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03-08-2009, 07:37 AM   #1
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multi-segment metering and M lenses

Pentax cameras are set up so non-A lens do not use multi-segment metering.

I've read this is because max/min f-stop & Data info is not available to the camera for such lenses. But why should this matter? If I mount an m42 lens and fool my camera into thinking an "A" lens is attached does multi-segment metering give bad results?

Initial experiments don't indicate a problem; am I missing something?

Also, why use multi-segment metering at all? Spot metering, locking, then re-composing sounds logically best to me. Or maybe multi-segment is best when one doesn't have the time to spot meter & recompose?

All comments about metering methods & scenerios are welcome.

Iowa Dave

03-08-2009, 08:43 AM   #2
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QuoteOriginally posted by newarts Quote
Pentax cameras are set up so non-A lens do not use multi-segment metering.

I've read this is because max/min f-stop & Data info is not available to the camera for such lenses. But why should this matter? If I mount an m42 lens and fool my camera into thinking an "A" lens is attached does multi-segment metering give bad results?

Initial experiments don't indicate a problem; am I missing something?

Also, why use multi-segment metering at all? Spot metering, locking, then re-composing sounds logically best to me. Or maybe multi-segment is best when one doesn't have the time to spot meter & recompose?

All comments about metering methods & scenerios are welcome.

Iowa Dave
You mean spot meter, calculate out how far off Zone V the metered area is, set the exposure to compensate for that, then compose and shoot, no?

Spot metering, to me seems a little foolish to even include on a DSLR since it is so easy to check exposure immediately after taking the picture, and it's not like as if spot metering lends itself to rapid shooting anyway.
I do always use a spot meter when shooting with my 4x5, as the metering method does, in my mind complement the whole process of large format photography.
Having a Zone VI modified Pentax Digital Spot Meter for metering is kind of cool, too.

The best spot metering approach I've read about, and the one I use to tremendous metering accuracy with large format is to meter off the clouds (obviously, this is a scenic metering method that requires some clouds in the sky) and then set the exposure 3 stops higher to take them to Zone VIII.
I read about this metering method in a Zone VI newsletter many years ago.

I suspect that doing something similar with a DSLR and using exposure compensation to increase the exposure the required amount would make this a fairly fast and painless method of metering.
It doesn't change my view that it is a pretty redundant feature though.

I get significantly more exposure failures when in multi segment metering than I do with center weighted, so I tend to use center weighted averaging. I suspect that 35 or so years of using that style of meter has made me comfortable with how it looks at a scene.
03-08-2009, 09:32 AM   #3
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QuoteOriginally posted by Wheatfield Quote
You mean spot meter, calculate out how far off Zone V the metered area is, set the exposure to compensate for that, then compose and shoot, no?...
I mean spot (or center-weight ) meter on what you want to be correctly exposed (is that what Zone V means?) then push the AE-L button, compose, focus & shoot.

So yes, I guess that's what I'm suggesting, but no calculation would normally be required if the spot (maybe center weighted) location metered is appropriately chosen.

Also, can you see any reason why non-A lenses should require a different metering strategy from A lenses?

Dave
03-08-2009, 12:15 PM   #4
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Exposure differences

I believe there was an explanation of this in a thread a while back - a difference between using a 'light value' or an 'f-stop' as the proportional difference between lens aperture stops if I recall.

With the instant exposure review and in-camera compensation I'd think you could manage either way - in a practical sense.

H2

03-08-2009, 12:27 PM   #5
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QuoteOriginally posted by newarts Quote
....meter on what you want to be correctly exposed (is that what Zone V means?) then push the AE-L button, compose, focus & shoot.
.....

Also, can you see any reason why non-A lenses should require a different metering strategy from A lenses?

Dave
Maybe I see now. Non-A lenses can't work in AUTO PIC mode because the lens can't be stopped down correctly. I forgot about trying to do things automatically.

Dave
03-08-2009, 12:56 PM   #6
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QuoteOriginally posted by Wheatfield Quote

Spot metering, to me seems a little foolish to even include on a DSLR since it is so easy to check exposure immediately after taking the picture, and it's not like as if spot metering lends itself to rapid shooting anyway.
I do always use a spot meter when shooting with my 4x5, as the metering method does, in my mind complement the whole process of large format photography.
Having a Zone VI modified Pentax Digital Spot Meter for metering is kind of cool, too.

One use for spot metering I use all the time is to determine the dynamic range when I'm bracketing shots for HDR.

I'm probably wrong, but I'm sure giving Photomatix Pro just enough data leads to a more 'natural' tone mapped print. All the black pixels and burnt out to white pixels always seem to be lurking in the file. Blacks give that muddy look and white seem to lead to halos.

