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

[JR]

The Canon guy on the 1DX information videos covers the definition of native and expanded ISO.

By looking at a group of images with software, they reach a conclusion as to how 'clean' an image is, with regards to noise. If they can consistently achieve those clean results with noise levels that are acceptable low - then it is called native. If it is not, then it is called expanded - even if quite a few people may consider it as acceptable.

http://cpn.canon-europe.com/content/education/technical/eos_1d_x_cmos_sensor_explained.do

Click on above link to get the full blurb off Canon man...

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...

[Jettatore]

Any data what range one should stay in between on a 7D and also for a 5D Mark II?  if there is a determined optimal number to work with in general, I'd like to know what that number is as well for those cameras.  Even better would be some method to figuring this out for any camera.

Noise is subjective.  Some people think there's too much in an ISO 800 image from a 5DII.  Others think ISO 6400 on a 7D is usable.  The method to figure out an acceptable range is for you to take a bunch of pictures with different ISOs in different lighting conditions, then decide for yourself what is an acceptable range. 

On newer camera models (60D, 600D, 1D X), you can then do something about that - you can set auto ISO to the range that you personally find acceptable, rather than Canon's idea of what's acceptable.

Thanks Neuro.  I already sort of do that.  I was just under the temporary impression from what I was reading in this thread, that if the native ISO maxes out at say, 1600, then you might as well not use 3200, shoot at 1600 instead and then adjust exposure in editing to match what 3200 would have given you....

[Picsfor]

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!

[Edwin Herdman]

If you've got a good sense of humor, this might be useful:

http://photography-on-the.net/forum/showthread.php?t=1081982&highlight=numpty

[jrista]

Native ISO is amplified with an analog electronic amplifier built into the camera hardware, where as "Expanded" ISO is digitally amplified...as if you upped the exposure during post-processing with Lightroom. Unless you shoot JPEG, using expanded ISO offers zero benefit, as you can usually coerce better results with RAW+post processing.

The 1DX has a native ISO of 52,100, that is an electronically amplified sensitivity. From the specs, it sounds like that 52,100 ISO is supposed to be as good as prior ISO 6400 or so. If true, that would mean Canon has SIGNIFICANTLY improved their signal amplification and greatly reduced the electronic noise floor (which is amplified right along with the rest of the signal, which is one of the key reasons why high ISO tends to have greater noise.) Also if true, it would mean that if you accidentally underexpose a shot at a more "normal" ISO, you should have FAR more headroom to fix the problem without getting too much noise during post-processing.

[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?