3

The Nikon D7000 and Sony A55 were found to have the same sensor.

But during testing, which I understand is subjective- DxoMark (dubious reputation, I'm aware) revealed that the D7000 has a much larger Dynamic Range 13.9 vs 12.4.

Don't want to start a flame-war, the example above was just to provide some context. So ignoring make, can the same sensor technically produce different results in 2 different bodies?

6

DxO are not specifically inaccurate, but like any lab testing the methodology is important to the interpretation of results.

The result as seen in files (used to obtain measurements) is a result of the WHOLE image processing chain, not merely one aspect. Every part of the image pathway is important to contributing to the accuracy of the capture process.

For example the lens affects those characteristics of light to a huge degree before you even get to the sensor which can be driven using different sensitivity settings, it outputs to various Op Amps (to raise/lower ISO) and an A/D converter which digitise what is (at that point) an Analogue signal.

All that is before you've even hit the Digital side of the image pathway, which while output is branded as raw, there is always some level of manipulation or encoding or interpretation when it is processed to see what the figures are.

Stop worrying about it, get the camera that does the things you want it to do, that you can afford and that you feel comfortable with.

TL;DR: Not only is it possible, it's LIKELY that two different make/models of camera have different characteristics.

  • Thanks a lot! Couldn't agree more with the last words, just a bit worried since I would mean migrating systems to Sony. – Chai May 28 '16 at 18:43
  • 1
    Given that the lens lineup isn't as good for Sony as for Nikon/Canon it really doesn't make much sense to switch if you've got decent glass. – James Snell May 28 '16 at 20:20
  • Not sure I agree, there is a Sony equivalent of the lens I'm using right now. However if you're talking about the quality of Nikon and Canon vs Sigma, Tamron etc. I understand – Chai May 28 '16 at 21:58
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    Don't be so sure about Sigma, Tamron, etc. vs. Canon and Nikon. Sometimes, but certainly not always, the corresponding 3rd party lens is better than the camera manufacturer's lens. This is especially true of the more recent offerings of Sigma and Tamron. Compare, for example, the Sigma 35mm f/1.4 DG HSM Art lens to the Canon EF 35mm f/1.4 L: the-digital-picture.com/Reviews/… – Michael C May 29 '16 at 4:42
  • And IIRC, some of the DxO tests operate on JPEG images, which adds even more potential for the manufacturer messing with the data. I'm not sure about those two particular measurements, though. The biggest question is probably whether the camera is reporting ISO accurately. If not, then yes, you might shoot the same shot with otherwise identical hardware, but where one reports the ISO differently and holds the lens open a little longer to make up for it, and get different dynamic range... not to mention the question of clean gain and noise floor on the op amps, etc., which you alluded to. – dgatwood Jun 4 '16 at 6:36
3

can the same sensor technically produce different results in 2 different bodies?

I guess it could produce different results even in the same body, due to different environments. If you take an image in a hot climate, the camera will be a lot hotter, which usually means more noise and possibly a different dynamic range.

From that point of view, having the same sensor, but different bodies might cause different temperatures of the sensor during operation even under equal environmental temperatures.

On top of that, it's unclear what "the same sensor" really means. Does that include all the readout electronics? Is the signal coming from that sensor processed the same way on both bodies?

"same sensor" sounds like the hardware is the same, but it's actually just one component of a complex device. Do two cars perform exactly the same if they have the same motor? They can still have different gearboxes, electronics, tires, drivers, etc.

  • Thanks you, the answers here have made it clear to me that the pathway between the sensor to the storage has a big part to play in the image quality. – Chai May 28 '16 at 18:44
0

One thing that has impact on these parameters is density of the Bayer filter placed on top of the sensor. If two manufacturers use the same sensor but different density of the Bayer filter, there will be differences in amount of light that passes through and therefore (among else) different noise levels that I believe are essential for the DxO numbers.

That and the signal/noise ratio of the used A/D converter and amplifiers. Also there might be some noise reducing or other manufacturer specific firmware tricks in play.

-1

The Question is about the sensor not the system.

No. I think it depends more on what was done with the data from the sensor than on the sensor itself. The sensor itself has a fixed response under similar circumstances.

Disclaimer: We're talking averages/specifications as if one could actually use the same sensor by exchanging it in different bodies. In practice, NO two things or events are ever "the same." There will be variation within production tolerances for the manufactured batch/run.

  • Thank you! I think the part about what happens later is true, not sure I can validate the former part, I'm newer to this than the rest of the community. – Chai May 28 '16 at 18:45

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