Exposure Basics, lesson three?

Started Mar 18, 2013 | Discussions thread
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Najinsky Veteran Member • Posts: 4,931
Re: Quick correction.

Myself, I tend to think that the correct understanding is the more simple understanding:

  • Exposure is the density of light falling on the sensor.
  • Wider aperture and/or longer shutter speed means more exposure.
  • Greater exposure, larger sensor, and/or more efficient sensor means more light recorded.
  • More light recorded means less noise.
  • Sensors can absorb only so much light, beyond which you will get blown highlights.
  • Camera's ISO setting adjusts the brightness of the LCD playback and/or OOC jpg, as well as influencing the camera's choice of f-ratio, shutter speed, and/or flash power depending on the AE (auto exposure) mode you are using.
  • Image files have a limited bit-depth, so increasing the ISO may push portions of the photo outside the range of the image file, resulting in blown highlights.

Is it really that confusing?

Try it. Offer your services to a local college. Put the course together and get it approved by the college. Get them to include the course in their night class program, see if people want to sign-up and pay money for it. And if it all goes ahead, deliver the course and get a critique about how well the course was received.

It's really great fun, you meet interesting people, and it's one way to know for sure.

As it happens, I have some experience putting courses together and having them approved by colleges. I also have experience approving and accrediting courses put forward by others. Moreover I have put on photography courses for photography clubs and others. Not 'approved', but great fun, as you say.

But to give some partial answer. I believe if I submitted a beginners course with terms/equations like Total Light Collected = Exposure x Effective Sensor Area x Quantum Efficiency, the course would be rejected as having missed the brief that it is aimed at complete beginners.

There you get bemused by the vocabulary. I suspect that it is that 'Q' word, which makes people think of deep Physics. It's a perfectly simple concept, so many photons hit a sensor, how many get counted.

I think those of us who loved maths at school, and I presuming to include you in this for now, will never truly understand the fear and panic that strikes so many people when confronted by numbers and equations. Recent studies using MRI scanners have linked math-phobia to the same part of the brain associated with the fear of physical harm and pain. It's a small study, due to the cost of MRI, but not contradictory with what I see with people in real life.

I think it is truly to the shame of most nations to have produced so many math-phobic citizens. And while that's an entirely different rant, it did play a small role in the course structure.

My materia is archive on a different computer, but these from a google images search are quite similar:

The first introduction to the exposure triangle serves only to introduce the three terms and looks something like this:

From digital-photography-journey.com

But later in the course when the different values have become much more familiar, it evolves into something much closer to this as, a recap aid:

from www.wired.com

This diagram can genuinely be quite transformational for some people. Before starting the course they didn't know what any of this meant, and now they understand not only the terms but they no longer have any fear of all those numbers. And all that in just a few lessons. Had they been shown this version in the introduction, I have no doubt a couple would have fainted, or at the very least experienced a fear response in the same are as the brain as fear of pain.

I also don't really buy into the unlearning argument in this context.

It is only now, that they have got to this point, and an understanding of what all those numbers mean that they develop the confidence to start taking things further. To me, it seems a vary natural progression for the more inquisitive minds to start thinking along the lines of "dam, that ISO would be so useful if it wasn't for that pesky noise". What is this noise and is there anything I can do about it.", while the more artistically motived start playing with motion blur and painting with light.

The bird has wings and is free to fly. Free to discover and explore concepts about maximising the signal quality, shooting raw and exposing to the right.

Typical un-learing problems are of a different order of magnitude to this. They occur when something has not only been taught, but re-enforced, and it is fundamentally wrong.

There is nothing fundamentally wrong with diagram, because it does not seek to be a technical definition of exposure. It seeks to be a visual aid to three settings and the effect they have on the image that gets made.

The ISO setting and it's impact on the image is a truth they verify with their own eyes, because it's how most cameras still work. I believe it would be foolish not to start the explanation of their cameras actual operation in terms of how it actually operates from the user perspective and the actual output it delivers. Diving straight under the hood would just lose people who were under the impression Photography is fundamentally a visual art, not a technical science.

But there's only so many times we can go around this triangle. No ones going to move until the technical crowd convince the camera manufactures to abandon JPEG creation at the point of capture. I'm sure I'll know when it happens because it will be a cold day in hell.

So what do you think, are techies dismissive, aloof and intolerant? Seen any evidence of it here in the m43 forums?

Of course, some techies are, others aren't. The real 'dismissive, aloof and intolerant' attitude is 'I don't know this, so there is no reason any beginner should need to'.

Keep trying, I'm still not biting to that one

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