Help calibrating L358 to D800
Was on a shoot last night with my new D800 and noticed that every time I metered the ambient with my Sekonic L358, it was about 2 stops off. If the meter said 1/500th @ f2.8, I'd have to shoot around 1/1200-1/1600th to get proper exposure. Proper exposure was tested by breaking out my PhotoVision Digital Target ( http://www.photovisionvideo.com/digital-targets/ ) and checking the histogram for proper exposure. This morning I tweaked the L358 to +1 exposure and the shots are coming up almost exactly 1 stop under-exposed. If I double up my ISO (going from 100 to 200) or halve my shutter speed (dropping from 1/200th to 1/100th) my Digital Target/Histogram shows dead on exposure. Making sure this wasn't a problem with the D800, I got out my D7000 to see what settings it would give me in the exact same conditions. Again, with my L358 at +1, it was 1 stop under-exposed. Doubling the ISO or Halving the shutter speed gave me perfect exposure. My question is, the L358 will only allow me to go to +1 compensation. Can I send this in to have it recalibrated? Do I just accept this and know that I have to always add +1 exposure in the camera from what the L358 says? Thoughts?
2 stops off is far from just a calibration error. As there might be more involved I'd send it in to avoid increasing future malfunctions.
I know that you are pointing the lens to the calibration target to get the exposure for the camera. Are you by chance pointing the sensor of the meter, with the diffuser disk on it toward the target also?
If the answer is yes, then you should either leave the diffuser disk on and point it toward the light source, or take off the diffuser dish and point it toward the target. This would account for that two f/stop difference you are encountering.
Place your meter flat against the chart with the dome extended and aimed at the camera when you take your reading. This is the way Sekonic recommends you use the meter and it WORKS!
Now if the meter reading is off more than 1 stop then something is wrong. First go to Calibration Compensation on page 26 of the manual. Check to see if you have any Calibration Compensation already being applied. If you don't then you should send the meter in for recalibration.
You can enter a Calibration Compensation value of up to ±1 stop but if my L-358 was off by more than about 0.5 stop I would send it in for recalibration. Mine has never been off by more than 0.2 stops.
Check with each lens and camera. There are tolerances with aperture openings and sensors so f/8 with one lens & camera may be f/7.9 or f/8.1 with another camera or lens. A strip of tape on the meter with the offset for each lens or camera written on it is a good way to remember.