[FHPhotographer]

The things you learn when you read the manual. Am I reading this correctly, that on the K20 the 16-segment Multi-segment metering (matrix) mode only works with Pentax lenses (p 98) ? Since "matrix" modes are generally the most sophisticated (notice I didn't say best) it's a shame if Pentax has made this a proprietary feature that can't be used on Sigma/Tamron etc.
I wonder if other makes do the same, and is this continued for the Kr and K5?
Brian

ADDITION:
Interesting responses, including assumptions about how Pentax operates, or what a statement in the Manual means , but this is exactly what the manual says specifically (p 98) "The center-weighted metering mode is automatically set even if you select the mutli-segment metering mode when using a lens other than a DA, D FA, FA J, FA, F or A lens..." Be that as it may, I've subsequently gone back and looked at several dozen "multi-segment" images taken with third-party lenses just to double check that I wasn't, in fact, shooting with center-weighted metering when I had the camera set to multi-segment, and the EXIF data (using the term "pattern" which I assume is the same as "matrix" or Pentax-specific multi-segment mode) shows that all the metering modes do work with third-party lenses. I now amend my OP to read "The things you learn when you read the manual may, or may not, be correct..."

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Last edited by FHPhotographer; 12-16-2010 at 12:36 AM.

[Class A]

I don't know the wording in the manual but it might be misleading. As a matter of fact, matrix metering works with third-party lenses as well.

It doesn't work on non-A lenses which require stop down metering.

[sterretje]

Nothing states that it is proprietary; that's your interpretation of the text in the memo.

Pentax simply does not refer to 3rd party lenses and only to their own lineup. The list would be too long and why would they; they like to sell lenses as well.

The same memo appears in the K-5 manual on page 117 and in the K10D manual on page 142; those are just two that I checked.

[Lowell Goudge]

There are two distinct issues here, the first is yes, each camera manufacturer's matrix metering is proprietaty, and yes it works with all lenses that have automatic aperture.

The reason it is propriatery is that each manufacturer uses different logic in interpreting the scenes, although until the K7 with 77 metering segments, the older pentax logic which uses 11 segments is somewhat lagging in the industry.

The issues involve really how the highlights and lowlights are interpreted, within the scene, in determining the optimum metering.

At one time, Nikon had claimed up to 5000 unique lighting combinations were possible within the metering, and the camera would evaluate the pattern against those to determine metering.

What I have never bothered to learn is why the metering needs to know the aperture range of the lens, or aperture setting as part of the evaluation process

[Class A]

What I have never bothered to learn is why the metering needs to know the aperture range of the lens, or aperture setting as part of the evaluation process

Perhaps the exposure matrix has a native aperture, e.g. f/5.6 like the AF system, and will "black out" except for the centre spot if used with aperture like f/11.

But this is just speculation on my behalf.

P.S.: It's 16 segments, not 11.

[Boris]

Nothing proprietary here, really. The protocols of info transmission between the lens and the body are described in some detail on Boz's site. I believe that some of the 3rd party manufacturers (Tamron e.g.) have full integration with Pentax bodies. I don't know exactly - did they license the info or entered some other agreement with Pentax, but their 28-75/2.8 is as good as any native Pentax lens.

Now, for matrix metering to work, lens has to transmit certain information to the body. I am thinking that the actual aperture, the distance to the object as per AF status would be useful bits. Any lens that does so according to the Pentax protocols would be as good as native. Matrix metering appears to work with A lenses, such as A 50/1.2 which are not AF. So perhaps the AF data is used for flash photography or more advanced metering. I don't know for sure. But I can tell you that all 3rd party lenses, even very old Tamron 90/2.5 Adaptall with KA adaptall adapter exposed properly on my *istD, K10D and K-7 in matrix metering mode.

[rawr]

My impression was that matrix exposure metering did only work with Pentax lenses. Non-Pentax lenses got centre-weighted metering by default, even if the menu setting said matrix.

That's also been my impression in the field too. For example I recently shot an annual fair in my town with my Tamron 17-50 that I had shot last year with my DAL 18-55. The kit lens nailed the exposure much more competently than the Tamron did - in particular metering backlit scenes better. I had to do quite a bit of PP on images this time around to bring people's faces out of shadows etc on scenes that I didn't need to do last year. Even though I had the metering set to matrix, the exposure pattern of the images taken with the Tamron certainly matched up with what I expected centre-weighted averaging to look like.

[Class A]

The kit lens nailed the exposure much more competently than the Tamron did - in particular metering backlit scenes better. I had to do quite a bit of PP on images this time around to bring people's faces out of shadows etc on scenes that I didn't need to do last year.

The fact that the camera "underexposed" because of a bright background is in indication that matrix metering was used. If it had been spot-metering, one would expect the exposure to be correct for the people and the background to be blown out. Unless you had the centre of the frame pointed to bright spots, that is.

Anyhow, your theory is easy to test. You might want to confirm your hunch. I have a lot of Sigma lenses and had no indication whatsoever that my K100D uses spot-metering for them.

