Hi again, Margus
If you say you need a meter for use on the road then I'd go for incident reading meter every time, although that usually means the ordinary reflected light type of meter with the appropriate adaptor. I would consider a spotmeter a heavy and expensive luxury for use on the road. Having said that, of course, if you have a spot-metering option in your Medium Format (some Hasselblads, including the H1 and the 645 Contax I believe have them built in) then use that by all means.
Since you say that you will be using slide film then myself I would definitely go for incident rather than reflected metering, the thing is with slide you only get the one chance, it just doesn't have the latitude of negative film and metering errors cannot be compensated for at the printing stage. Incidentally, err on the side of under exposure with slide film, once the highlights are burnt out then there's nothing left in them to work on, whereas there's some chance of of detail lurking in the shadows if you do under expose.
As AliBaba says the incident meter shows how much light there is on the subject: set the exposure to this reading and both a black skinned and a white skinned person will be correctly exposed. On the other hand, were you to take a reflected light reading of the skin of a black and then of a white person then you would get two different readings, and if you were to take a picture of each with the readings obtained then on slide film you would end up with substantially the same skin tone for both subjects. Obviously, that would be just plain wrong, you will want a black man to look black and a white man to look white.
I would add that, for instance, if you are indeed taking the picture of a person, then hold the meter on the side nearest to the camera of the subject with the meter pointing halfway between the camera and the main source of light.
Another situation where incident metering is more appropriate is when you take a picture of somebody with their back to the sun, i.e. with their face in the shadow. If you take a reflected reading of the scene then you will get a reading that will be far too high because you are pointing the meter partly towards the sun, and if you set the camera to this reading then the subject's face will be underexposed. If on the other hand you took an incident reading with, as I said, the meter pointing halfway between the position of the camera and the main source of light (i.e. the sky in this case-not the sun, since the face of the subject is now in the shadow) then you should end up with the correct exposure.
As I said to you in another thread I'm a wedding photographer, I have both a Minolta Flashmeter V costing £600 to £700 (around 1000 Euros) (well it did when I got it) and the far cheaper Sekonic F328(?) which cost £60 (100Euros) at a guess. They both have an incident reading adaptor. The fact is, I hardly ever use the Minolta, I've got to know the Sekonic, side by side they give me practically the same reading anyway. So if money is an issue then I'd definitely go for a modestly priced meter and get to know it.
[This message has been edited by John Roberts (edited 06 November 2004).]