Ah, a few thoughts about ISO-less

Started Jul 10, 2013 | Discussions thread
mjack101
Regular MemberPosts: 108
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Re: Ah, a few thoughts about ISO-less
In reply to bobn2, Jul 11, 2013

Bobn2 wrote:

TTMartin wrote:

HumanTarget wrote:

AnthonyL wrote:

PS - as far as I know, Canon cameras are not ISO-less... I think they are of a type where adjusting the ISO knob makes a good bit of difference. Not sure, though...

I find it makes a big difference so I assume it is not ISO-less.

You're right, Canon sensors thus far have not been "ISO-less." But they usually max out at ISO 800 or ISO 1600 (depending on the camera), and do software pushing beyond that, so there's no more benefit to increasing the ISO setting at that point. You just lose highlights more quickly. Cameras will lose 1 stop of DR at every doubling of ISO at that point.

It certainly can't take 4 stops below correct metering and be recovered (ie just turn down from 1600 to 100). Can ISO-less cameras? What happened to the analogue gain?

The reason to amplify the signal is to reduce the impact of additional noise; you can't clean up the signal you've already got by amplifying it. Depending on the design of the sensor, amplification may not be necessary.

Canon cameras may be the closest to ISO-less cameras of the future than any other brand at this time. According to DxOMark cameras like the 6D have basically no change in dynamic range from their ISO setting of 100 through their ISO setting of 800.

So fundamentally, changing the ISO setting on a Canon camera is merely moving the center point of their 11EV capture range up or down through a 14EV range.

Sorry the reverse is the case. Canons are by and large the most ISOful cameras you can get. In an ISOless camera the DR should reduce one stop each stop increase of ISO (if it had an ISO control) since the maximum signal reduces one stop while the noise floor doesn't change.

Until output mediums and a replacement for the 8 bit JPGs file format takes hold, then where you want the center point of your output dynamic range to be will have to be set. Which if you believe DxOMark, is what you are doing with Canon cameras today.

Bob2N will write:

Why wouldn't I believe DxOMark.

No, I'll just write why you've got it entirely back to front.

-- hide signature --

Bob

Bob is correct, I have done a little testing with my 5dmiii and it is ISO-full until somewhere between ISO 1600 and 3200. After that it is ISO-less.

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