Thank you very much for such a warm welcome. Thank you for all your answers. Each of them brings some more light on the subject.
I’m aware of exposure triangle, I understand the concept of 18% grey and how the camera sees the world by its sensor. I catch how values in my view finder change and I get how to set them to get my desired results. Well, more or less, but it’s been three weeks with DSLR. I'm still doing my homework, reading a lot and experimenting with my Pentax.
I've just read your answers and brought my camera to check your ideas. I think I get it now
Originally posted by bertwert It's effectively setting the new 0 on the exposure meter.
Thank you for the simpliest and the most accurate explanation. So now, I understand EC like this: I want to take a photo. I set desired mode in the camera. I find the perfect composition. I set values of shutter speed or aperture as I need for taking the photo. I shoot first photo. If it's too bright -> EC for - / if it's too dark -> EC for +. Then
I have my reference point on how I want my balance of low, middle and high tones to be like. And now when exposure is set as I want, I can manipulate with depth of field or freezing movement etc. as I want. And my camera has its reference point of exposure. "The new 0". I told the camera "Hey, I want exposure that way, I don't care about your perfect grey. Here's my perfect grey and you better stick to it.".
On the other hand, when I take the photo and exposure is good for me. Then I don't need to adjust it, do I? I do it only when the output is too dark or too bright?
Originally posted by swanlefitte I believe that is your confusion. Are you sure about that? It only changes ISO for me and only within the set range.
Yes, you're right. I checked it second time. I must've got wrong. It surely changes only ISO.
One more thing. I checked how EC works in M mode. Generally, in M mode I can see EC line in viewfinder. It indicates over or under exposure. I set aperture, shutter speed, ISO to reach the middle point "0" on that line. Right? Then If I want to, let's say overexpose by +2, I hit the EC button and dial +2. From now, the camera knows that I want brighter picture. I still need to reach "0" on the EC line in viewfinder. But when I reach "0" the photo would be brighter than before I changed exposure by 2 steps. Am I right?