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05-28-2012, 02:14 PM   #1
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Pentax K 50 mm f1.2 on K-5

I've been meaning to acquire one of these nice lenses, but I've been reading that you can only use it at 1.2 on the K-5? Is that really true, and if yes, why is it, and may there be a workaround? I mean I'd probably be shooting at 1.2 most of the time anyway..but still. Would be nice to have the options!

05-28-2012, 02:19 PM   #2
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The camera doesn't know what aperture you are using when you are using a KM lens. All the camera knows is that you have the SR set to 50mm and that the lens doesn't have electrical contacts for aperture information.

When you use the Green Button to meter the camera uses the available light coming through the lens.

Focusing at 1.2 may be difficult with the default focusing screen, because it is optimized for slow AF lenses. Anything faster than f3.5 doesn't display the correct DOF.
05-28-2012, 02:24 PM   #3
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QuoteOriginally posted by iyun Quote
I've been meaning to acquire one of these nice lenses, but I've been reading that you can only use it at 1.2 on the K-5? Is that really true, and if yes, why is it, and may there be a workaround? I mean I'd probably be shooting at 1.2 most of the time anyway..but still. Would be nice to have the options!
You will have to enable the aperture ring from the setup menu. Once that is done, you can meter and shoot quite nicely using the aperture of your choosing in M mode using stop-down (green button) metering. As noted above, the stock focus screen has inadequate precision for manual focus with fast lenses. I would suggest an aftermarket focus screen with split-image or microprism focus aid.


Steve
05-28-2012, 02:26 PM   #4
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Your information is untrue. The truth is that you are only able to use it wide open in AV mode. To use it at any aperture, switch to M mode. You also have some semi-automated exposure, which is the green button if you customize it to do so (camera settings - TV shift). It can stop the lens down and estimate the shutter speed required.

05-28-2012, 03:00 PM   #5
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QuoteOriginally posted by kcobain1992 Quote
Your information is untrue. The truth is that you are only able to use it wide open in AV mode. To use it at any aperture, switch to M mode. You also have some semi-automated exposure, which is the green button if you customize it to do so (camera settings - TV shift). It can stop the lens down and estimate the shutter speed required.
You are absolutely correct regarding the behavior in Av mode, though aperture ring support must still be enabled, even in M mode, when using a non-A contact lens such as the K 50/1.2. (See pages 338 and 339 of the K-5 manual.) If not enabled, the shutter will not even release. As for metering...you can use the optical DOF preview for stop-down metering. The green button should also work to set shutter speed for a particular set aperture. (I don't own the K-5, but believe that to be the default behavior in M mode for all Pentax dSLR bodies that have the green button.)


Steve

Last edited by stevebrot; 05-28-2012 at 03:07 PM.
05-28-2012, 03:01 PM   #6
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A really cool feature I only recently discovered that changed the way I use non-A lenses is the fact that you can use the optical preview to activate a light meter in M mode. On the K-5 and similar bodies there is a specific optical preview dial for this, but the K-x can use the green button for the same purpose. You choose your aperture, stop the lens down with the optical preview and then you can have finer control of the exposure, as you can see the meter readings changing as you alter your frame.

Green button metering is faster, but I always felt it was taking something away from me, which I wanted to avoid in manual mode. Using this method is very similar to metering on an old film camera like the ME Super. It's very simple and useful, and it's incredibly involving too.
05-28-2012, 03:07 PM   #7
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My K50/1.2 has a nice home on my K20D, along with many other M-type lenses. Yes, aperture ring usage must be enabled. Yes, it only shoots wide-open in Av mode. [Setting any Auto mode defaults to Av with a non-A-type or non-AF lens.] Yes, in M mode, the Green button stops-down M-type lenses for metering and exposure. Yes, focusing close at f/1.2 can be tricky. I have tricks.

* For focus, I use CIF (catch-in-focus), sometimes with Continuous Drive for spray-and-pray action. A cheap katzeye-clone split-focus screen helps with well-lit contrasty subjects, lets me know I'm close; the Focus Confirmation green hex tells me I'm there; and CIF nails the shot.

* For aperture control, I'll set the Mode dial at TAv (right next to M on my K20D) with the lens stopped-down to f/5.6 or whatever. As long as I'm in TAv (which defaults to Av) the lens is wide-open. If I need more DOF in a hurry, I quick-flick the Mode dial to M and hit the Green button, *without* fiddling around with the aperture ring. That saves time and doesn't distract my attention.

We don't use superfast lenses wide-open for edge-to-edge flatfield sharpness. We use them to grab shots that are otherwise impossible. Superfast lenses *do* render beautifully and with great sharpness when stopped-down, so they're much more flexible than plebian f/1.7 and f/2.8 and f/4 glass. And when DOF at 50/1.2 isn't thin enough, I put a screw-on Sony VCL-1546A 1.5x tele-adapter on the front, making it a 75/1.2 optic. Ooh ooh! That's great for headshots where I want one eyeball sharp and everything else (eyelashes included) soft and dreamy.

