M8: How does it know what F stop Im using?

[dude163]

The camera is magic!!


how does it detect what f stop I am using, even though the lenses are manual?

Is it some light detection algorithm? or a mechanical connection between the lens and camera?

Thanks

 

[jonoslack]

The camera is magic!!


how does it detect what f stop I am using, even though the lenses are manual?

Is it some light detection algorithm? or a mechanical connection between the lens and camera?

Thanks

It makes an educated guess . . . good though!

 

[dude163]

I agree

look atthis

http://www.flickr.com/photos/riverviewfoto/5561784732/meta/

its 100% correct! and when i was using f2.8 and f2 it was correct then also

LEICA!!!

 

[dfarkas]

If you look at the front of the camera, there is a small bluish dot to the upper left of the Leica red dot. This is a secondary light meter. It takes an EV reading then compares the current shot's ISO and shutter speed to calculate the aperture. While not 100% accurate due to the reading not being through the lens (TTL), it is usually within a stop of the actual aperture.

David

 

[Per Ofverbeck]

....how does it detect what f stop I am using, even though the lenses are manual?...

One might say the M8 (and the M9) has two exposure meters. One measures light through the lens, and that´s the one that actually determines exposure times in Auto, or generates the readouts in Manual.

The other, simplified one has its cell in the little round window just beside the Leica ´red dot´. It measures light falling directly on the front, and so has no idea of the f/stop set on the lens, but the coding on the lens (or the manual lens setting) tells it the maximum aperture (it also probably helps in setting auto white balance, but that´s another thing).

So, the difference in reading is assumed to depend on how much the lens is really stopped down, and thus the f/stop setting can be computed.

But, just as an old-fashioned MR meter with external cell is usually less accurate than a TTL meter (influenced by stray light outside the image field & c), this comparison doesn´t give exact results.

Edit: Dave beat me to it, just when I was writing....

 

[HenryFool]

That's pretty cool, it's not working for me though...

http://www.flickr.com/photos/henryfool/5531809378/meta/

I'm guessing that the lens has to be coded for this to work???

 

[dude163]

I dont think it has to be coded as my cron is from 1964

 

[dfarkas]

I'm guessing that the lens has to be coded for this to work???

For focal length and max aperture data, yes, you need to be using a 6-bit coded lens on the M8. The M9 has an option to manually select the lens from a menu.

LR and C1 display aperture info. I don't think Aperture reads and displays this info (a little ironic, actually). Any Aperture users want to chime in here?

David

 

[HenryFool]

I don't think Aperture reads and displays this info (a little ironic, actually)

LOL

 

[dannh]

Unfortunately, this system doesn't work very well when using a strong ND filter. I guess that makes sense though, there's no way for the camera to know what you're putting in front of the lens, and obviously a lot less light is getting through.

 

[peterc]

LR and C1 display aperture info. I don't think Aperture reads and displays this info (a little ironic, actually). Any Aperture users want to chime in here?

David

its true, Aperture can't display the aperture...
I was pleasantly surprised when I used C1 and got the aperture info

Peter