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brainiac
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> You can fix any of the 3 variables in the equation to a set number (the independent variable), and the remaining two variables will be the dependent variables (move one up, the other goes down, etc).
I don't think that's correct. The fixed variable, or constant would be the 'control variable', by my understanding, while the input value would be the independent variable, and the ouput value would be the dependent variable. That way, changing the input/independent variable gives you a determined result in the ouput/dependent variable. That's the only way you can make the dependent variable depend on the independent variable. With formulae, the goal is always to determine an output.
> Richard's argument is based on the sensor area being the independent variable.
No - the reverse. My argument is based on regarding area as the control: pick any two sensors of the same size (and technological maturity), and you will see that density (the independent variable) makes little difference to image noise (the dependent one).
If you want to regard size as the independent variable, then you could say that changing input size has a dramatic and exponential effect on image noise (the dependent), but that's not exactly news.
> You could also arrange the equation to make the sensor area the dependent variable, and fix the resolution (the independent variable). So as sensor area decreases, pixel density increases.
Your definitions seem confusing to me. I think in this case you might regard the number of pixels as the constant, since you have set it not to change. Regard the area and density as the independent and dependent variables. If you enter a value for the area, then area is the independent variable, and the ouput, a density, would be the dependent variable. You could also enter a density to find an area, in which case the roles would be reversed.
Frankly, I don't think it makes sense to regard any of the three variables as dependent. Here's why, from the wikipedia page that you linked to, but seem not to have read:
"The independent variable can be changed as required, and its values do not represent a problem requiring explanation in an analysis, but are taken simply as given. The dependent variable on the other hand, usually cannot be directly controlled."
For that reason, like I said long ago, all three variables are best regarded as independent variables or constants, and the dependent variable is perceived noise per square inch of 10x8 print.
Also from the wikipedia page you linked to: "Controlled variables are also important to identify in experiments. They are the variables that are kept constant to prevent their influence on the effect of the independent variable on the dependent. Every experiment has a controlling variable, and it is necessary to not change it, or the results of the experiment won't be valid."
So clearly, in your equation, you can't have two dependent variables.
Once again, just semantics.
Semantics make most statements right or wrong. More importantly, semantics determine whether you are understood by others.
> But what does this have to do with the topic, which is "high ISO"?
A great deal.
> That just depends on whether or not you believe pixel density affects noise. And I guess the jury's still out on that one...
Nobody is saying density has no effect at all on noise. The point I have been trying to make, with the support of your own kindly contributed images, is that density is much less important than other factors, like size, and if you use it as an indicator, you will often guess wrong.
ChrisDM wrote:
The equation I'm referring to, which I clearly stated many times, is pixel density.
Pixel density= number of pixels / sensor area
Which of those is a dependent variable? The equation contains no constants, so all three variables are independent. For one variable to be dependent on another, you need to define the third as a constant. You have omitted to do that, so density is independent of area in your equation. Setting sensor size does not determine the density. Since we have been discussing 21, 12, 10 and 6 megapixel cameras, it does not make sense to set number of pixels to a constant, and so density does not depend on area, as you claimed. I don't think it can be put any more clearly, so that's the last time I'm going to say it.
Edited on Aug 20, 2008 at 06:28 AM
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| Aug 20, 2008 at 06:17 AM |
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Honestly, there is so much BS on gears forums, good grief...I wonder why I bother.
More photos, less talk. 
