How does metering works on a D40 in manual mode

[Resel]

I need some help here...I have a Nikon D40 and try to figure out how to work the metering when in manual mode. I'm trying to set the meter to a 18% gray scale, or at least something close to it, before taking a picture in order to get a more "true" coloring in the photograph. I got the advise from critices that in some of my pictures I need to "meter of" a different piont in the picture before taking the picture.
Well I guess I'm a little confused with the whole thing. Can somebody explain it to me?

Thanks a lot.
Astrid

[inkista]

You don't have to be in manual mode to bias the metering. Just so's you know.

Metering is nothing more than measuring the amount of light coming in. You camera has multiple metering modes so that you can tell the camera which bit of the scene you want to be measured. By default, the camera is probably set to look at the entire scene and do some form of averaging. It takes that average value, sets it to the "middle gray" value and then sets exposure accordingly (if you're in an automatic metering mode).

But you can also tell the camera to place more weight on the values coming from the center of the frame (center-weighted), or one particular area of the frame (spot). It will do the same thing of averaging the values, but with center weighted, it gives more importance to the center of the frame values, and with spot, it ignores most of the other values.

The problem with this kind of metering approach, though, is that the camera is dumb and just does this mechanically. It's just looking for an average/median value to set to middle gray. If your scene is predominantly black or predominantly white, a very dark or very light value will be set to middle gray, and a black scene will be overexposed, and a white scene underexposed as a result. So, sometimes you want to bias the metering.

In the automatic modes, like aperture-priority, you can do this with "exposure compensation". You can dial in that you want the scene a little darker or a little lighter.

In manual mode, you dial in the needle to be to the left of 0 in the - direction if you want it to be darker, and to the right of zero in the + direction if you want it lighter.

Metering off the sky/grass/whathaveyou, would mean filling the frame with the sky/grass/whathaveyou, and then locking in the exposure settings for that, before reframing and taking your picture. In Manual mode, that would mean setting the meter "needle" to zero when the sky fills the frame, and then not adjusting your settings afterward when you take the shot. In Aperture or Shutter priority modes, it would mean pointing at the sky, pushing the AE lock, and then reframing to take the photo. Or, you could use spot metering and make sure your spot is placed on the sky/grass/whatever, but that's a bit more hit-and-miss in practice I've found.

[Shokinen]

Nice reply Inkista.

[zona5101]

tagging on to Inkista's excellent post...
So there are two things I am hearing: metering for exposure and color balance.
Metering for exposure – the meter inside your camera thinks everything is 18% reflective gray. When a subject is brighter or more reflective that this the camera will underexpose the picture. Think of a photo of snow, camera will try and make all that nice white snow look gray. Because of this we use +/- exposure control, spot metering or manual settings on our cameras so we take control and not let the camera make the snow gray.
In your case, some folks are saying you should meter a different part of the photograph, would say to me your camera tried to make something midtone (gray) that should have been a highlight (or a shadow).

On to Color Balance: This has to do with the bias in color from different light sources and your camera’s white balance setting. In sunlight, with your camera set to daylight no issues, or like my friends to the north like to say “Bob’s your uncle”. When there is a mismatch between the camera white balance and the light, we get color shifts that make things the ‘wrong’ color – like back in the day when we used daylight film indoors and everybody looked kinda orange. So how to fix that is to change the white balance setting on your D40 to match the light you’re in. Sometimes the choices in the camera aren’t precise enough, we can create a custom white balance setting. Your manual will tell you the specific steps but you would use a white card or a gray card to give the camera a reference point for determining the proper color correction.
Besides creating a custom white balance setting inside your camera, you can use a gray card as a reference point for your post processing application. First take a shot of your gray card then take your pictures. When you post process you color correct all the pictures from that session with the correction applied to that first gray card image.
I hope this helps. Good luck and have fun!

[RLucas]

Inkista is spot on with that. But, if you dial to the left of 0 it takes it lighter, and to the right takes it darker. The D40's matrix meter has really never been up to par with some of Nikon's other cameras. It tends to overexpose if you are using any of the auto settings. You can set your exposure compensation to -.7 to-1ev, and it will take care of a lot of the problem.

In manual mode, I tend to keep it set to spot, and expose for midtones. If I am outside, I use grass, or the road, or something of that nature. It usually does the trick. You may still have to adjust it to your particular tastes either way.

[inkista]

Originally Posted by RLucas

Inkista is spot on with that. But, if you dial to the left of 0 it takes it lighter, and to the right takes it darker. ...

Holy cow. I never noticed Nikon's exposure scale goes the other direction. Canon's follows the histogram of left = dark, right = light. I gotta stop using "expose to the right" as an expression.

[Shokinen]

Originally Posted by inkista

I never noticed Nikon's exposure scale goes the other direction.

Not sure with the D40 but I know you can reverse it with the D90. The option is available in the menu.

[LoveDSLR]

You are turning your D40 meter into an incident meter when you meter a 18% gray card/object.

If light falls onto the subject the same as the gray card/object then the exposure reading is optimal and you don't have to do selective metering and EV compensation (that is for reflective mode metering or personal preference).

If you are using semi-auto mode (Aperture preferred or Shutter speed preferred) then you can do a AE lock after metering the 18% gray card/object (D40 manual, page 77: press the AE-L/AF-L if you set it to 'AE lock only').

For manual metering, refer to page 43 of the D40 manual.

- Rotate the command dial to M.

- Select an ISO value (e.g., 200) and choose an aperture. Rotate the command dial to set the shutter speed until you see Optimal exposure ('0') from the Electronic Analog Exposure Display.

You may have to increase the ISO and/or adjust the aperture to achieve optimal exposure.

[RLucas]

Originally Posted by inkista

Holy cow. I never noticed Nikon's exposure scale goes the other direction. Canon's follows the histogram of left = dark, right = light. I gotta stop using "expose to the right" as an expression.

The Canon scale would actually make more sense to me. Just put a disclaimer "expose to the right of the histogram'? ETTRH?

I don't think the D40 has the reverse option. If it does, I am going to change it right away!

[OsmosisStudios]

Originally Posted by inkista

Holy cow. I never noticed Nikon's exposure scale goes the other direction. Canon's follows the histogram of left = dark, right = light. I gotta stop using "expose to the right" as an expression.

For some reason I though Pentax did the same thing. It makes more sense in my head: if im turning the shutterspeed dial to the right, the indicator in the meter goes to the right (Darker) and the shutterspeed number goes up.