Exposure metering limit confusion?

[lejazzcat]

Hey all,
HAving lots of fun with the new toy , but
I wonder if anyone else has encountered this conflicting reading readout when doing long , night exposures, in S or A modes.
(no flash and no compensation)

I set say a 10 sec exposure(S mode), or the aperture at f1.8( A mode).

I take a reading of a dark scene , but get a "LO" in the viewfinder at either the user set shutterspeed, or aperture, but, then when I recompose the subject so that it includes the light source in the composition, it tells me i have heaps of room to play (either with shutterspeed or aperture). Im aware that it seeing the light ....

I recompose to eliminate the light source and the "LO" reappears in the viewfinder,I fire the shutter and the camera exposes the scene ...well enough.

But heres the problem- i take a look at the exif info of the exposure, and it tells me it had plenty of room to play with exposure !
Lets say im in S mode (5sec) - ill get a EXIF exposure at F4.5 made with a f:1.8 lens !
Why did it say it was too "LO'' to get a correct exposure if it made its "correct" exposure at f4.5 ?> why didnt it need to go to wide open if it was "LO" ?

theres nothing in the manual that i saw that explains this discrepency . Any ideas?

Confused...

[theK]

What metering mode are you using?

The metering mode chosen affects the suggested aperture/shutter speed in the shooting modes other than M.

Spot: Only measures a small roundish area, depending on the focus point chosen.

Center-weighted: Measures a larger roundish area, just slightly smaller than the circle visible in the VF. Best for portrait.

Matrix: Takes measurement from 1005 cells spread evenly on the frame. This metering mode takes the average of the exposure settings required.

I don't use P or S shooting mode, so I can't comment why it chose f/4.5 instead of f/1.8 when the light was low. I usually use M or A, since I dial in my settings starting with the DOF that I will need for the shot.

[lejazzcat]

I tried both Matrix and spot.
I think that spot is less sensetive , but thought ide try it to test the exposure...

I know what your saying - i also tend to use the A mode, but because i can see the effect the shutter speed has on my aperture i can balance one against the other.
The problem is the same - if i set it to A - ill get a "LO" where the shutter speed time readout should appear, and visa versa if its set to S.

Even if i set the shutter time to 30 sec - it still says "LO"
but the actual exposure would be something like 5 sec when i look at the EXIF afterwards...

Its really painful, as i would prefer to be able to set it to A and get a exposure reading that tells me what the length of the exposure will be in advance, so i can anticipate the effect ....

[pippin88]

I didn't understand what you meant at first but now I do.

I've noticed this too, where it will say LO and then expose a scene correctly with much less time. I always expect it to go for the max shutter time possible.

I have no idea why or how it does this, or if the LO reading in these cases is a bit off?

[lejazzcat]

well thank god someone else has seen this problem - i thought my d70 was stuffed.
Sorry i probably didnt explain it as well as i should - i guess i understood the explaination - but even i was a bit confused .

Thanks Pippin!