@dolina: You're right, there are instances where the scene's dynamic range (SDR) exceeds the camera's dynamic range (CDR). For example, shooting landscapes on a very sunny day. If you were to expose for the sky, your ground would be underexposed and if you were to escape for the ground, then your sky would be overexposed. The solutions would be either to use ND# filters or take bracketed exposures and use HDR software to merge.
You may disagree with #20 but it's up to you and I will not try to change your mind, free will and all. As I've said, the slides are based on what Ansel Adams and his peers formulated.
@yel.Imba: I didn't say that trial and error per se is wrong. My message was if someone was going to teach another person something, then it should be based on correct knowledge. Sayop siguro ako wording na 'trial and error exposure' basin mas sakto 'teaching people to learn exposure via trial and error is wrong, in my opinion." Sorry about that.
Let me elaborate what the YouTube video is teaching.
1. A photographer goes out on a snowy day and shoots a scene in front of him (let's assume the camera is on aperture priority). He takes a shot and previews the photo. The snow isn't white but grayish (assuming the white balance is correct too).
2. He then remembers the YouTube video and switches to manual. He plays around with the shutter speed. He;ll probably use a slower shutter speed and eventually he'll see white snow.
3. Now this is well and good with a DSLR but what about those with film SLR that doesn't have an LCD?
If the photographer already knows to put his exposure indicator at +2 when shooting snow, he could have avoided a lot of steps.
I do agree that he could do trial and error and say, "What if I want my snow brighter or detail-less or what if I want a dreary scene?", then of course by all means, the photographer can under or overexpose.
Also, in time, using trial and error, one may gain the intuition to adjust the EV and get the correct exposure and that's that.
Before I knew the Zone System, I really had to spend a lot of time correcting the exposure with Photoshop. Now, I still do spend some time with post-processing but only in seconds rather than the minutes it took before.
The intent of this thread is to express my opinion that a teacher should use solid knowledge when teaching others. I mean lisod man pud guro kung kung mangutana mo, "Sir unsa ISO ako gamiton?, then inyo teacher mutubag, "Ah, kana, kung hayag gamita pinaka-gamay, kung ngitngit, gamita pinaka-dako?" "Pero sir, unsa na number lagi?" "Trial and error lang bai." "Pero sir film man ni ako camera."
The professional photographer who taught me photography said that I need to learn the basics first, follow the rules before I could break them. I think it was sound advice.