I sure hope the K3-FF comes with a DFA 50/1.2. Not that I could afford them...

QuoteOriginally posted by Mareket Quote
A really cool feature I only recently discovered that changed the way I use non-A lenses is the fact that you can use the optical preview to activate a light meter in M mode. On the K-5 and similar bodies there is a specific optical preview dial for this, but the K-x can use the green button for the same purpose. You choose your aperture, stop the lens down with the optical preview and then you can have finer control of the exposure, as you can see the meter readings changing as you alter your frame.
I get this on my K20D also, with ANY lens in M mode, in Optical Preview. (See p.115 in the K20D manual.) Switch to M, and a lightmeter bar appears at the bottom of the VF. I may still hit the Green button for an initial reading, but then I can keep my eye on the VF and spin dials and watch the lightmeter till I'm happy, with no distractions. Like I said, this works with any lens, not just an M-type.

EDIT: The above is corrected. Again.

Last edited by RioRico; 05-28-2012 at 10:08 PM.
05-28-2012, 03:52 PM   #8
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Thanks for this valuable information.

05-28-2012, 04:43 PM   #9
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QuoteOriginally posted by RioRico Quote
I get this on my K20D also, with ANY lens in M mode. Switch to M, and a lightmeter bar appears at the bottom of the VF. I may still hit the Green button for an initial reading, but then I can keep my eye on the VF and spin dials and watch the lightmeter till I'm happy, with no distractions. Like I said, this works with any lens, not just an M-type
So when you put an M lens on your K20D in M mode you see a light meter without having to use optical preview? Does it just go off wide open readings? i.e. you have to compensate yourself for different apertures? If so that's very handy. The K-5 will show a light meter for any A lens or later without stopping down, but you have to stop down to see a meter for anything earlier.
05-28-2012, 06:14 PM   #10
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I shoot my K50/1.2 exclusively in Av mode on my K-5, if I want f/1.4 or smaler I'll use a FA50. The e-SS screen is terrific for this lens, it's meant I don't use live view anymore and focus it exclusively through the OVF.

Last edited by twitch; 05-28-2012 at 11:11 PM.
05-28-2012, 08:51 PM   #11
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QuoteOriginally posted by Mareket Quote
So when you put an M lens on your K20D in M mode you see a light meter without having to use optical preview? Does it just go off wide open readings? i.e. you have to compensate yourself for different apertures? If so that's very handy. The K-5 will show a light meter for any A lens or later without stopping down, but you have to stop down to see a meter for anything earlier.
Hmm, good question, let's see... Nope, I was wrong, and I'll correct the prior post. The lightmeter appears with A-type or AF lenses only, not with lenses lacking 'A' contacts.
05-28-2012, 09:20 PM   #12
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QuoteOriginally posted by RioRico Quote
The lightmeter appears with A-type or AF lenses only, not with lenses lacking 'A' contacts.
Are you sure? On my K10D, I get the meter bars with optical preview in M mode for all lenses.


Steve
05-28-2012, 10:03 PM   #13
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QuoteOriginally posted by stevebrot Quote
QuoteOriginally posted by RioRico:
The lightmeter appears with A-type or AF lenses only, not with lenses lacking 'A' contacts.
Are you sure? On my K10D, I get the meter bars with optical preview in M mode for all lenses.
With AF DA18-250 on K20D: lightmeter
[/me pulls out drawer full of 28s]
With A-type TOU 28/2.8: lightmeter

With SMC-M28/2.8: no lightmeter
With modded N/AI Vivitar: no meter
With M42 Accura Diamatic: no meter

Et cetera. No matter if the body contacts are shorted or not. Without 'A' contacts on the lens, no lightmeter. Oh bother.

But maybe I'm doing something wrong. Let me check the manual on Optical Preview... [/me studies quickly] Ah, I see it! I'm set for LiveView, not Optical Preview! I never use Optical Preview! Four bloody years with the K20D, and I've never had reason to use Optical Preview! [/me slaps forehead]

Ok, I'll re-check those lenses... Yeah, the lightmeter appears. But my eyes aren't good enough to see image details whilst the lens is stopped-down. Maybe that's why I've never bothered with Optical Preview. OK, I'll go back and correct that prior post again. Grumble grumble...

And then I get to swap the functions of the two dials so I can change shutter speed whilst holding the preview lever. Wait, can I even do that? [/me is tired but rereads manual anyway] Oh good, it's Custom Menu item #24. Ok, that's taken care of. Now I need more painkillers.

Last edited by RioRico; 05-28-2012 at 10:15 PM.
05-28-2012, 11:08 PM   #14
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thanks for all the great info guys!!

going to get this lens
05-29-2012, 12:14 AM   #15
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QuoteOriginally posted by RioRico Quote
...
And when DOF at 50/1.2 isn't thin enough, I put a screw-on Sony VCL-1546A 1.5x tele-adapter on the front, making it a 75/1.2 optic.....
The tele-adapter will lose light though ?
Pete

Last edited by Transit; 05-29-2012 at 12:47 AM.
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