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02-12-2012, 01:12 PM   #16
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QuoteOriginally posted by stevebrot Quote
Stop-down metering: The lens is stopped down to the taking aperture for the meter reading. The meter "sees" exactly the same light as the film. This is the type of metering used in most M42 film cameras such as the Pentax Spotmatic. Those have a small button on the body that turns on the meter while stopping down the lens. Once stopped down, the photographer adjusts shutter speed and aperture to center a needle in the viewfinder. Once set, you turn the meter off, focus, and shoot.

Open-aperture metering: The lens is at maximum aperture for the meter reading. Supporting this feature requires either a physical coupling between the aperture ring and the camera body or control of the aperture by the body.

Your K-r supports open-aperture metering with all Pentax lenses that have electrical ("A") contacts on the mount. Since it lacks the physical coupler (due to the so-called crippled mount), you have to use stop-down metering with lenses that lack the "A" contacts. With K-mount lenses, this is done by using the green button technique. Pushing the button momentarily stops the lens down to take the meter reading. With M42 lenses, you must put the lens in manual aperture mode and manually stop the lens down to take the reading.


Steve
Thank you. That helps a lot.

02-12-2012, 02:12 PM - 1 Like   #17
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How manual is manual?

Really, it is a process and not just using manual aperture lenses.

For me, going manual means you take a meter reading somehow, and then you decide the shutter and aperture to get the exposure you want.

This may be pushing the green button, using an outside light meter, or even the sunny 16 rule (sunny day, shutter speed =1/ISO at F16) and adjusting from there.

If you are simply discussing using lenses not in the A position, then metering can be still accomplished in camera, however some bodies (the K10/20 are the worse) have "unique" metering behavior as a function of aperture. My advise is to make meter readings at f4-5.6 because that seems to be where they are most accurate, and I think this is because this is the aperture range of kit lenses. Kind of makes sense, doesn't it.

Once you have the meter reading, as I said, set the aperture and shutter where you want and shoot
02-13-2012, 03:21 AM   #18
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How manual is manual? Are several types of manual: focusing, metering (aperture), and attitude. Manual metering has been well-discussed above. Manual focusing has various tricks. I need all those tricks with my delaminating eyeballs. These tricks include:

* I use a katzeye-clone split-focus screen on my K20D. This helps with contrasty, well-lit subjects.
* The green hex of Focus Confirmation (FC) tells me when I'm sliding into and past focus.
* CIF (catch-in-focus) nails the focus for me. The centered subject comes into focus, and SNAP!
* With zone-focus aka hyperfocus, I set aperture and focus for a desired DOF range.
* Guesstimate or pace-off or carefully measure lens-to-subject distance.

What's manual attitude? Putting together Lowell's metering process, my focusing tricks, an eye for composition, and the knowledge that I'M SMARTER THAN THE CAMERA! Machine-assisted metering and focusing don't necessarily capture images as *I* want them to look.

One of my rants is that what we think we see, what we want to see, what the camera+lens sees, and what's really there (if anything) are not the same. With manual attitude, I set up the picture the way I want, decide what will be in or out of focus, whether to expose for highlight or shadow detail, what dynamic range I want, etc. Sometimes I don't want any help from the camera -- it shoud just do what it's told, like a nice dumb tool. Then *I* am responsible for the picture, just me, not the engineers who programmed the camera's algorithms.
02-14-2012, 03:36 PM   #19
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QuoteOriginally posted by reivax Quote
My understanding is that I would have to set my own shutter speed and my own aperture for every shot?
And ISO. Once those three have been set for a scene, the camera remembers them and you only have to change them if the scene gets brighter or darker.

For the first photo, there are more steps. In practise I find the steps are easy enough, but it's easy to forget one or all of them. (Especially ISO.) I pretty much have to go through a check-list in my head. It leads to a slower pace of photography. I can't do it if there are non-photographers around waiting. There's not much point me taking a manual lens on a group holiday. However, if I have the time, then taking the time is probably a good thing. Manual lenses are educational.

02-14-2012, 04:29 PM   #20
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QuoteOriginally posted by stevebrot Quote
With the K-r it is better to use M mode for metering (this is hidden deep in manual). Pentax applies a more appropriate exposure algorithm in that mode on the newer cameras. Av mode suffers from the same issues as my K10D...wild underexposure at apertures wider than about f/4 with most lenses.

One caution regarding stop-down metering and narrow apertures. There is a limit to meter sensitivity and a fully stopped down lens in moderately dim light may take the meter below its linear range. Although Pentax claims a lower sensitivity of EI(100) 1, my experience is that the real value is closer to EI(100) 2-2.5. Fortunately, with a dSLR, we get immediate feedback and can adjust the camera as needed.

One other exposure tip. You don't need to meter before every shot. My flow for stop-down metering with Pentax-K and Pentax-M lenses is to meter the subject, set the camera and shoot until either the subject or the light changes. Ditto for my M42 film cameras. There usually is little (no?) need to meter in real time. In fact, for certain subjects (stage lighting and birds in flight) you are better to put the meter for the subject illumination, put the camera in M mode and forget about it.


