meter reading question


TPF Noob!
Nov 5, 2008
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Warwickshire UK
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ok, ive been struggling to understand metering since day one. i am using an example and hopefully some one can explain. I took a shot in manual mode on my D40. Nothing exciting, just a black bag sitting on the sofa. No flash etc, under artificial light. According to the meter if i wanted a 'correct' ex[osure, with the meter bar in the viewer reading in the middle at 5.6 i would need a shutter speed of 5 seconds, which results in an overexposed image. However if i move the shutter to about 1/6th the viewer shows that the image will be very underexposed, with the meter way off to the right hand side, however this 1/6th @ f/5.6 gives me the best exposure. Im on spot meter mode.
and which spot did you meter?
with the central focus point at a black area if the bag, some other areas of the scene were not black, including a zip and the sofa but generally the shot looks well exposed, or should i say it looks like the bag
basically anything i point at seems to only get a true exposure if the meter is adjusted so that it should in theory be underexposed
Post the example shots. Probably the best way for people to understand and to help.

A few questions that I can think of....

It is a black bag, what is the rest of the scene in comparison, bright colors, dark colors, brightly lit, darkly lit? Is there a lamp or lightsource within the scene itself? What do you mean by over/under exposed, the entire scene or just the bag as a subject? These are the questions that can be answered with example images.

Oh, and some cameras just simply underexpose or overexpose. I think others have mentioned that they use exposure compensation set all the time to get correct exposure on the D40 (which direction I can't remember.) My own camera, I always either set -0.75 to -1.0 exposure compensation or I set in manual to show -1.0 exposure compensation at all times.
ok this is the overexposed image, obviously a blurry one as its no ton a tripod and is just for test purposes. This image stated the exposure was correct in terms of the meter bar reading, somewhere in the middle f5.6 at abt 4 secs shutter, overexposed as you can see

and this is the image with a shutter of abt 1/5 or thereabouts showing totally underexposed on the meter bar but obviously this image is the better of the two and is exposed ok
In those two pics, where did you point the spot meter to take the reading ?
Also, I think on the D40, like my D90, each tic-mark on the exposure line is equal to .5 stop. So how many tics was the bottom shot reading underexposed, and compare that to how many stops difference between the two shutter speeds.
It should pretty much equal out so that if you increase shutter speed by 2 stops, your meter should read underexposed by 2 stops ( 4 tics ? ), all other things being equal, including that you meter on the exact same spot both times.
when u say where did i take the rreading from do u mean where did i point the camera?? at the subject as u see it which is black in the centre of the image. with the 2nd shot the bar was right over to the right hand side, the 'correct ' exposeure was with the bar in the middle and resulted in an overexposure so either the d40 is crap with metering or i am doing something wrong. why would the correct exposure show an underexposure on the meter? surely correct shd be in the centre or whats the point in the meter if u assume middle is correct and find out it isnt?
Ok so you're saying that the second picture is an accurate representation of what the bag looks like, but the meter was reading a certain number of bars underexposed ?
How many bars ? Was it at least close or was it pegged out to the left ?
I didn't think that the bag would be covering nearly the entire frame....

Someone else can pipe in better here soon because I need to go do some work, but...

Take a look at the various threads on shooting snow that has come up quite frequently in recent past since we are just about done with winter soon. It is the same concept except the exact opposite. Basically, nearly the entire frame is black and the camera is trying to expose to 18% grey. When this happens, it will end up overexposing on the meter just as it has with yours.

The opposite is snow. The camera again tries to expose to 18% grey and will underexpose the meter because of all the white.

Give a quick search on "shooting snow" and have a read of those threads. Think about what the exact opposite would be and you would have your problem.

That's my take on it. Someone else can come in with a better explaination, or correction of my explaination even. I have to go do some work before quitting time.
Yea I was assuming that what Puyjapin posted was the whole picture. If that's just a little part of the picture, then it's still possible he was metering on something else.
PJ, have you tried to get your camera in meter mode ( half press the shutter ), and then move it around a bit while your eye is in the viewfinder and watch the meter move as the lens moves ?
When you spot metered the bag ... the meter will provide you with the exposure to render the bag as 18% grey ... which will over expose the bag since it is black.

In this situation you should know to under expose the shot to render the bag as black. So your meter was correct ... it was you understanding of what the light meter is doing that is throwing you off.

Same thing would go with a very white object (but in reverse).

If you really wanted to render the bag correctly ... put an 18% grey card in front of the bag and meter off it ... then take the shot.

[ OK, I have just repeated what MRogers stated ... hmm teaches me for not reading the thread closer before posting a reply ]
if this is a black bag then I'm a carrot, looking at this page I see red, black, white, gray,blue, the bag is brown. H

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