D850 Exposure setpoint shift

Well, yesterday my D850 started under-exposing consistently about 1 stop. I tried multiple lenses, autofocus and manual. In general, I stay in aperture priority, and use matrix metering. We all know that matrix metering is slippery, with the focus point location altering the exposure for the same framing. Exposure compensation is at zero and b7 (fine tune optimal exposure) is zeroed out. It is a clear change in the meter set point. I don't know any other settings that might do this. I tried a reset of the camera (forgot that that would delete everything from "My Menu"). It may be time for a trip back to Nikon.

Any suggestions?

Have you tried cleaning the lens contacts on the camera body?

You also might want to look at the AI follower on the camera to make sure it's not got distorted or has any crud stuck to it.

Does it happen at all apertures? Even wide-open?

Check the aperture actuator in the camera hasn't got stuck or bent. That happened on an old F4 once.

Well, yesterday my D850 started under-exposing consistently about 1 stop. I tried multiple lenses, autofocus and manual. In general, I stay in aperture priority, and use matrix metering. We all know that matrix metering is slippery, with the focus point location altering the exposure for the same framing. Exposure compensation is at zero and b7 (fine tune optimal exposure) is zeroed out. It is a clear change in the meter set point. I don't know any other settings that might do this. I tried a reset of the camera (forgot that that would delete everything from "My Menu"). It may be time for a trip back to Nikon.

Any suggestions?

Does it underexpose if you change the metering to Center weight? Spot? Or does it underexpose in all metering modes?

Well, yesterday my D850 started under-exposing consistently about 1 stop. I tried multiple lenses, autofocus and manual. In general, I stay in aperture priority, and use matrix metering. We all know that matrix metering is slippery, with the focus point location altering the exposure for the same framing. Exposure compensation is at zero and b7 (fine tune optimal exposure) is zeroed out. It is a clear change in the meter set point. I don't know any other settings that might do this. I tried a reset of the camera (forgot that that would delete everything from "My Menu"). It may be time for a trip back to Nikon.

Any suggestions?

I would test the meter accuracy and the ISO

Before sending the camera away, I'd try to re-install the firmware - if possible.

I don't know if there's been an update published yet, and even if there has, the camera may not let you install the same version twice. Worth a go though.

There was a firmware update about 10 days ago, that I installed. I haven't had time to do any careful testing so am not sure if things are settled down or not. Funny how once you decide the exposure is "off" it is difficult to tell if the exposure is correct, especially in high contrast scenes.

You can reinstall the same firmware by the way. Did that. Maybe tomorrow I can get time to test my camera.

Thanks again.

The only way to test it really is by comparing it to another camera or a handheld meter.

You can also do an approximate self test to see if it's giving a believable exposure. All that's needed is an A3 sheet of card or copier paper and a source of steady and even light.

Stop the lens well down to f/8 or f/11 so that vignetting isn't an issue. Set the camera to manual focus, base ISO and auto WB. If the camera's on a tripod, make sure the eyepiece is blinded. Light entering the eyepiece will almost certainly affect the reading. Obviously you need to zero any compensation or exposure fine-tuning before you start.

Take an exposure at the camera's metering, or let A mode do its thing. The resulting histogram should show a fairly narrow spike just to the right of the centre line - about 1/3rd towards the first division line.

Now set +2.3 stops exposure compensation and take another shot. This should take the histogram spike to just short of maximum. Setting +2.7 stops compensation should send the spike hard over against the RH side of the histogram. This will also show as a large shaded area in the 'blinkies' screen.

Much the same should happen in each metering mode, although there might be a small variation between modes.

If this doesn't happen, then there would seem to be a fault or mis-calibration with the camera's meter.

I believe the D850 has a 'highlight preservation' metering option. Make sure this is turned off.

I just remembered.

Active D-Lighting also monkeys around with the exposure. Make sure that's turned off too.

Thanks rodeo joe. So following your instructions, my meter is darker by 0.7 stops. This is true in matrix metering or in center weighted mode. With no exposure comp I am to the left of the center of the histogram. a 0.7 increase puts me to the right. A 2.3 top exposure comp is not near maximum. A 3.0 compensation does that (0.7 plus 2.3). I have to go 3.7 to get hard against the right side.

I can short term do an exposure adjustment of 0.7, but the fact that it changed suddenly 5 days ago is concerning.

Thanks rodeo joe. So following your instructions, my meter is darker by 0.7 stops. This is true in matrix metering or in center weighted mode. With no exposure comp I am to the left of the center of the histogram. a 0.7 increase puts me to the right. A 2.3 top exposure comp is not near maximum. A 3.0 compensation does that (0.7 plus 2.3). I have to go 3.7 to get hard against the right side.

I can short term do an exposure adjustment of 0.7, but the fact that it changed suddenly 5 days ago is concerning.

-That definitely sounds abnormal to me. Especially since my past experience with Nikon's metering is that it has a tendency to overexpose.

Time for a trip back to Nikon I think! :(

Sorry to be slow on followup. I sent the camera back to Nikon repair in New York. It came back in a week, with a note of adjusting the exposure and white balance to factory standard. It is working fine. They gave no detail on what if anything was wrong or why.

As an aside, the last lens I picked up before the problem developed was a Nikon 50-135 f3.5 manual focus. It still seems to have a malfunctioning aperture lever, so I am left wondering....