Why is the subject too dark when using auto modes on Nikon D5600?

Question

I have a problem with using automatic and semi-automatic modes. For example, I have "fairly optimal" light, in "A" mode I set the desired aperture value, let it be 2.8 and ISO 200, when I switch to live view mode on the LCD screen, everything is ok, depending on the conditions I get low shutter speed (down to 1/800s). After switching to the viewfinder, the time increases immediately to huge values, even up to 30 seconds. I can change ISO and aperture both ways, but the time does not change either at all or the change is minimal, it "works" the same in any automatic mode, I tried it for both lenses, for different lighting conditions. The LCD screen displays a warning that "the subject is too dark", the time does not change when I put my eye to the viewfinder. Pictures come out all white (no surprise), in addition, in the AUTO mode the flash always fires.

I restored the factory settings, reset all user settings, formatted the memory card, downloaded the current firmware from the Nikon official website, and reinstalled. Nothing has changed:

• LCD preview: ISO 2000 and 2.8 aperture, the shutter speed has been set to 1 / 500s, the photo is ok.

• View through the viewfinder: ISO 2000 and aperture 2.8, the shutter speed changed to 30s, while i changed the exposure compensation to -5.0, the time dropped to 1 / 20s, the photo came overexposed.

In manual mode (and automatic when previewing on LCD) everything works rather well, I took several hundred photos and I did not notice any problems with sharpness, the changes in parameters are visible, I'm even able to shoot in weak light conditions, so I do not understand if my Nikon is simply faulty, whether I am doing something wrong or do not understand something about its principle of operation.

Answer 1

While there are many differences when shooting in Live-View compared to the Viewfinder, the one that seems the most applicable to these observations is that a dedicated metering sensor is used while shooting using the OVF.

The warning that constantly appears is consistent with the long shutter-speed chosen and, given that Manual exposures work, it is highly likely that the metering sensor is to blame.

It is possible the metering sensor is dead but hopefully not. It might be obstructed or dirty. One culprit could be the mirror given that it needs to let light pass to the sensor. Try to clean the mirror and check if things improve. If not, then you may have dirt below the mirror where the sensor is sometimes located. Many DSLRs have it in the viewfinder chamber but I don't know where it is on this particular camera. This is why we often see the warning on a focus screen saying "improper installation may interfere with metering" or something similar. Clean gently anything you see dirty or else bring it to be serviced professionally.

Answer 2

As Itai suggests, it's probably the light metering sensor in the viewfinder.

So, you are able to see a reading at high ISO, wide aperture and negative compensation, do the numbers/meter blink then? Many/all Nikons do that when it's getting too dark to meter.

Does the meter react to bright daylight at all, when you set it like that? I think it might not, because in a dark room, lens cap on, our D610 at ISO 2000, 2.8, -5EV meters 1/25 s matrix, 1/40 s spot or 1/20 s center weighted. (Lens 50mm/1.8 AF-D)

If it seems dead in daylight, it probably isn't dirty or obstructed, it's just broken. It's probably going to cost a lot to fix, and you have to think about just learning to expose manually without the meter, it's not that difficult with a digital camera.

What really confuses me is that +5 EV from 1/20 s is about a second, not 30 seconds. Did you change the ISO or something else there also?

Answer 3

Your light meter, or its connection to the camera's "brain", is broken.

When in Live View the camera uses the main imaging sensor to do metering.

When using the viewfinder, the mirror prevents the main sensor from receiving the light projected by the lens. So there is a dedicated light meter, usually placed in the prism/viewfinder area, that measures the amount of light gathered by the lens and projected by the mirror onto the focusing screen, which is what you see in the viewfinder.

Your description of the issue sounds like the camera is using the default minimum value for the light meter reading. This seems to me to be saying either the meter itself is broken, or the connection to the camera's processing chip has failed. It may be something as simple as a ribbon cable between the meter and the camera's main board working loose, or it may be a more serious issue with the circuitry on the main printed circuit board.

You can test this by putting a lens cap on and seeing if the meter readings change at all from when the uncapped lens is pointing at a bright light.

I'd caution you about trying to clean around inside the camera's light box. Both the mirror's surface and the focusing screen surface are two of the most fragile and easily damaged components of any DSLR. I have no qualms whatsoever about cleaning the sensors in my digital cameras using swabs, but I do not use any contact method to clean either the mirror or the focusing screen. If an air blower doesn't remove it from the mirror or focusing screen, it stays. A dirty mirror and/or focusing screen do not affect image quality at all, since the light recorded by the camera's sensor does not bounce off the mirror or go through the focusing screen on it's way to the sensor.

The problem you are describing is much too severe to be caused by dust or smudges on the mirrors, focusing screens, or sensors inside the camera's light box unless they're almost coal black.