Exposure Simulator

That does a fairly good job.

I'm sure that image nerds would poke holes in it, but it seems to work pretty much exactly the way it does IRL.

The noise at high ISO is where it can get specific. Some manufacturers make cameras that actually do really well, at high ISO, and high shutter speed. This seems to reproduce a consumer DSLR.

Not sure why value on the exposure compensation scale changes in manual mode when ISO is fixed. Shouldn't it be static in that case, unless ISO was in auto?

It seems to be impossible to grab the sliders on mobile Safari

This is missing a setting for the kind of light falling on the subject. Is it full open sunlight? Open shade? Overcast? Sidelight? Backlight?

It all matters.

Nice, but I'm going to need some ND filters :)

Changing the ISO appears to scale the noise differently from the rest of the image.