I normally use the KISS technique with the kit lens; Aperture priority, Auto focus, Auto ISO, maximum exposure of 1/2f and multi-field metering. Most of the time this works well enough.
I have to photograph house interiors – I'm house hunting – and like to take a few images to send to family members elsewhere in Europe. I find that estate agents (realtors) can be rather selective in their photos in the brochures or on-line; they mostly use 28mm equivalent lenses. I'm not looking for perfectly exposed, focussed and composed images – there isn't the time for this, rather ones that show the rooms 'warts and all' – and many rooms in the UK and Ireland are really quite small. I'm not concerned about the contrast between inside and outside, I just want to see what the interiors are really like.
But...using the WATE at 16mm with this set-up doesn't work. As I stop down, not only does the EVF get darker, but the histogram bunches up to the left. I have very generous ISO limits (up to 25,000), noise in these circumstances doesn't worry me. I tried various combinations of maximum shutter speed, but this had little effect. The ISO might rise a bit, but the image was still underexposed.
I tried centre-weighted metering; the same thing happened, the ISO would rise a bit, but the image was also bunched to the left and underexposed.
I then tried spot metering, and this works as expected; as I stop down, the ISO rises in parallel, and the images aren't underexposed.
What's going on? What am I not understanding now?