When I use manual lenses with stop-down metering, on the other hand, the metering is definitely spot-metering only. EDIT: The other (and default) mode is "Centre-weighted". Thanks to Pablom and NaClH2O for pointing it out.

[Pablom]

When I use manual lenses with stop-down metering, on the other hand, the metering is definitely spot-metering only.

from my experience center weighted is also possible with manual lenses, in fact it is the default setting

[NaClH2O]

The fact that the camera "underexposed" because of a bright background is in indication that matrix metering was used. If it had been spot-metering, one would expect the exposure to be correct for the people and the background to be blown out. Unless you had the centre of the frame pointed to bright spots, that is.

Anyhow, your theory is easy to test. You might want to confirm your hunch. I have a lot of Sigma lenses and had no indication whatsoever that my K100D uses spot-metering for them.

When I use manual lenses with stop-down metering, on the other hand, the metering is definitely spot-metering only.

Class A, are you sure of this? I can get spot and center weighted metering on all my K lenses. Can't get matrix, but center weighted works quite well. In fact the only time I use spot metering with my K lenses is if I'm shoot back lit scenes or for unusually lit scenes. For instance outdoor summer concerts where the performers are on a shaded stage and I'm in the bright sun. I've been able to do this with the DS, K10D and now my K20D.

NaCl(maybe I'm special, but I don't think so)H2O

[rawr]

The fact that the camera "underexposed" because of a bright background is in indication that matrix metering was used. If it had been spot-metering, one would expect the exposure to be correct for the people and the background to be blown out. Unless you had the centre of the frame pointed to bright spots, that is.

That's not how it works. The default exposure scheme for non-Pentax lenses is centre-weighted averaging, not spot metering. Spot metering is very different from centre-weighted and is not really part of the discussion. As the K200D manual explains it, center weighted averaging " measures the entire viewfinder with an emphasis on the center" - ie it attempts to calculate an exposure average that would work across the whole frame, but heavily weighted to the centre. And moreover, "this mode does not automatically compensate for backlit scenes".

Multi-segment metering does attempt to be more intelligent, and recognise the structure of a scene and the varied lighting within it. It is usually pretty good at for example detecting shadowed areas against a bright background like the sky, and compensating accordingly.

Unlike multi-segment metering, centre weighted averaging is not intelligent at all and applies a fixed sensitivity pattern across the frame. Hence there can be a greater probability of shadows appearing in backlit scenes, especially if the image subject does not completely fill the centre of the frame.

If however I was using spot metering, rather than centre-weighted averaging, then your point would be valid, but centre-weighted averaging does not equal spot.

[RBellavance]

My impression was that matrix exposure metering did only work with Pentax lenses. Non-Pentax lenses got centre-weighted metering by default, even if the menu setting said matrix.

That's not how it works. The default exposure scheme for non-Pentax lenses is centre-weighted averaging, not spot metering.

This is simply not true. Multi-segment metering is available with any lens having an "A" setting, even 3rd-party ones. When matrix is unavailable, the "center-weighted" icon lights up in the viewfinder even if the metering mode selection lever is set to "matrix".

[paperbag846]

This is simply not true. Multi-segment metering is available with any lens having an "A" setting, even 3rd-party ones.

I believe the answer is that matrix metering requires maximum aperture information to work. A lenses transmit this information, while pre-A lenses are unable to transmit any aperture information to the body.

I could be wrong.

[Class A]

from my experience center weighted is also possible with manual lenses, in fact it is the default setting

True, I forgot that centre-weighted is also possible and indeed the default mode.

I can get spot and center weighted metering on all my K lenses.

Yes, mea culpa.

That's not how it works.

Well it is for the mode (spot metering) I assumed.

Multi-segment metering does attempt to be more intelligent, and recognise the structure of a scene and the varied lighting within it. It is usually pretty good at for example detecting shadowed areas against a bright background like the sky, and compensating accordingly.

On my K100D multi-segment metering will almost never cause largish highlights to be blown. In a backlit scene this means that the metering will attempt to preserve the bright background and won't be able to lift the exposure up to lighten up the dark foreground.

Maybe that is different with newer cameras like the K-7 which have more than the 16 exposure segments of the K100D.

BTW, I checked the K100D & K-5 manuals and w.r.t. matrix metering they refer to lens types such as "DA", "D FA", etc. rather than saying "Pentax lenses". Third-party lenses also fall into these lens categories, even if their designation doesn't say so. My Sigma 70/2.8 MACRO DG EX lens, for instance, is -- for all intents and purposes -- an "FA J" (like "FA" but without an aperture ring) lens to the camera. Hence all "FA J" features are supported, including matrix metering.

[Wheatfield]

The things you learn when you read the manual. Am I reading this correctly, that on the K20 the 16-segment Multi-segment metering (matrix) mode only works with Pentax lenses (p 98) ? Since "matrix" modes are generally the most sophisticated (notice I didn't say best) it's a shame if Pentax has made this a proprietary feature that can't be used on Sigma/Tamron etc.
I wonder if other makes do the same, and is this continued for the Kr and K5?
Brian

Pentax can't, and won't take responsibility for how non Pentax equipment will operate, so they don't acknowledge the existence of no Pentax equipment in their literature.