Chris
03-08-2009, 04:29 PM   #7
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QuoteOriginally posted by Wheatfield Quote
Spot metering, to me seems a little foolish to even include on a DSLR since it is so easy to check exposure immediately after taking the picture, and it's not like as if spot metering lends itself to rapid shooting anyway.
Now don't get me started on this, but this is an area where I completely disagree. I shoot a lot of wildlife, which is in and out of shadows.

THis is one area where spot metering is a necessity, because your subject may not have the patience to wait for you to check your histogram and re-shoot. This is especially true of birds in flight. you only have one shot at the subject, and wht would you want to risk loosing it due to matrix metering that is paying more attention to the background
03-08-2009, 04:34 PM   #8
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QuoteOriginally posted by newarts Quote
I mean spot (or center-weight ) meter on what you want to be correctly exposed (is that what Zone V means?) then push the AE-L button, compose, focus & shoot.
That would be OK if that's how spot metering worked, but it isn't. Spot metering tries to make whatever you point at look like 18% grey (that's more or less what Zone V means). If you spot meter off a white object, it comes out medium grey, and everything else in the scene darker still - which is to say, the picture is badly underexposed. If you spot meter off a black object, it comes out medium grey, with everything else lighter - which is to say, the picture os badly overexposed. So when using spot metering, you have to either meter off something that really *is* approximately 18% grey in value, or else figure out how much compensation to dial in.

03-08-2009, 04:44 PM   #9
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QuoteOriginally posted by Me:
I mean spot (or center-weight ) meter on what you want to be correctly exposed (is that what Zone V means?) then push the AE-L button, compose, focus & shoot.
QuoteOriginally posted by Marc Sabatella Quote
That would be OK if that's how spot metering worked, but it isn't. Spot metering tries to make whatever you point at look like 18% grey (that's more or less what Zone V means). If you spot meter off a white object, it comes out medium grey, and everything else in the scene darker still - which is to say, the picture is badly underexposed. If you spot meter off a black object, it comes out medium grey, with everything else lighter - which is to say, the picture os badly overexposed. So when using spot metering, you have to either meter off something that really *is* approximately 18% grey in value, or else figure out how much compensation to dial in.
Exactly. That's what I meant by "meter on what you want to be correctly exposed", ie. 18%. like a face, my hand, the concrete, etc. It seems to me that maybe I can make that decision better than the camera much of the time.
03-08-2009, 08:27 PM   #10
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QuoteOriginally posted by newarts Quote
Exactly. That's what I meant by "meter on what you want to be correctly exposed", ie. 18%. like a face, my hand, the concrete, etc. It seems to me that maybe I can make that decision better than the camera much of the time.
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03-09-2009, 01:37 PM   #11
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QuoteOriginally posted by newarts Quote
Exactly. That's what I meant by "meter on what you want to be correctly exposed", ie. 18%. like a face, my hand, the concrete, etc.
Gotcha. Yes, as long as you realize you can't point at just *anything* to meter off - it's got to be something close to 18% gray, or else you'll have to dial in compensation.

FWIW, I use center weighted metering, but I use it more or less the way one might use spot metering. I mentally divide the scene into "light" and "shadow" areas, choose which I want exposed well, and point the camera directly into an area that's in the light or an area that's in the shadow. Not necessarily areas I'm planning on shoot - the ground by my feet is a very common target for me. Using center weighted metering means I don't have to try to find a specific object that is 18% - most scenes will *average* close enough to 18% if you limit consideration to mostly just the shadows or most just the lights. And to the extent that the light area still influences the exposure even though I'm pointing in the the shadow (or vice versa), I figure that's good - it will keep my highlights from completely blowing out, or my shadows from being unreadably dark. In fact, sometimes, I'll meter by finding a nice dividing line between light and shadow, hitting the Green button there, then pointing into one area then the other and checking to see how much above and below they are, and then nudging the exposure in one direction or the other.
03-09-2009, 01:45 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
FWIW, I use center weighted metering, but I use it more or less the way one might use spot metering. I mentally divide the scene into "light" and "shadow" areas, choose which I want exposed well, and point the camera directly into an area that's in the light or an area that's in the shadow. Not necessarily areas I'm planning on shoot - the ground by my feet is a very common target for me. Using center weighted metering means I don't have to try to find a specific object that is 18% - most scenes will *average* close enough to 18% if you limit consideration to mostly just the shadows or most just the lights. And to the extent that the light area still influences the exposure even though I'm pointing in the the shadow (or vice versa), I figure that's good - it will keep my highlights from completely blowing out, or my shadows from being unreadably dark. In fact, sometimes, I'll meter by finding a nice dividing line between light and shadow, hitting the Green button there, then pointing into one area then the other and checking to see how much above and below they are, and then nudging the exposure in one direction or the other.
It sounds like the best strategy to me; it adds the photographer's intelligence and experience to that of the camera; plus the more you do it the better you'll get.

Dave
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