Steve
I don't have a K-r but with my K10D and K20D, I found more or less the same wild swings in exposure whether in Av or M mode. I started to test the assumption that Av mode is less accurate than shooting in M mode against a bare light bulb (for the reasons you've pointed out in the 2nd paragraph) but I've stopped because I thought it would be better to conduct the test on real shooting situations. Hopefully, I can conduct the test on a bright, sunny day and get back to you on this.

I agree with you about the limit to meter sensitivity being not as good as Pentax claims, but this limit affects not only stopped down metering of M42 lenses but any lens that displays F-- for the aperture value on the camera, in any mode. Without an aperture value, the camera will not compute the corresponding shutter speed beyond the meter sensitivity threshold.

I've never said that you need to meter for every shot but that the meter is always on in Av mode, adjusting the shutter speed as the lighting changes on the subject. Shooting in M mode, I would meter once and shoot because as you've correctly stated there is no need to meter for every shot but only when the lighting/subject changes (drastically), I usually forget to meter by pressing the green button. I know this is my own forgetfulness, stupidity (call it what you will), but metering in Av mode that don't require my active participation to meter as the lighting/subject changes, is a convenience worth pointing out.
02-14-2012, 08:51 PM   #21
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QuoteOriginally posted by excanonfd Quote
I don't have a K-r but with my K10D and K20D, I found more or less the same wild swings in exposure whether in Av or M mode.
Yes, that is what you would expect. Pentax changed the meter algorithms for M mode starting with the K-7. The change is real (I confirmed with the K-7) and is reflected in the user manuals for the newer cameras. M mode is recommended. Av mode is not.

As for meter sensitivity for M42 vs K-mount in stop-down mode...definitely...the same rules apply. F/16 at dusk and you are likely outside the linear range of the meter when the lens is stopped down.


Steve

(...may yet buy a K-5 to get better metering...)
02-14-2012, 08:59 PM   #22
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Great advice everyone. I finally got the lens today. Been testing it out and I noticed two things:

1) For being such an old lens, it takes great pictures. It is definitely sharper than my DA zoom lenses. Might be the new lens smell, but it seems to.
2) I am terrible at manual focus. Gonna need some practice, practice, practice.

One more thing I noticed. On the m42 lens, there is a little (not sure what to call it) switch/button that allows me to slide to auto/man. I'm assuming this controls aperture? I messed around with it, and unless I missed something, I can only control the aperture when it is set to man. Is this correct? Thanks.
02-14-2012, 10:44 PM   #23
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QuoteOriginally posted by reivax Quote
On the m42 lens, there is a little (not sure what to call it) switch/button that allows me to slide to auto/man. I'm assuming this controls aperture? I messed around with it, and unless I missed something, I can only control the aperture when it is set to man. Is this correct?
Yes...that is the only way you can stop the lens down when adapted to K-mount. You may note a small silver pin on the back of the lens? That is the "Auto" aperture actuator for when the lens is mounted to a M42 body. The body has a "flipper" that flips up against the pin to stop down the lens just before the shutter opens. Your K-mount camera body lacks the flipper so you move the lever to the M (manual) position to allow full manual aperture operation.

This and a lot more were discussed on this recent thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/175186-underst...42-lenses.html


Steve

02-14-2012, 11:59 PM   #24
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QuoteOriginally posted by stevebrot Quote
Yes, that is what you would expect. Pentax changed the meter algorithms for M mode starting with the K-7. The change is real (I confirmed with the K-7) and is reflected in the user manuals for the newer cameras. M mode is recommended. Av mode is not.

As for meter sensitivity for M42 vs K-mount in stop-down mode...definitely...the same rules apply. F/16 at dusk and you are likely outside the linear range of the meter when the lens is stopped down.


Steve

(...may yet buy a K-5 to get better metering...)
My upgrade path is limited to a K-5 seeing as how the K-01 is no longer in my sight due to it's lack of a viewfinder. So many here talk about K-01's innovative design but for the life of me, I can't see how innovative it is from my first P&S camera (I had a viewfinder on mine, for heaven's sake!): Steves Digicams - Panasonic Lumix DMC-FZ1 - User Review Oops, wrong place to rant.
02-15-2012, 10:44 PM   #25
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QuoteOriginally posted by excanonfd Quote
My upgrade path is limited to a K-5 seeing as how the K-01 is no longer in my sight due to it's lack of a viewfinder.
...ditto...
02-16-2012, 12:37 AM   #26
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Manual enough to teach you how to use your camera. Do youself a favor and buy an all manual (NOT A) lens. Even if you do eventually sell it and upgrade.

Honestly, the best thing I did before buying the FA 50 was own the K 55, which was completely manual (and didn't green button meter correctly). So I had to actually learn how to set things myself. Yes, I was often frustrated, but I learned things. I'm much better off now, even if my lenses will automatically select settings themselves. Computers are never as smart as you, it is best to know when to correct them! And I often use the FA 50 in manual focus mode... because auto-focus is not always better than a human.
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