It was reported here that using the emf chip if using the 2nd mode while reporting the max aperture to the cam, the metering system will read correctly with no non-linear
errors at different apertures. Seems the max aperture may affect how the metering cells
see the light intensity in the VF housing? Does this really eliminate all metering errors at all apertures with alts?
Mike
I don't know about the max aperture reporting, but when using center weighted metering, I don't have metering errors stopped down on 5D. I should give a try at matrix metering again through the aperture range and see what happens to test the theory.
The EMF chip works like this:
1. meter with the aperture on the lens set to wide open
2. lock exposure (AE lock)
3. set aperture on the camera -- this is unique to the EMF chip and calculates the exposure based on the locked exposure value
4. set aperture on lens to desired value (if other than wide open)
5. release shutter
I got a Contax adapter with EMF chip from big_is but found that my lenses don't reach infinity focus with it. On top of that, the focus confirm seemed to be WAY off with the default setting and the metering didn't seem to be more accurate, or at least too unpractical to use as described above.
Maybe I'll do an exposure series with it to test the metering...
A friend reported that the aperture priority mode provided fairly accurate exposure when the correct wide open aperture is reported. I can't test a only have Optix V chips now. I was a bit surprised
My 5D's metering always gives deviations when stopping down. I have an Opix V5 and some generic chips and also without chip and the deviation is the same with all. I got used to dial in some EC to compensate for the underexposure when stopping down.
I can't say why, but I my system seems to be slightly different and works for me every time:
1. set the aperture on the lens to wide open
2. set aperture on the camera
3. press the shutter button lightly to take a meter reading then set AE lock
4. set aperture on lens to the aperture set on the camera
5. take picture
Maybe it doesn't matter if AE lock is set before or after setting the aperture on the camera and metering – I have not tried that.
rtallent wrote:
Maybe it doesn't matter if AE lock is set before or after setting the aperture on the camera and metering – I have not tried that.
I think it doesn't matter in which order you do it. The locked exposure is based on what is metered, not the calculated exposure. The only thing that matters is that you do the metering with the lens wide open.
This is confusing. So I take it the Optix V chip and emf report the aperture the same way to the cam and that alone will NOT fix the metering error while stopped down?
So there is something about how the light hits the metering cells off the screen while stopped down that fouls up the metering that is somehow different than just putting ND
filter in front?
As far as I know, the EMF chip is the only one that allows changing the aperture on the camera, to allow wide open metering and calculate the stopped down exposure (as the system is designed).
The problem is, like you say, with stopped down metering. I believe stop down metering is just as inaccurate with the EMF chip as with other chips, because it's the brightness of the focusing screen that doesn't correlate perfectly to the actual amount of light let through the aperture.
