[wim]

[quote name='Brightcolours' timestamp='1316942477' post='11829']

I know, Wim. Thanks for you post.



Markus and Rainer appear to be missing that with film, its ISO rating was based on its grain size, it actually had to do with how sensitive the film was. With sensors that simply is not the case.



So where with film ISO was about how to correctly expose different films, with sensors it has lost that meaning totally. It is just a big equalizer with variable amounts of amplification of the actual exposure.



Equivalent ISO settings is just like talking about equivalent focal lengths. The lens does not BECOME 400mm, it still has a focal length of 150mm. It just achieves the same, so equivalent. Same with equivalent ISO settings. They do not BECOME a different ISO setting, they simply achieve the same thing.

[/quote]

Yes and no, if you dont mind me saying.



Essentially, SNR changes, and DR changes, bot'h to a higher or lower degree, unless one really reaches the point where the sensels can't really capture enough photons anymore, and it becomes an amplifier gain only (with sharply decreasing DR and SNR). However, that is no different than it was with film. High sensitivity film has a low SNR, and a low DR, just like it is with sensors. Similarly, one can push film, or pull film, up to a certain degree, just like with sensors. The difference is that sensors, especially the slightly larger ones due to larger well sites and good SNRs, generally have a much wider latitude than film ever had.



IOW, although there is a basic, sensor inherent ISO level, if the DR is, let's say, 10 stops at base ISO, and it still is about 10 stops at 3200 ISO (example only), it is like having at least 3 different films loaded at once in our digital cameras (low, medium and high ISO). And with films, pushing a 400 ISO film to 1600 ISO, doesn't make it a different base ISO either. It just increases noise, and lowers DR, in order to capture an image.



To me it is much of a muchness, although I prefer the extended range a digital camera has to offer. In the end, the amplification of the sensor signal still makes for a correctly exposed image when using a handheld lightmeter, set to the same ISO as the camera, as was the case for our underexposed and overdeloped (hence amplified signal) film.



Kind regards, Wim