Archive 2007 · Pentax K10D Metering Anomoly

Gonzalo Tudela
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p.1 #1 · p.1 #1 · Pentax K10D Metering Anomoly

Hey guys, I have a student here who's having a problem with his K10D...

Here's what's up... When metering with a zoom lens, the gray cards read consistently from zoomed out to zoomed in, but the blacks have a 3 stop difference (will go from -3 stops to 0 on the metering levels from zoomed out fully to zoomed in fully) and the whites have a 1 stop difference (+2 to +3 from zoomed out fully to zoomed in fully)... The lens he is using is a Sigma 18-200 F3.5-6.7... I would test it on another lens but the problem is that his other lens is a 50mm 1.4 Prime lens...

Let me know if you guys know of anyone that's having these issues and or if they've found a way to fix it up!

Thanks,
Gonzo

Jul 16, 2007 at 11:06 PM

HerbChong
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p.1 #2 · p.1 #2 · Pentax K10D Metering Anomoly

is the card filling the viewfinder in CW or multi-segment metering modes or is the metering spot in SP mode entirely filled by the card?

Herb...

Jul 17, 2007 at 09:47 AM

Gonzalo Tudela
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p.1 #3 · p.1 #3 · Pentax K10D Metering Anomoly

It is happening with all three metering modes, and yes the card is filling the viewfinder in all tests done...

It's really odd, happens really badly with black objects, and not sorta bad with white objects.... It works perfect on a gray card....

Jul 17, 2007 at 11:22 AM

John Black
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p.1 #4 · p.1 #4 · Pentax K10D Metering Anomoly

Cameras meter for around 17% gray, filling the viewfinder with pure white or pure black means the camera will under-expose a white and over-expose a black --- all in an effort to achieve ~17% gray. This is a very simplified explanation, the nuances are different for spot, center and evaluative metering. This is usually discussed in the owners manual.

Jul 17, 2007 at 11:27 AM

Gonzalo Tudela
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p.1 #5 · p.1 #5 · Pentax K10D Metering Anomoly

ok, maybe I wasn't clear....

There is a 3 stop difference from ZOOMED OUT to ZOOMED IN on the same black object
There is no difference from ZOOMED OUT to ZOOMED IN on the same gray card
There is a 1 stop difference from ZOOMED OUT to ZOOMED IN on the same white object

and yes, the viewfinder was filled the whole time...

Jul 17, 2007 at 12:10 PM

mskad
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p.1 #6 · p.1 #6 · Pentax K10D Metering Anomoly

Gonzalo Tudela wrote:
ok, maybe I wasn't clear....

There is a 3 stop difference from ZOOMED OUT to ZOOMED IN on the same black object
There is no difference from ZOOMED OUT to ZOOMED IN on the same gray card
There is a 1 stop difference from ZOOMED OUT to ZOOMED IN on the same white object

and yes, the viewfinder was filled the whole time...

... And of course you took in account the fact that your zoom lens is of variable aperture kind.

Jul 17, 2007 at 01:10 PM

Gonzalo Tudela
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p.1 #7 · p.1 #7 · Pentax K10D Metering Anomoly

Tests were all done at F8

Jul 17, 2007 at 07:38 PM

HerbChong
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p.1 #8 · p.1 #8 · Pentax K10D Metering Anomoly

you did the same test with a different brand of camera with a somewhat similar lens?

Herb...

Jul 17, 2007 at 09:36 PM

Gonzalo Tudela
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p.1 #9 · p.1 #9 · Pentax K10D Metering Anomoly

I used my Mark II N with my 70-200 and had no problems...

He's trying a few tests at a store with the brand new lens and his body... I'll let you guys know what's up

Jul 18, 2007 at 12:43 PM

wlachan
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p.1 #10 · p.1 #10 · Pentax K10D Metering Anomoly

I tested my DS with my only zoom DA10-17 and seem to have similar characteristic. But since it is a fisheye, I am a little uncertain. Could it be the black subject was so dark the EV exceed the metering range of the K10D?

Jul 18, 2007 at 01:59 PM

Gonzalo Tudela
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p.1 #11 · p.1 #11 · Pentax K10D Metering Anomoly

ya, it's just really weird...

like I was teaching him the zone system, and how you can place black objects with detail in zone III and white objects with detail in zone VII, and that you can use you're spot meter in camera to get all the info right away... But then when we found this, I was like "wow there nelly, somethin's up"

I'll be talking to Pentax this week and see if they know of this...

Jul 21, 2007 at 01:39 PM


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