Modifying metering pattern on M6 possible?

[sergio_ortega6]

I was explaining the purpose of the little white dot situated on the

inside of the M6's cocked shutter curtain to a friend. From what I

understand about the M6, the light passing through the lens and onto

this white dot is reflected and measured by the meter.

 

My friend asked a rather simple theoretical question, one for which I

had no answer: If one were to reduce the size of this white dot,

would the central area metering pattern be changed?...perhaps to a

spot metering pattern?

[joshroot]

I think it would also involve narrowing the field of view of the metering cell also. Otherwise the meter would just be measuring the light reflected from a smaller white circle surrounded by a black circle.

[roberto_watson_garc_a]

Interesting Sergio, we can think in a larger circle, could be very helpful in an autoexposure M7 too. Just have to see of the reading angle of meter inside, like other rangefinders.

[jay_.]

Josh is partially correct. It would not be necessary (nor practical) to alter the cell's angle of view; however some testing would be required to establish a set degree of compensation (changing the ISO)to re-calibrate the meter's accuracy. The reduced reflective area might also limit the lower threshold of sensitivity. I've heard of this being done; however in practice the M's metering has always been selective enough for me. (In situations where a true spotmeter is essential the M is rarely the camera at hand--except landscapes while backpacking, where I use an M4 and a handheld Sekonic L-408 anyway.)

[al_kaplan1]

It would modify the coverage, but it would still read some light off the surrounding black curtain which could affect the reading, for instance a very bright light just outside the white dot. The meter would also have to be recalibrated, because it would ALWAYS be getting less light to the cell.

[michael_bender]

The meter is calibrated to receive a certain amount of reflected light to, say, report that 8/125 is the correct exposure. Modification of the spot position and/or size and/or shape will - under the same lighting conditions - reflect a different amount of light to the meter.

 

The best thing to do is test your camera and know where the outline of the spot is, precisely, in the viewfinder.

 

How to test?

In a darker room use a flashlight to throw a small bright spot on a wall. Set the camera to expose correctly or slightly overexpose on the spot. Move the camera and notice when the indicators will say "-" That will outline the metering spot on its -2EV (or -1.5EV) level.

[doug_hagerman]

It sure seems to me that you could use flat black paint (problem: finding flexible flat black paint) to reduce the size and/or change the shape of the white dot. Sure, you'd have to change the ISO setting, but so what? Cut the area in half and your film's speed just went up by 2x.

[john_collier2]

http://www.jumboprawn.net/jesse/metering_spot.html

[sergio_ortega6]

It's really amazing the stuff you can learn on this Leica site. I should have known someone out there would already have thought of this, modified their M6 and then posted the results on a website. Thanks everyone.