70D Dynamic Range is actually great, despite what DXOMark says

Started Jan 21, 2014 | Discussions thread
janfi67 Junior Member • Posts: 35
Re: 70D Dynamic Range is actually great, despite what DXOMark says
1

TTMartin wrote:

According to DxOMark every Canon dSLR they have tested basically has the same per pixel dynamic range. That includes the original 2003 APS-C Digital Rebel and the full frame 1D X. Any changes in dynamic range scores is because DxOMark uses a formula that changes the print dynamic range score based on the number of megapixels.

So you can choose to believe DxOMark, or you can look at possible flaws that would explain these seemingly erroneous results.

There is a group here that believe the results are accurate and can be explained by noise from the external analog to digital converter, I don't believe this is correct.

Oh yes, please... prove me that my lovely Canon camera is better than DxO and other say. Explain me why they are all wrong and why the DR is far better than 11EV. I can't wait to know.

First DxOMark attempts to measure sensor noise by looking at the RAW file. This basic concept is inaccurate because manufactures can apply different amounts noise reduction prior to the RAW file being written. Case in point the Nikon D300, Nikon D300s, and the Nikon D90 all use the same sensor. Yet the Nikon D90 scores higher than the Nikon D300 and Nikon D300s, because the D90 applies more noise reduction PRIOR to the RAW file being written.

Hummm... Like all photographers, I can only use the RAW files, not the sensor output. So I only care about what the RAW file contains and what I can do with it.

And as said previously, you're wrong. D300 and D90 don't use the same sensor.

Camera that use Sony sensors apply noise reduction at the sensor level prior to the RAW file being written.

Do you think Canon doesn't apply some kind of noise reduction prior the RAW file being written? Never heard of CDS? It's embedded in the sensor itself (including the Canon ones) and it's a noise cancellation system.

Canon embeds information in the RAW file to be used by their RAW converter DPP. Third party RAW converters don't take advantage of this information. For example Canon masks portions of the edge of their sensor, to provide information on both row and column sensor noise, 3rd party RAW converters like the one used by DxOMark do not use this information.

You seems misinformed. Take a look at public domain RAW converters sources and documentation. After reverse engineering they use data provided by the masked portions of the edge of the sensor to reduce the noise.

And how can you tell than products like DxO or ACR don't use them? Are you aware of all the details about CR2 format Canon discloses only under NDA?

Third party RAW converters attempt to directly read portions of the Canon CR2 file and directly convert them to RGB. There are several problems with this, first according to Canon's Chuck Westfall Canon RAW data is recorded in sYCC and not RGB.

This is one of the funniest part of your post, and once again, you're wrong.

Do you realize what does recording RAW data in sYCC mean? I don't think so, despite the picture you post.

An sYCC encoded image is obtained AFTER DEMOSAICING the CFA RGB data. It's not a RAW format.

For your information, Canon sRAW formats use YCC encoding, but they aren't RAW format per se, and they are not used by DxO to perform their tests. It's a kind of lossless jpeg, but using 15 bits data for the 3 components, Y, Cr and Cb, not 8 bits like traditional jpeg.

So the process of direct conversion to RGB often result in unexpected results, like this CR2 image from my Canon 6D with a 3rd party RAW converter that doesn't know the 6D exists.

It seems you have no idea of what the CR2 format is, and how it differs for 6D compared to previous Canon cameras. There are many differences that can explain a RAW converter that doesn't know the 6D exists fails to convert a 6D image.

For example, since Canon 50D and digic IV, CFA RAW data are encoded in 4 components into the CR2 files. The 6D (and the 1Dx) use only 2 components. Tricky for a RAW converter, isn't it? This has nothing to do with sYCC.

Another flaw in this attempted direct conversion to RGB is that it uses the HSB/HSV color space instead of the HSL color space used by Canon.

Once again, you don't understand what you're talking about. HSL is used in Canon picture style editor. It has nothing to do with demosaicing.

So what does all this actually mean. In my opinion the Canon CR2 file has been incorrectly reverse engineered by 3rd party RAW converters. This incorrect reverse engineering has only resulted in 12 bits of usable data per pixel and not the full 14 bits. And it is this that actually explains why testing sites that use 3rd party RAW converters show that Canon's per pixel dynamic range has remained unchanged in the last 10 years and not that the 2003 Digital Rebel and the Canon 1D X have the same per pixel dynamic range.

I'm really disappointed. I expected strong evidences, solid technical arguments. But no, it was only blabla and technical words ans concepts not understood by a Canon fanboy.

By the way. I'm very happy with my Canon cameras even if they have less DR than other brands.

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