Thanks useful information: 
LOL!Originally Posted by Steve Axford
I almost confused myself at one point. After posting it I tried to read it back but was rushed not to burn dinner, get the kids fed and then off to their taewkondo.
I actually don't think understanding the technicalities of it all is important.
That is, who really cares if a large room lit with a single 100W globe represents an Exposure Value of about 5 or 6 .. or that the Moon has an Ev of 15 .. but that a (full)moonlit night is 4 or 5?
The problem being that every camera sensor is probably different(slightly different sensitivities), I can't think of any camera that doesn't have an exposure meter .. so this is probably the best guide to Ev requirement anyhow(except for specific purposes when you're adding your own special lighting into the scene).
These exposure tables were created for film(obviously in the film era).
While some films are different to others, you still have the situation where two different cameras can have film of a similar brand/type .. and this would be where the Ev tables could help with consistent exposures between different gear.
But in general, my three cameras all produce slightly different exposure results using the exact same lens, and exposure values in camera.
If I remember correctly ... I think the D70s is darkest, D300 comes in at mid range, and I've noticed that the D800 comes in brighter for their resultant images.
It might not be all that much different, maybe 1/6-1/3 Ev difference, but it is different.
I expect different exposures from the D800 over it's entire frame as it's a different format, but even in Dx crop mode it shows a brighter exposure over the D300(maybe by only 1/6 Ev tho).
Also, for the OP .. the way to visualise how exp-comp is recalibrating your cameras meter, and nor directly referencing the Ev of the scene .. set your camera to manual mode.
In Manual mode, you don't actually have access to exp-comp per se .. (you do but it works differently to how it does in the Semi Manual modes)
That is, the definition of manual mode is that you have to do all the hard work yourself.
BUT! You can still use exp-comp(or at least you should), and the way it works is different to how it does if you're in Aperture priority or Shutter priority modes.
In the latter two modes you will see a visual indicator in the meter indicator(which could be what's causing the confusion). So it's showing you that it's going to be different to how it thinks it should be.
In Manual mode, with exp-comp set, you don't see this same indication in the vf. You may see that the meter shows a certain expected brightness or exposure, but you adjust the cameras exposure parameters to achieve a neutral point if you want too.
If you set exposure compensation whilst in Manual mode, you still see the same meter indication but the exposure parameters will be different.
An example of this could be something like you've set 1/10s, f/2.8 and ISO 100 on a plain evenly lit surface, and the meter reads 0Ev on the bar indicator.
If you set -1Ev(still in Manual mode) to get the meter to read 0Ev, you now have to change one of the exposure parameters with less sensitivity.
In effect what you've done is reset/recalibrated the meter by using exp-comp in Manual mode.
if you're wondering why you would want exposure compensation whilst in Manual mode .. again it comes back to the gear used(eg. lenses).
Reply With Quote
