Exposure is not how dark or how light an image looks!

LOL

Here's a quote from that article: "Linear capture has important implications for exposure. If a camera captures six stops of dynamic range, half of the 4,096 levels are devoted to the brightest stop, half of the remainder (1,024 levels) are devoted to the next stop, half of the remainder (512 levels) are devoted to the next stop, and so on. The darkest stop, the extreme shadows, is represented by only 64 levels—as shown above."

That is a red herring. It doesn't have implications for exposure. The long pole in the exposure tent is photon noise, not numeric precision.

If that's true, then how to teach beginners photography is a fruitless discussion, as is the whole idea of teaching beginners photography, or teaching anyone anything. I think you are wrong about that, though.

If it's true that the majority of people don't care what anything fundamentally means, should those people really be explaining things they obviously don't fundamentally understand to others who actually want to understand? There are these things called facts and they can be pretty important, if you don't have yours straight, you probably shouldn't be trying to straighten out anyone else's.

If any group of people are trying to conduct an intelligent technical discussion, it's important that all the terminology being thrown about actually means the same thing to everyone involved or you're really all just wasting your time - Language actually matters here.

I'm assuming these posts were intended to help get everyone, especially beginners not yet misled with talk about the exposure triangle and all the other misinformation floating about, on the same page about what common terminology actually means. I applaud the effort but as we clearly see here, it's likely an impossible task.

I was watching a Richard Feynman lecture last night, and at one point he says something like: "And that's the way it works. If you find it hard to understand, or inelegant, or you don't believe it, or it makes you uncomfortable, that's tough. Go find another universe to live in."

Not 100% applicable to everything in this thread, but worth thinking about.

OTOH, was it Bohr who said: "A scientific theory should be a policy, not a creed."

At the very least, it bears out Bob's observation about how hard it is to teach someone that something that they think they have learned is wrong.

Changing ISO changes the input data the camera uses to select an f-stop and shutter speed. It's the change to shutter speed that changes exposure.

The change to ISO changes the input data the camera uses to select (in this hypothetical) shutter speed. It's the change to shutter speed that changes exposure.

no not at all, you teach them the understandings of basics, shutter speed, aperture and iso period, there is no other way because shutter speed and aperture means absolutely nothing without iso. your quote you posted "And that's the way it works" what works with just S & A ? nothing. its as bad as photo diodes and water buckets 🙄 now explain how the water produces an image 😉

For raw shooters, WRT image quality, exposure is important. ISO isn't very important. You could set your modern CMOS camera at base ISO and shoot lots of things and you'd get decent images. If it's a MILC, you might have some difficulty seeing what you're doing. You might run out of pushing capability in Lr, but there are ways around that.

Proper exposure is important. As long as there's no clipping, ISO setting isn't.

Sure, there are advantages in input referred read noise from getting to the high conversion gain setting, but they are second order effects unless it's darned dark or you have some other constraints that prevent a generous exposure.

Any attempt to teach a new photographer the basics that does not include a discussion of light, is doomed to failure. That is the most grotesque of the flaws in the so-called exposure triangle. It literally ignores light as one of the three factors determining exposure. Light is shown in the illustrations but it's not talked about. It's an inconvenient truth tucked away in the corner. But it's not discussed.

Without light, there is no photography. Without light, all we have are stories around the campfire. Light makes photography possible. The f-stop and shutter speed settings determine the intensity of light from the scene delivered to the sensor. That's exposure.

Don, if you enjoy threesomes, here's one that will put a smile on your face: light, f-stop and shutter speed. :)

I disagree, without a recording medium there is no photography, light is just what your capturing with the recording medium 😊now lets discuss "recording mediums" the crystals are the recording medium. the photo diodes are not , they capture the light the same as a microphone captures sound, but the crystals "record" the image. Now ! what part of the sensor is the recording medium ?

The image stays in the capacitors associated with the photodiodes until it is read out. It needs to be read out fairly soon because it degrades with time. So does the latent image on film, but the time scale is much longer.

The image stays in the capacitors associated with the photodiodes until it is read out. It needs to be read out fairly soon because it degrades with time. So does the latent image on film, but the time scale is much longer.

Again, the article was not written to discuss the additional topics you want to discuss; like dither, photon noise, ADC inputs, numeric precision, etc. They are fine topics to cover in a more comprehensive and in-depth book or article, but that is not the intended scope or purpose of this very brief article which is focused solely on introducing a few fundamental concepts to someone who is a newcomer to them.

The quote which you referenced is intended to introduce a reader to linear and nonlinear distribution of levels across a dynamic range with a rudimentary explanation of linear and gamma corrected distribution of image data. It is not intended to include any of a myriad of additional topics connected to the basic and narrow focus of the topics it does discuss in an introductory overview which also illustrates some of the practical implications for a novice.

The context of "implications for exposure" is the direct effect which increasing or decreasing exposure level has on linear raw levels as discussed in the two paragraphs which follow the statement you quoted and prefaced by the discussion which precedes it. I leave it to the reader to interpret the context for themselves as they understand it from their reading, but that's mine.

Readers are free to read it, draw their own conclusions, delve into additional resources to learn more, or ignore it entirely if they wish. It's only 3 pages of text and illustration, but for anyone unfamiliar with the concepts of: gamma correction; the different methods (linear and nonlinear) used to distribute levels in an image file; or how exposure affects the encoded levels of linear raw capture data; I recommend reading it as a starting point for learning more.

Yes, different people can have different definitions for exposure and most of them are incorrect. Many people see 'exposure' and 'image lightness' as meaning the same thing and then their heads begin to spin when they realise the fact that for a given scene and lighting you can vary the image lightness without altering the exposure* at all.

You are running away and cowering from posting in your own words the definition of exposure you use when you use it sentences.

This tells me you do not understand what exposure actually is, and what does and does not affect it, and how to maximise the quality of the raw data.

I post what I mean by the word exposure in my signature so everyone can see what I mean. Whether they agree with it or not is another matter and their choice to make.

No, that is not true at all for anyone who defines exposure as in my signature. Exposure* is controlled by aperture ( f-number), shutter speed and scene luminance. ISO by itself has no affect on exposure*. ISO is the very last control I set because the value of ISO is largely irrelevant as long as important highlight are not clipped because I set the final image lightness in post, not the camera.

In manual mode you can adjust the image lightness while leaving the exposure* constant.

Post in your own words the definition of exposure you use when you use it in sentences.

I always set my exposure* independently of ISO. ISO is the very last setting that is set either by me manually or the camera with Auto ISO.

* exposure - amount of light striking the sensor per unit area while the shutter is open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

It looks to me that you have been confused by the red herring in the paper, making my point. Precision is not the issue in exposure with today's cameras. Photon noise is.

Here's what Ansel Adams has to say about the definition of exposure in The Negative:

"The term exposure requires a definition. As our discussion of apertures and shutter speeds indicated, we can give equivalent total exposure to the film using relatively high intensity of light for a short time, or less intense light for a longer duration. Stated as a formula this relationship can be expressed:

Exposure = Intensity * Time

Thus, the same total exposure will occur if we increase the intensity of light reaching the film while reducing exposure time proportionally. Opening the lens aperture one stop doubles the intensity of light at the film plane; if the shutter speed is then reduced by one-half, no net change of exposure occurs. Similarly, we can reduce the intensity by closing down one stop, and compensate by doubling the exposure time."

Did AA not understand? I think he did.