Why a Difference in Exposure between cameras?

[jpgentry]

I have just purchased a 5dm2 to replace my 1dsm2.  

I set both up on a tripod (gone through the process twice) and set manual mode with the ISO to 1600/Ap to 8/Shutter to 1/100th.  Each time I try the test with the same lens and settings the 5dm2 is underexposed by one stop and the 1dsm2 is right on the money.  

I'm happy for the slight decrease in noise at 1600 but not happy if the camera doesn't collect the same amount of light.

Can anyone explain?

-Jonathan Gentry

[Hank]

How's the noise when you open it up one stop to compensate?  Makes me suspicious how they achieved the noise "reduction."

Other than that, I expect variations of 1/3 stop between cameras of the same model, but send them back to their mama if comparison reveals half a stop difference.  We use multiple cameras and simply can't afford more variation than that.

[Panopeeper]

Questions:

1. Have you done it with raw or JPEG?

2. If raw, which raw processor?

3. Did not you forget HTP On on the 5D2?

[bjanes]

I have just purchased a 5dm2 to replace my 1dsm2.  

I set both up on a tripod (gone through the process twice) and set manual mode with the ISO to 1600/Ap to 8/Shutter to 1/100th.  Each time I try the test with the same lens and settings the 5dm2 is underexposed by one stop and the 1dsm2 is right on the money.  

I'm happy for the slight decrease in noise at 1600 but not happy if the camera doesn't collect the same amount of light.

Can anyone explain?

-Jonathan Gentry

It is likely that the cameras are using a different tone curve, since the ISO ratings of the sensors are similar as shown on the
DXO web site. Click on the ISO tab to see a graphical comparison. I would suggest looking directly to the raw file with a program such as Rawnalize.

[jpgentry]

I was shooting RAW and viewing in lightroom 2.5.

Thanks for your help guys.  There was not enough between these cameras so I returned the 5d2.  I took quite a few images and think the 5d2 has a slight advantage but not enough to overcome the handling advantages of the 1ds2.

-Jonathan