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M9 metering pattern


Lindolfi

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Bert--Very nicely done!

 

A request: Consider trying the same thing with a wide-angle or ultra-wide as well, just as a comparison.

 

In the M8 introduction, my class was told that the camera "becomes more center-weighted average" with longer focal lengths, and "becomes more like a spot meter" with shorter focal lengths.

 

Just curious whether the M9 shares this tendency to any great degree.

 

It's good to see someone with your technical accuracy taking on the meter pattern! :)

Edited by ho_co
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In the M8 introduction, my class was told that the camera "becomes more center-weighted average" with longer focal lengths, and "becomes more like a spot meter" with shorter focal lengths.

 

Just curious whether the M9 shares this tendency to any great degree.

 

That is not the case in the M9: I've tested a 21/2.8 at f/5.6 and it produced a similar result as with the 90/4 at f/8.

 

So that's nice: you only have to visualize one area during measuring, independent of focal length.

 

It is obvious that in absolute measurement angle, the longer focal length covers a smaller angle in the outside world than a wide angle lens. So if you want to use your M9 as a 5 degree spotmeter, mount a 135mm lens and nothing shorter.

Edited by Lindolfi
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Sounds as if Stefan Daniel was right when he said the M9's metering pattern was similar to that of the M6!

 

Sounds like a noticeable improvement from the M8 as well. The M8 introduction class specified that the spot effect was stronger with wide angles, and reduced with longer focal lengths: just the opposite of your description with the M9. (Speaking of metering pattern, not lens field of view.)

 

Thanks for your graphic effort, Bert. ;)

 

Seems to me that a chart like yours would be helpful either in the M9 manual or in the M9 FAQ here on the forum.

Edited by ho_co
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interesting how the sensitivity leaks to the bottom and not to the top but seems fairly even left to right.

steve

 

Imagine shining a cone-shaped beam of light on a wall at an angle upward. You will get a deformed ellipse that spreads out more above the center of the beam than below. Now if this cone-shaped beam is analogous to the cone-shaped sensitivity of the light meter in the bottom of the M9, it is understandable that if it is aimed at the middle of the focal plane, there is more sensitivity above the middle of the focal plane, than below it.

Since later on the image is rotated to be viewed by us, there is more sensitivity below the middle of the image, but it's extension is limited by the blackness of the top shutter element (bottom of the image).

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A request: Consider trying the same thing with a wide-angle or ultra-wide as well, just as a comparison.

 

In the M8 introduction, my class was told that the camera "becomes more center-weighted average" with longer focal lengths, and "becomes more like a spot meter" with shorter focal lengths.

 

Just curious whether the M9 shares this tendency to any great degree.

 

People – even people who should know better – automatically think SLR though this is not applicable to any M camera. A M, like any well-regulated English household, has an Upstairs and a Downstairs, and only the most formal connections between them. And metering is done in the Servants' Quarters.

 

In his Leica M Compendium, Handbook of the Leica M system (Hove, 1994) Jonathan Eastland, who surely knows better when he stops to think, declares (p. 130) that

 

"The diameter of the measuring field is equal to 2/3 of the short side of the bright-line frame in use. – This is a useful piece of information because in practice it means that the photographer can accurately measure very small areas of the object to be photographed using the preselector lever. – For example, when using wide-angle lenses, the measuring field of the meter appears larger. [ ... ] By flicking the preselector lever to bring up the 90mm bright-line frame, particular areas of the scene can be measured and interpolated."

 

So the otherwise estimable Mr Eastland thinks that by changing the frames upstairs, he can change the metering angle downstairs, without changing lenses! Good try.

 

And I do suspect that this kind of thinking lies behind the statement that metering angles are different relative to the picture angle with wide and long lenses. Mr Eastland I presume cut his teeth on SLR cameras with TTL metering (he mentions Nikon). Today's amateur photographers, and future pros, cut their teeth on cell phones, holding their humonguous DSLR cameras with long zooms in front of them on outstretched arms. I wonder what other strange behaviours this will lead to.

 

Anyone who launches a DSLR that you can make phone calls from, has a winner.

 

LB

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Indeed Lars, Jonathan Eastland was wrong there. The manual of the Leica M6 does show the measurement area correctly as scaling with the angle of view of the lens mounted and being constant in size relative to the correct framelines (not the one chosen with the preview lever), and thus keeping the coverage on the filmplane ("downstairs") the same.

 

I have superimposed the circle of the M6 from the manual onto my graph:

 

m9andm6sens.png

 

You can see the strong resemblance between the meters of the M6 and M9 as Stephan Daniel already pointed out.

My graph can easily be viewed in stops also: 0.5 is 1 stop lost, 0.25 two stops and 0.1 slightly more than three stops lost in sensitivity.

Edited by Lindolfi
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Correct me if i'm wrong, or if i missed something, but i think there is a misunderstanding of Eastland assertion.

He says "With a wide angle mounted", typically a 35 mm, you can preview the most active metering area for this lens by flicking the lever to show the 90 mm frame.

With any other lens, the metering area will vary in the same proportion : 2/3 of the height of the frame : so approximately for a 50 mm that would give an equivalent of a 135, and for a 28 something like a 50 mm frame.

But without touching any lever it's easy to imagine a center active metering spot of the correct size in the wiewfinder according to the lens mounted.

 

Anyhow you made a great job Indolfi

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Correct me if i'm wrong, or if i missed something, but i think there is a misunderstanding of Eastland assertion.

He says "With a wide angle mounted", typically a 35 mm, you can preview the most active metering area for this lens by flicking the lever to show the 90 mm frame.

With any other lens, the metering area will vary in the same proportion : 2/3 of the height of the frame : so approximately for a 50 mm that would give an equivalent of a 135, and for a 28 something like a 50 mm frame.

But without touching any lever it's easy to imagine a center active metering spot of the correct size in the wiewfinder according to the lens mounted.

 

Anyhow you made a great job Indolfi

See post #9

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Thanks Jaap.

 

It is however confirming my objection to the system: if you shoot in portrait mode, it will give different results if you turn the camera 90 degrees to the left or 90 degrees to the right...

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Thanks Jaap.

 

It is however confirming my objection to the system: if you shoot in portrait mode, it will give different results if you turn the camera 90 degrees to the left or 90 degrees to the right...

 

Just did a test: filling the left half of the image with black and the right half with white in portrait orientation and taking the same image after turning the camera 180 degrees, so that now black is right and white is left. (care was taken that the boundary between black and white was exactly through the middle of the image).

 

The black and white had a difference of 7 stops in brightness.

 

Result: same measurement of exposure time in the 1/3 stop accuracy the M9 offers in both portrait orientations.

 

So no reason to be consistent in how you turn the camera to portrait orientation: just use the meter as though it is rotation symmetric around the centre of the image.

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  • 5 years later...
  • 2 weeks later...

My metering patterin of my m9-p is more sensitive in the top half. It is frustrating but of of course i get around that. Is this possible???

 

Very often the top part of the frame has most of the light. It looks like my M-E will grab it and use it as exposure factor. As result the lower part is strongly underexposed.  To get it done properly, I let it measure the bottom part. Focus, compose, measure lower part, half-press the shutter button, recompose, take exposure.   

Edited by Ko.Fe.
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