Re: ISO for beginners

This puts the cart before the horse. The more photons you can get counted the better. You'll maximize DR and lower the noise in the image.

Simply setting the camera to base ISO and leaving the exposure the same as it was at a higher ISO won't help the DR and the noise, unless the high-ISO exposure was already clipping.

I think that the CFA is in front of each photosite, and that pixels are a construction of the neighboring photosites to arrive at a more precise RGB value for that physical space in the frame.

I'm thinking the purpose of this thread in particular is to fine-tune whatever becomes the default explanation used at this website. I also think this would be a useful way to proceed with all the topics we want to include in a DPR Beginner's Primer.

And clipping.

And cross-talk, by splash. 🙂

Eric Fossum calls the light-sensitive, charge storing, buffering thingies in a sensor pixels, and that's good enough for me.

And ISO.

I was being deliberately simplistic, to counter the very technical replies on this thread. I did that because this thread is entitled "ISO for Beginners" and its posted in the "Beginners Questions" category.

In this context, I'd ask everyone to consider if they're meeting those objectives for beginners? Or maybe getting a tad too technical? Maybe there should be a separate section for advanced theory and practice?

I'm fairly sure nobody wants to scare beginners away from signing up :)

We have seen how to explain ISO in a simple and incorrect definition, as well as in a complex and correct definition.
For beginners, we must have a simple and correct definition of describing ISO. In my (short) teaching experience, this often works only by omitting details.

Simple is good. Simplistic -- treating complex issues and problems as if they were much simpler than they really are.-- is not. We do beginners no favors if we say things that are wrong in the service of making the result simple. They will have to unlearn that stuff later.

And, in this case, the right explanation of exposure is simple, and it doesn't involve ISO. I sometimes liken the ISO knobs on cameras to the plastic steering wheels that you stick on the dash with suction cups so your kid can pretend he's driving. A bit over the top, but it gives the idea. For raw shooters, the ISO control can't do much good, but it can do great harm.

Yes I hear you and I agree..... to an extent. I still stand by my central point though. This thread has gotten really quite technical. Yet it's aimed at beginners. Maybe we all need to step back for a moment and get back to explaining the basics when aimed at beginners.

An analogy:

If I buy a new car and it has a button I don't understand, I'll look online for the answer.

Do I want to learn what that button does? YES

Do I want an answer that includes a wiring diagram for the car, a lesson on ohms, amps, volts and relays? NO :)

The quest for a simple and correct definition is made more difficult by the fact that there are so many ways to implement ISO changes, and they all have different effects on photography. In the GFX 50S, I'd say do one thing; in the case of the GFX 100S, I'd say another. An Fuji is not transparent about their implementations.

I think you're confusing the sausage making with the sausage. This thread is about how to construct a tutorial for beginners. It is not itself such a tutorial.

Well its a thread called "ISO for Beginners" and it's posted under a category called "Beginners Questions". So I'll have to disagree with who is confused here Jim, sorry.

Yes, there are many ways of implementing ISO. My belief is that a beginner does not need to understand the detail of any particular implementation in order to understand the overall concept of ISO.

A car analogy might be the gas pedal. Conceptually, when you push the pedal down, the car goes faster. The further down you push it, the faster the car goes. One does not need to understand automatic transmissions, or direct drive electric motors in order to understand the concept, nor does one need to understand it in order to be a very good driver. Obviously, this doesn't tell the whole story. There is generally an upper limit on how fast the car can go, head winds, tail winds, and hills might also alter speed, even if the gas pedal is help constant. However, for someone first learning to drive, the idea that pushing down on the gas pedl makes the car go faster, is an incredibly useful overview.

Now, if you are trying to absolutely maximize some aspect of your car's performance, it can be helpful to understand what's happening under the hood. But a beginner driver does not need to know these things.

When it comes to Digital Camera ISO Speed, the absolutely correct definition is the ISO standard. That standard is careful to avoid specifying how ISO is implemented. It only addresses aspects of mapping the exposure to image lightness in the resulting image.

I think it is good start to explain to beginners that light is comprised of photons, and "exposure" is determined by the photons reaching the sensor, and I think it's useful to think of the pixels as roughly counting photons. As a general rule (and there are exceptions), the pixels seeing more photons report higher numbers.

I think it's also a fair overview to suggest that the ISO setting gives a context for interpreting those numbers. Clearly, ISO is not the only factor, as the pixel size, bayer pattern filter, and other camera specifics also play important roles.

Obviously, the above is a gross simplification. For instance, it ignores Bayer Pattern color filters which block many photons from reaching the sensor. However, my goal was not to teach someone the details of how cameras work, nor to teach them every nuance of photography. It was merely to teach the concept of how ISO influences the process that maps exposure on the sensor to image lightness in a camera produced JPEG.

Actually, one does. ISO is like the "stick" which is popular around the world, not so much in the US. Even auto transmission cars often have a manual override.

IMO, all is lost once car analogies come to the fore.