast lens that I would love to own. Unfortunately like the K8.4/2.8 Fish-Eye, they were only prototypes or only a couple ever produced. So these two lenses fall into the “in my dreams” category". They’re like some rare silver dollar that only two known copies exist and both are in museums. In this case it’s a mystery who owns either of these two Pentax lenses.
Phil.
08-07-2010, 11:13 AM   #8
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It all really depends on your application, all the lenses I use on a regular daily basis are considered to be classified as fast for their respective focal lengths, examples; SMC Pentax-A 50mm F1.2, SMC Pentax-A* 85mm F1.4, SMC Pentax-A* 135mm F1.8, SMC Pentax-A* 200mm F2.8 ED. It all depends on how and what you want and need to do, in any given situation.

As always, most lenses perform better when stopped down a stop or two, but there are real world situations that will not allow this and sometimes shooting wide open is the only route. For me that's music concert photography, where there is no flash allowed and ISO is already cranked to the max.

Remember the viewfinder always looks brighter with fast lenses and for manual focusing in low light situations, trust me, that's needed due to the much reduced DOF, which can be wafer thin is some cases.

But hey, that's just my world.


Last edited by Kerrowdown; 08-07-2010 at 11:26 AM.
08-07-2010, 01:05 PM   #9
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QuoteOriginally posted by RioRico Quote
There's the K50/1.2 and M35/1.4, and various 3rd-party glass in the f/1.2-1.5 range around 24mm and 58mm and 85mm. Lenses that fast are very difficult to focus wide-open -- but I'd sure like to have some! If you're adventurous, you can buy a simple 40mm (focal length and diameter) lens cheap from an optical supplier like Edmund Scientific, mount it on a helicoid, and have the fastest glass in town. It's uncorrected, of course, so CA etc will be terrible. But at f/1.0, with 99% of the image OOF, who cares? HINT: For a similar effect, use a fast (f/1.4-2) 85mm lens with a +1 or +2 diopter close-up adapter.
they can be tricky as far as DOF is concerned. can be difficult but not impossible. you need to have some nice skills with regards to focusing and working the lens to it's full potential. usually the difficult part would be focusing at MFD where the working area is very thin and achieving focus is tricky and hard work. although if you nail one, the rewards are great and spectacular. this is also why such lens are called specialty lenses, not because they can be only be used for one particular type of photography where it excels, but also because it would take a specialist to use a very skill demanding lens in a skill demanding situation.

anyway, at midrange or infinity, the lens is not that difficult to achieve focus. as far as using a 50/1.2 and 85/1.4 is concerned, I find it more difficult to achieve or nail focus with the 85 compared to the 50.

adding a diopter lens to an 85, may produce the same DOF effect, although you would have compromises like degrading IQ and losing infinity, which would render the lens useless for it's intended real purpose. at the end, it would more serve as a macro instead.
08-07-2010, 01:08 PM   #10
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QuoteOriginally posted by RioRico Quote
There's the K50/1.2
QuoteOriginally posted by philbaum Quote
pentax made some f1.2 primes that you can find in the lens database. all manual focus. Lowest price on ebay about $400.
Focal length a little too narrow but I'm looking for this one.


QuoteOriginally posted by RioRico Quote
If you're adventurous, you can buy a simple 40mm (focal length and diameter) lens cheap from an optical supplier like Edmund Scientific, mount it on a helicoid, and have the fastest glass in town. It's uncorrected, of course, so CA etc will be terrible. But at f/1.0, with 99% of the image OOF, who cares? HINT: For a similar effect, use a fast (f/1.4-2) 85mm lens with a +1 or +2 diopter close-up adapter.
Uhmm.. I obviously have to do a little research here.

QuoteOriginally posted by philbaum Quote
Fast lenses are of limited use in my opinion. I shoot promo pics for a play threatre in which we are not allowed to use flash. A fast aperture forces one into a narrow DOF which puts more pressure on accurate focus, and also limits the number of actors that can be shown sharp across the stage.

Of far more practical use is a high ISO camera body such as the Kx, My K20, i get by in dark scenes by shooting up to iso 3200 and 6400 using LR3 and if necessary, Topaz 4 or later. F2.8 is about the fastest one needs, although my f1.4 50 will AF in some low light where a f2.8 lens won't.
QuoteOriginally posted by noahpurdy Quote
There is a HUGE misunderstanding regarding low light photography and fast glass.

First things first, unless you want a razor thin depth of field stylistically, you should never shoot wide open!

The reason fast glass is good in low light is that it brings the lens' sweet-spot out of the f/8 range and into the f/4 or so range, which you should shoot at and make up the difference with your ISO.

Any lens faster than f/1.4 (or even f/2.8 in most cases) are designed that way for those seeking the effects you can achieve with the depth of field and not for low-light photography.
The two posts above shoot the same dog. The CCD sensitivity dog. Bah. The human brain understands DOF and fill out the Bokeh. The image becomes natural, even if only 0,01 of the picture is in focus. Noise, on the other hand , ruins everything. Even a single misplaced pixel. So no, I don't take the "make the chip more sensible" road. My K7 is set at ISO100 and stays there (wish I could use that button for something else).

