how to tell if something is over/under exposed

[thebeginning]

is there a certain way to know? i always thought that over exposure was when certain parts of the photo were so bright that detail was lost and underexposure was the same except opposite (haha ?).

 

[Unimaxium]

Overexposed = things are too bright
Underexposed = things are too dark

lol

Honestly it's really subjective. A part of a photo can be under- or overexposed if it is darker or lighter than it should be, or if it is so dark or bright that detail is lost. But the line of how a part of a photo should be exposed is of course not a definite one.

 

[thebeginning]

that makes sense

 

[Christie Photo]

My old brain tells me it's all realitive to 18% reflectance. The old rule of thumb was "expose for the shadows, print for the highlights."

Lately, what I do is open the image in photoshop, select the "important" part of the image (for instance the face in a portrait), and take a look at the "levels." This lets me know if I'm close or not.

I hope this helps.

-Pete

 

[Hertz van Rental]

But the line of how a part of a photo should be exposed is of course not a definite one.

With film there are, in fact, strict technical guidlines on exposure - read up on sensitometry.
The aim is to get 'perfect' exposure, using film to it's optimum. This requires total technical control.
Once you have total control then you can decide wether you want an area to over or under expose - and by how much. This is the principle behind the Zone system.
Getting over or under exposure without technical control is called 'a mistake'.
Don't forget that with film over or under development can give the same results as over or under exposure. To decide which one you've got look at the edge markings. If they are fine, it's exposure. If they are thin or heavy then it's development. If they are missing altogether you probably put it in the fix first (I've seen it happen with students' work more times than you would credit).