Both Canon and Nikon recently introduced cameras that go all the way up - WAY, WAY up - to an amazing ISO 102,400. Yes, that is ISO one hundred and two thousand, four hundred. I think my first reaction upon reading that was "whaaaaat??!?!". Of course if you do the "whaaaaaat?!?!" part in a high, squeaky voice, you'll understand my shock.
Now, consider that every full stop increment in ISO (100 to 200, 200 to 400, etc) is twice as sensitive to light as the one before. ISO 200 is twice as sensitive as ISO 100 and ISO 400 is twice as sensitive as ISO 200. As an example, if my exposure settings were 2 seconds at f/4 at ISO 100 the equivalent shutter speed would be 1/500th of a second at ISO 102,400. WOW!
That leaves me with two questions - 1) who needs that? and 2) will it be any good?
Who needs that?
I bumped in to one of my photography instructors (John Chandler - great photographer, wonderful person) at the Canon 7D release party last week. We were discussing this incredible, new ISO range. John, who has been shooting pictures as long as I've been on the planet, asked "who could possibly need that?". I didn't really have a straight up answer. All I could offer was a jesting, "well, I guess if you were shooting luminescent fish in a cave at midnight**, it could be handy". John commented that back in the day going as high as ISO 1600 was rare yet somehow they were still able to make photographs. At the time neither of us could come up with a solid requirement for such an extreme ISO setting.
I'm sure someone needs it, or will quickly find a use for it. I typically do not shoot above ISO 1600 because it is just too noisy on my Canon 40D - quality suffers. This brings us to the next question.
Will it be any good?
To try and come up with a reasonable answer first we must understand what happens when we jack up the ISO. Back in the film days increasing the ISO (it was actually called "ASA" back in the day but let's not go there) meant changing film. When you changed from ISO 100 film to ISO 400 film the recording media became four times more sensitive to light. In these digital times we do not change the sensor (duh) we just make it more sensitive. How? You just amplify the signal. That's all fine and good but when you amplify the signal, you also amplify the noise, which you can read more about here.
So will it be any good? My gut tells me that ISO 102,400 will be pretty darn noisy and unusable but both Canon and Nikon are saying quite the opposite. Gee, why wouldn't they? I guess time will tell if it is just a race between competitors (much like the megapixel race) or it is truly a practical and useful feature.
In the meantime you have to admit it is pretty crazy stuff.
**Credit where credit is due. My friend Ian Ferguson actually came up with the "luminescent fish" part. I originally said "bats". Luminescent fish is funnier.