Dear Sir,

The article on choosing between APS-C and full frame (The Full Frame Decision, April, pg 54) was interesting but seemed to minimize low light performance. As shown by the attached, the difference between a Nikon D300 and a Nikon D700 is no small matter. Low Light ISO is defined as the maximum ISO providing at least 30 dB signal to noise ratio. For the D300 the number is ISO 679 for the D700 the number is ISO 2303. This is not minor, this is a blowout. This is not my only criterion but it is an important one for me. That said, it must also be said that I will be saving for a lot longer than I thought for a new camera.

–Paul Wille

DxO measures the performance of the sensor through its RAW data. Our tests provide a more real-world measure of the camera’s performance as a system, along with the software that ships with the camera. The “definition” of Low Light ISO applies to DxO’s tests, which ignore the processing of the image and therefore measures something that no one can actually use.

In our tests of these two cameras, after processing the RAW images with Nikon’s RAW converter, we saw about one stop of difference in the noise results in favor of the D700 at the D300’s highest ISOs of ISO 3200 and ISO 6400. This is to say that the D300’s noise score of 1.4 at ISO 1600, basically matched the D700’s score of 1.3 at ISO 3200. The D300 scored 1.95 at ISO 3200 in our test, nearly matching the D700’s score of 2.0 at ISO 6400. Finally, the D300’s score of 2.83 at ISO 6400, closely matched the D700’s score of 2.8 at ISO 12,800. At ISO 800 and below, though, the two cameras showed very similar results.

If low light shooting is that important to you, then yes, it makes sense to save up and go for the D700, but that’s a personal decision. We think that DxO Mark’s score does Nikon a little injustice in that it throws out the window the exceptional job Nikon has been doing in noise reduction of late both through their cameras’ internal processing, and through their RAW converters.

If you are using the RAW data without applying noise reduction during conversion— and the only application we can think of that does this is HDR— then the DxO Mark Low Light ISO score makes more of a difference, but given the nature of HDR, you should be able to shoot at a lower ISO to begin with to mitigate this situation, thereby once again rendering the DxO Low Light ISO score hypothetical when it comes to real-world imaging.
—Phil Ryan
Techincal Editor