QuoteOriginally posted by ll_coffee_lP Quote
The Sigma 30mm f/1.4 is an excellent lens, is AF, and is very sharp at 1.4 as well...

c[_]
I got the Sigma. Sloppy in the edges, quite good in centre. I'm after something with even lesser DOF.

QuoteOriginally posted by kerrowdown Quote
As always, most lenses perform better when stopped down a stop or two, but there are real world situations that will not allow this and sometimes shooting wide open is the only route. For me that's music concert photography, where there is no flash allowed and ISO is already cranked to the max.
A flash ruins everything. Situation photography is about capturing the light there is, not replacing it. The ISO button is not an alternative, "noise" (or starved CCD pixels) is not tolerated.
QuoteOriginally posted by kerrowdown Quote
Remember the viewfinder always looks brighter with fast lenses and for manual focusing in low light situations, trust me, that's needed due to the much reduced DOF, which can be wafer thin is some cases.
I got the Sigma f1.4 and I'm pretty used to using the lens release button (allows MF when needed). The KatzEye helps.
08-07-2010, 01:26 PM   #11
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QuoteOriginally posted by tiltman Quote
The two posts above shoot the same dog. The CCD sensitivity dog. Bah. The human brain understands DOF and fill out the Bokeh. The image becomes natural, even if only 0,01 of the picture is in focus. Noise, on the other hand , ruins everything. Even a single misplaced pixel. So no, I don't take the "make the chip more sensible" road. My K7 is set at ISO100 and stays there (wish I could use that button for something else).
Your loss.
08-07-2010, 02:32 PM   #12
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QuoteOriginally posted by tiltman Quote
My K7 is set at ISO100 and stays there (wish I could use that button for something else).
Wow, I wish I could get away with 100 ISO, but for me it is not possible in the lighting conditions I'm working with. I'm afraid it's always iSO 800, 1600, 3200 or more at a push, and that's still only giving shutter speeds of 30th, 60th and maybe 125th on a good day.

QuoteOriginally posted by tiltman Quote
A flash ruins everything. Situation photography is about capturing the light there is, not replacing it.
That's what I said, in my line of work, the venues will not allow flash, full stop. That's why other work rounds have to be found, fast lenses and high ISO's.

QuoteOriginally posted by tiltman Quote
The KatzEye helps.
Yep Katzeyes are essential equipment, all my cameras are fitted with them, I never leave home without 'em.
08-07-2010, 03:15 PM   #13
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QuoteOriginally posted by Pentaxor Quote
QuoteOriginally posted by RioRico Quote
HINT: For a similar effect, use a fast (f/1.4-2) 85mm lens with a +1 or +2 diopter close-up adapter.
adding a diopter lens to an 85, may produce the same DOF effect, although you would have compromises like degrading IQ and losing infinity, which would render the lens useless for it's intended real purpose. at the end, it would more serve as a macro instead.
A +1 diopter on an 85 drops the far-focus from infinity to about 1.2m and, on my Nikkor 85/2, drops the close-focus from 0.85m to about 0.4m. That puts it within portrait-closeup range, and slices the DOF rather thin. It's a specialist approach.
08-07-2010, 03:30 PM   #14
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QuoteOriginally posted by noahpurdy Quote
Your loss.
QuoteOriginally posted by kerrowdown Quote
Wow, I wish I could get away with 100 ISO, but for me it is not possible in the lighting conditions I'm working with. I'm afraid it's always iSO 800, 1600, 3200 or more at a push, and that's still only giving shutter speeds of 30th, 60th and maybe 125th on a good day.
... To be honest, I use several cameras when shooting sceenes. The one with need for a very large aperture (or small in numbers) is the "sense / feeling / sensation" (wow, this is hard to explain in a foreign language) one , the documentary one use ISO and flash as needed (no problems there).
QuoteOriginally posted by kerrowdown Quote
That's what I said, in my line of work, the venues will not allow flash, full stop. That's why other work rounds have to be found, fast lenses and high ISO's.

Yep Katzeyes are essential equipment, all my cameras are fitted with them, I never leave home without 'em.
Yes... Uhumm... Revelation.
I started without one and had a really hard time MF'ing. I did photography in the 80's (education and all the stuff) then stopped and did somethng else (computer programming) for a long time. Then I (in 2007) did buy a K10d and was hooked ... I blamed the poor MF results on the age until I did discovered the katzeye.

Last edited by tiltman; 08-07-2010 at 03:59 PM.
08-07-2010, 05:17 PM   #15
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I really think that you're limiting your options by leaving the ISO at 100. Most modern DSLRs are extremely capable of taking good shots at much higher ISOs than that, including yours.

I've just returned from a course which included portrait work using available light only, and most of the shots were taken at f/2.8, occasionally f/4, and the ISO was adjusted as necessary, with some being at 800 and a couple at 1600. And this was using K20D bodies, not the newer models. The shots were excellent, and although there were one or two with a bit of "graininess" to them (no more than you used to get with fast film), this can be removed very easily using plugins such as Topaz, Nik, or in my case, Noise Ninja. I have all three of those, but for me, Noise Ninja does it best - but, your mileage may vary.

I'm not sure why you'd want to be keeping the ISO at 100 for some theoretical purist reason - it's like driving a Ferrari with the handbrake on...!
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