Dynamic Range of A7R II at base ISO?

[mandonbossi]

I am the owner of a new A7RII after upgrading from the original version and am just wondering if anybody had seen the DXO chart of dynamic range relating to this camera....

Sony A7R II : Measurements - DxOMark


So it looks to me that the ISO that delivers the best dynamic range is below what I thought the base ISO is (ISO 100)?

It is a little vague from the chart as to what that is but my guess would be an ISO of 64.... What do you guys think?

 

[GrahamWelland]

It would seem that DXO and Sony disagree on what ISO 100 actually is. The same is true for the other ISO settings according to the DR chart. If you hover over the ISO 100 point DXO say it's measured at 74 ISO and with a DR of 13.9 EV.

 

[ErikKaffehr]

Hi,

DxO uses a method for measuring ISO based on sensor saturation. Almost all camera makers give a little bit higher ISO sensivity, this can be seen as adding a bit of highlight protectition.

So the camera delivers it's best DR at ISO 100 but that ISO is measured to be 74 by DxO.

This may be an interesting alternative resource: http://www.photonstophotos.net/Charts/PDR.htm

In the charts above Bill Claff uses "Photographic DR" which is normalised differently from DxO-mark and is based on higher SNR than DxO-s DR. Bill plots against nominal and not measured ISO, which makes makers who "cheat" much with ISO to look good.

Best regards
Erik

It would seem that DXO and Sony disagree on what ISO 100 actually is. The same is true for the other ISO settings according to the DR chart. If you hover over the ISO 100 point DXO say it's measured at 74 ISO and with a DR of 13.9 EV.

 

[GrahamWelland]

Happy to see that my Phase One IQ150 blows away the A7RII on this method of measuring at least :thumbup: (which btw matches my experience - ok, we all want our best gear to be, well, best ).

 

[ErikKaffehr]

Hi,

Yes it does and it should do that as it has 70% more sensor surface, and uses Sony's sensor technology.

On the other hand, it also blows away the Pentax 645Z at higher ISOs which almost certainly depends on IQ 150 claiming higher than real ISO values.

DxO mark published a very high DxO-mark value for the Pentax 645Z but it seems they pulled it for some reason, AFAIK it was 101 vs 98 for the Sony A7rII. I have no doubt the IQ-150 is a great sensor.


Best regards
Erik

Happy to see that my Phase One IQ150 blows away the A7RII on this method of measuring at least :thumbup: (which btw matches my experience - ok, we all want our best gear to be, well, best ).

 

[GrahamWelland]

I did wonder why the Pentax didn't render similar performance to the IQ150/250/350 since in theory at least the chip is the same, even if the processing is somewhat different. I didn't see these over at DXO where I know that they literally measure the sensor vs the entire imaging pipeline. Personally, I only care about the end result from the imaging pipeline ... as that's all I ever get to see.

 

[ErikKaffehr]

Hi,

On the Sony sensors, the pipeline is enbedded on the sensor itself. That is the main reason the output is so good. So, I would be pretty certain that the raw file is essentially indentical.

On the other hand, the IQ-150 would probably used with Capture One and the P645Z would be used with some other converter.

Not least, the you can put the IQ-150 on a technical camera, hardly possible with a P645Z.

Best regards
Erik

I did wonder why the Pentax didn't render similar performance to the IQ150/250/350 since in theory at least the chip is the same, even if the processing is somewhat different. I didn't see these over at DXO where I know that they literally measure the sensor vs the entire imaging pipeline. Personally, I only care about the end result from the imaging pipeline ... as that's all I ever get to see.