Anyone have a good explanation of "native" vs "expanded" iso?

[Edwin Herdman]

Native ISO is amplified with an analog electronic amplifier built into the camera hardware, where as "Expanded" ISO is digitally amplified...

Only some of the expanded ISO settings work solely in this way. The link I provided gives more clues.

 

[jrista]

@Edwin: Sorry, hadn't read your link. I'll check it out.

EDIT:

Hmm, I'm not sure I buy all the reasoning in that article, given that it lacks any citations. His explanation of "Numpty" ISO is analog-only gain, vs. "Smart" ISO which is simply metadata, which would force digital enhancement in some post-processing tool. He claims Numpty is worthless, while Smart is useful. There is a HUGE difference between amplifying a signal directly, and enhancing it digitally. I would take analog gain any day over digitally enhancing. I had a debate a while back about the merits of choosing the lowest ISO vs. choosing the highest ISO when shooting with someone on a forum I participate in. The merits of those two choices aside, the debate resulted in some visual examples of analog amplification vs. digital amplification that I think might be enlightening:

http://photo.stackexchange.com/a/6622/124
http://photo.stackexchange.com/a/6712/124

Farther down in the Numpty thread, he explains some of his own tests, and his own conclusions about the 5DII. It sounds like the -1/3rd and standard ISO settings up to ISO 1600 are all what he calls "Bargain ISO", and he claims they are better than ISO 3200 given that they are "analog". I can't really tell the difference between Numpty and Bargain ISO from his description, given that both are amplified electronically...but one seems to enhance noise a lot while the other only a little.

Either way, that article discusses only "native" ISO levels + ISO 50, but does not discuss the H expansion levels (12,800, 25,600). Given that he claimed ISO 50 was "Smart ISO", I would be willing to bet that both H1 and H2 are also "Smart ISO", which according to that article is simply a metadata value and therefor 100% digital enhancement.

 

[JR]

Based on this, I remember from the 1DX announcement that they marketed its "native ISO" as 51,000. Does this mean Canon feels ISO 51,000 has acceptable low noise level on the 1DX...and this would compared to say ISO 6400 on a 5D mkII?

I cant wait to see real test review for this machine...

Actually, 51k on the 1DX is incredibly better at 51k than a 5D2 is at 6400. I think you would have to push to 104k to get the same result - from what i remembered of my play with one in October.

I kid you not, i was shown a print of a tube depot with the trains stabled overnight - i have similar shots taken on 100asa film - and that required tripod and seconds worth of exposure. This one at 51k was done at a hand held speed. As said before, i appreciate that Canon give this pic the treatment - but the simple fact is, it shows what it can do at 51k!

I sure hope you are right Picsfor! I cant wait to see this for myself.

 

[AprilForever]

I find the 7D 6400 ISO usable... just takes a mite of work, bit it really is epic to shoot in dim conditions when others have long ago put away their gear to slap on a 50 1.4 and continue to shoot... Focus can be frustating though...

But, concerning native ISO...

I have heard that the 7D's native ISO is 160... is this true?