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04-23-2015, 09:49 AM   #1
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Pentax's MF SLR Metering Pattern: Just Centerweighted?

I'm reading through some old literature on the Pentax manual focus SLRs of the 70s and 80s -- specifically the KX, LX, and MX -- all of which have a "centerweighted" metering pattern. I've looked for more particulars on this, but haven't been able to find any. I just read through an LX user's manual, and the only place they mentioned the metering pattern was at the end of the manual in the Specifications section. So I'm wondering if anybody can add anything to this. For example, Canon's A-series cameras used what Canon called a "bottom centerweighted" pattern. It gives some bias to the lower portion of the landscape framed image, the reason being that for a high percentage of the photos, people will be standing outdoors and the sky will be in the frame. By adding weighting to the bottom of the frame, it is reducing the possibility of under-exposure caused by too bright of a sky. In practice, Canon's BCW pattern pretty much sucks because it isn't BCW enough, IMHO.

So I'm wondering if Pentax's centerweighted pattern is just a straight center weighting or if it has a particular sort of emphasis, such as Nikon's famed 60/40 pattern, which has historically worked very well (60% of the weighting occurs inside of a circle visible in the camera's viewfinder and 40% of the weighting occurs for that portion of the image outside the circle). Anybody here know? Thanks in advance.

04-23-2015, 10:29 AM   #2
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QuoteOriginally posted by cooltouch Quote
So I'm wondering if Pentax's centerweighted pattern is just a straight center weighting or if it has a particular sort of emphasis, such as Nikon's famed 60/40 pattern, which has
If they did, they did not make any marketing claims. IIRC, some of the magazine reviews would include metering pattern. Perhaps a trip to the local library would yield what you are wanting to know.


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04-23-2015, 10:31 AM - 2 Likes   #3
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It's easier to find info on the LX than the others.

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Pentax LX - How does its metering works
04-23-2015, 10:39 AM   #4
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Thanks, Boris. That one is a very strongly centerweighted pattern, which is good, IMO. It looks like approximately 75% of the metering occurs within the 50% perimeter (averaging 100% and 50% will give 75%). Which is stronger than Nikon's 60/40 and almost as strong as Nikon's F3's 80/20. Thanks, Boris, this is very good to know. I wonder if the MX and KX have similar patterns.

04-23-2015, 11:23 AM   #5
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Out of my experience LX and K2s have a stronger centerweight pattern, almost like a Canon partial, MX and KX have more or less the same pattern of a Nikon FM, KM, K1000 and Spotties are average metered but I prefer them to the A-1s.

The MX also have gallium cells, very sensitive to light and if move to the subject the Ieds react very rapidly.
04-23-2015, 12:18 PM   #6
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I remember that literature at that time (early eighties) always explained center weight to be asymetrical (less "sky" more "foreground"). And I remember very well, being a young student with plenty of free time, playing around with the Super A (Super Program in the US) and verifying exactly this behaviour. If you targeted a landscape for example, you would get completely different exposure values if you held the camera bottom up. Thus I proved the theory written in the books.

The fact that center weight did not cover the full width of the image helped to get correct exposure in portrait mode, The left and right borders of the viewfinder do not contribute much to metering, hence enabling proper exposure of the sky in portrait mode.
04-23-2015, 06:11 PM   #7
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Thanks for the additional info, guys. This helps a lot. You know, it just dawned on me that I should be able to figure out meter sensitivity for myself. I own an A-1, and several Pentaxes -- a KX, K2, KM, and a few Spotmatics -- I kinda got carried away recently with buying MF Pentax gear. I also own an MV, but it doesn't count, besides, it's for sale. Pentax's equivalent to the Nikon EM and Canon AV-1 -- I think -- maybe the T-50 sans motor.

Anyway, UMC's test, validating the Pentax Super A's metering pattern is what gave me the basic idea. Now, the A-1 was marketed as having a bottom-centerweighted metering pattern (common to all A-series cameras), but unlike UMC's Super A, the metering sensitivity did not fall off toward the corners or edges. So if an extraneous light source made it into the frame, even on the very corner, it could cause the entire photo to be underexposed. It gave me fits because of this. Rather than learn to live with it, I just bought another camera -- an FTb, which uses Canon's 12% partial metering, which to me was just so much better. But I want to confirm my recollections about corner and edge sensitivity.

I've owned a KX for years, and picked up a Spotmatic SP with 50/1.4 Super Tak for next to nothing a few years ago. More recently I've added the aforementioned K2, KM, and a couple more Spotmatics, including an F, to the stable. So I'm gonna see if I can duplicate Cuthbert's claims regarding these cameras. Honestly, I've used both the KX and SP just a few times, and when I used them, there were no unusually lit scenes to fool their meters, so I haven't yet developed a feel for the way they meter.

I don't have an FM right now, but I do have an FE and it uses the same metering pattern. So I can compare the KX to the FE. And you mention that the K2's pattern is tighter, which makes sense since it has an Aperture Priority mode. Nikon did the same thing with the F3, reasoning I guess that if a photographer was going to use the A mode, the metering pattern had better be tighter. So Nikon went with an 80/20 pattern on the F3 compared to the 60/40 pattern it used in just about every other camera at the time.When I bought my first F3, I was a bit leery about using it on the A setting, but I decided to try it out -- shooting slide film, no less. And every photo came out perfectly exposed. I finally got to where I'd put it on "A" and not worry anymore about the outcome. I still have an F3, so I'll compare the way it meters a scene to the way the K2 does. This will be helpful. And if the KM and Spotties are just straight averaging, I can compare them with my Bronica ETRSi or Pentax 6x7. I have metering heads for both cameras and as far as I've been able to determine they have just a straight averaging pattern.

