CMOS ISO100 vs. ISO200

I just realized a couple of days ago that the "new" generation of Nikon Cameras all have ISO200 as the lowest standard value.

They can reach an ISO100 by some calculations somehow. I assume that it is some sort of technical limitation of the CMOS technology.

So, it should be the same for the other manufacturers as well.

For UW,I am almost only using ISO100 with my D80. The reason for that (same as in analog times) better colours.

So, this confuses me. Is this not true anymore?

How does the ISO200 work in practice for UW usage with the new generation of CMOS sensors?

/Erik

I just realized a couple of days ago that the "new" generation of Nikon Cameras all have ISO200 as the lowest standard value.

They can reach an ISO100 by some calculations somehow. I assume that it is some sort of technical limitation of the CMOS technology.

So, it should be the same for the other manufacturers as well.

For UW,I am almost only using ISO100 with my D80. The reason for that (same as in analog times) better colours.

 

 

So, this confuses me. Is this not true anymore?

How does the ISO200 work in practice for UW usage with the new generation of CMOS sensors?

 

 

/Erik

It certainly isn't inherent in CMOS; Canon uses CMOS and gets down to ISO 50. Rather I think it is because the noise levels at 200 are so good that you don't need 100 at least in Nikon's view.

Nikon worked on increasing the performance of their microlens array to improve sensitivity for better high ISO performance. Higher base ISO is a side effect. It's not necessarily and advantage for UW shooting but it is what it is. What's more interesting is how manufacturers go below base ISO. New Nikons can be set to ISO 100.

Something I've noticed recently is that some cameras are starting to have hidden, default exposure compensation specified and the new Nikons are among them. I have seen this through my recent raw converter testing. Both RPP and RD reveal that Nikon is deliberately underexposing based on their published ISO and jacking it up in the converter. Perhaps part of the explanation for ISO 200 is that Nikon is hiding some highlight recovery in the exposure just like Kodak used to do.

Sorry for misssing that the Canon's can go lower.

Interesting thought if they are deliberately underexposing it.

What are you Nikon D300 users out there think about it?

/Erik

New Nikons can be set to ISO 100.

I was under the impression that when you used "LO" ISO settings on the Nikon it was effectively like using an ND filter and it did not come with any increase in signal to noise. Is that not the case?

That's correct - the LO setting yields no improvement in S-N ratio. Since it doesn't meet the ISO spec they can't call it 50 - they have to call it Lo.

James

The Canon LO setting is useless. It does not change the sensitivity of the sensor and won't help against blown highlights. All it does is change the metering and tags the ISO 100 raw file as LO. A similar thing is done at the HI setting. It changes the metering and doubles the value of the numbers in the raw data file. It dose not changes the sensor sensitivity from the highest ISO setting in the normal range.

I read a post in dpreview awhile ago where the author looked at the numerical content of a HI raw file and found it has all even numbers.

I've read that Nikon's LO setting has similar shenanigans. I just didn't want it to pass that Nikon is ISO 200 while Canon "gets down to 50". Compare apples to apples.

Some say that Nikon LO has less dynamic range than base. Others claim that the real ISO is unchanged and highlights will get blown just like Herb describes with Canon. I'm now seeing that Nikon is lying about its exposure at base ISO and hiding exposure compensation in the raw converter. This would explain why people are saying that Nikon LO only blows out 1/2 stop sooner rather than a full stop. I'm going to investigate the real clipping point of base ISO versus what the camera is telling me it is. It's incredibly annoying to have an RGB histogram that you can't use to check exposure.