testing lightmeter accuracy against digicam?

[atelier7]

Hi,

I'm trying to test out the accuracy of my sekonic auto-lumi model 86 light meter by comparing the readings against my canon a610 digicam.

Need to know if i'm doing this correctly.

I take readings from my sekonic meter by pointing it at my open palm, about 6 inches away. I then do the same with the digicam set on aperture priority mode.

I have both set at ISO400 and f8, and read off the shutter speed.

Would this be a fair test of the accuracy?

Indoor reading under flourescent tube- 1/30 canon vs 1/20 sekonic

Outdoor reading (grey skies) - 1/160 canon vs 1/250 sekonic

 

[kaiyen]

You are merely comparing the metering of the two cameras in relation to each other. One is or is not accurate to the other. That doesn't mean that both can't be wrong.

You also have to consider stuff like metering pattern and also keep in mind that meters in many digital cameras make assumptions based on sensor response characteristics that aren't necessary with handheld meters.

allan

 

[kully]

I have the same thing with my Canon G5. I found out a few months ago that the Canon ISO equivalence is on the conservative side and that ISO 50 is actually ISO 64, ISO 400 is ISO 640 &c. &c.

Seems like your meter is working grand (if you A610 has the same 'feature' as my G5).

 

[atelier7]

thanks for your input.

 

[Finder]

Hi,

I'm trying to test out the accuracy of my sekonic auto-lumi model 86 light meter by comparing the readings against my canon a610 digicam.

Need to know if i'm doing this correctly.

I take readings from my sekonic meter by pointing it at my open palm, about 6 inches away. I then do the same with the digicam set on aperture priority mode.

I have both set at ISO400 and f8, and read off the shutter speed.

Would this be a fair test of the accuracy?

Indoor reading under flourescent tube- 1/30 canon vs 1/20 sekonic

Outdoor reading (grey skies) - 1/160 canon vs 1/250 sekonic

I can see problems. First, have you determined your camera meter is "right." Second, there are a number of variables that can affect readings. The distance to metered area, the measuring angle (both the meter and camera must be measuring from the same position and have the same metering angle), the t-number of the camera lens, the spectral response of the metering systems and CCD. Why are you using your palm instead of a gray card? Did you test the exposures with the camera to see which was better? I would say this "test" does not give much insight to the accuracy of either the camera or meter.