Well, this ought to be very interesting. I think I'll report back my findings in a separate thread.

Last edited by cooltouch; 04-23-2015 at 06:41 PM.
04-24-2015, 06:33 AM - 1 Like   #8
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Cooltouch, you're a lucky man because today I receive an interesting book about the ME Super and in one of the first page there's an image of the metering pattern that I assume is good for all the M bodies: as you can see it's centered but not symmetric like the Canon AE screen, for instance, actually it appears to be a quite sophisticated shape engineered to be able to work well for portraits, landscapes etc...please appreciate the stretched area on the horizon line.

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04-24-2015, 06:58 AM   #9
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QuoteOriginally posted by ChrisPlatt Quote
Sophisticated metering patterns are useful for fully automatic exposure.
Fortunately manual cameras, or AE cameras with exposure memory lock
are not hard to use even in tricky lighting regardless of meter pattern.
Simply get in close to take your reading. If that's impossible or impractical
use substitute metering; take a reading off a similarly lit object closer by.

Chris
I think it's a little difficult to get close to the subject when you have something like this:



Nevertheless this shot taken with a A-1 is well exposed because as cooltouch explained it's button metered, but I think the Pentax M pattern more flexible because it appears to be a horizon pattern overimposed to a spot one.

QuoteOriginally posted by boriscleto Quote
It's easier to find info on the LX than the others.

Pentax LX



Pentax LX - How does its metering works
I assume this pattern is not much different from the K2DMD, which works very well in difficult conditions such as the below pic: a white marble torso in a windowpane shot in nightime at f2.8 and 1/30s. With a less sophisticated pattern such a picture wouldn't be possible.


Last edited by Cuthbert; 04-24-2015 at 07:04 AM.
04-24-2015, 09:11 AM   #10
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QuoteOriginally posted by cooltouch Quote
Honestly, I've used both the KX and SP just a few times, and when I used them, there were no unusually lit scenes to fool their meters, so I haven't yet developed a feel for the way they meter.
I can attest to all the equipment you listed except for Bronica ETRSi or Pentax 6x7. Obviously people have used these unsophisticated meters for those decades, and some even less sophisticated before then, and got good exposures even if they had to resort to braketing. Heck my Arcus C-3 Match-matic - with an accessory meter, limited shutter and aperture selections, had instructions on using the extremely narrow latitude chromes of the day with filters and flash and people got good exposures even then . . .

---------- Post added 04-24-15 at 12:13 PM ----------

QuoteOriginally posted by Cuthbert Quote
I assume this pattern is not much different from the K2DMD, which works very well in difficult conditions such as the below pic: a white marble torso in a windowpane shot in nightime at f2.8 and 1/30s. With a less sophisticated pattern such a picture wouldn't be possible.
In the case of the white marble dominating most of the frame, I would have expected the white to be gray and the frame to be a little underexposed?
04-24-2015, 09:59 AM   #11
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QuoteOriginally posted by LesDMess Quote

In the case of the white marble dominating most of the frame, I would have expected the white to be gray and the frame to be a little underexposed?
Do you think the pic is overexposed? Please take into account I used Neopan, not BW400CN.
04-24-2015, 10:07 AM   #12
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QuoteOriginally posted by Cuthbert Quote
Do you think the pic is overexposed? Please take into account I used Neopan, not BW400CN.
I think it has a well balanced exposure but would have expected it to be underexposed if you had not compensated for it in meter or in post. Only you will be able to tell from the negative.
04-24-2015, 10:58 AM   #13
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QuoteOriginally posted by LesDMess Quote
I think it has a well balanced exposure but would have expected it to be underexposed if you had not compensated for it in meter or in post. Only you will be able to tell from the negative.
on

mmm to be honest I don't think I compensated...just pointed the K2DMD at the subject and shot.
04-24-2015, 03:09 PM   #14
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Interesting. I agree with LessDMess on this one. I like to keep in mind that a camera's meter is going to interpret the subject as being 18% gray, so on that basis I would say your shot of the statue is somewhat overexposed. The camera doesn't know it's white marble. It doesn't even know it's white. It will see all that is in the metering area as 18% gray and expose accordingly. This is why you often need to overexpose when you're shooting predominant snow scenes, for example. It seems counter-intuitive, but if you don't, the snow comes out looking like mud.

Nonetheless, to me, the above scene is just slightly overexposed. There's burn-through in the face and the right shoulder/breast area. If I were to bump down the exposure just a touch, more texture would show up in the marble, which is my preference.
04-24-2015, 10:46 PM   #15
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QuoteOriginally posted by Cuthbert Quote
Cooltouch, you're a lucky man because today I receive an interesting book about the ME Super and in one of the first page there's an image of the metering pattern that I assume is good for all the M bodies: as you can see it's centered but not symmetric like the Canon AE screen, for instance, actually it appears to be a quite sophisticated shape engineered to be able to work well for portraits, landscapes etc...please appreciate the stretched area on the horizon line.
Yep the ME & MX have the same meter sensitivity pattern.

The K Series are different.

K2's & KX are center weighted but have different patterns and the KM & K1000 use averaging.

Phil.
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