cainn24
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Veteran Member
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Posts: 4,892
Re: They don't test raw "data"
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walkaround wrote:
cainn24 wrote:
walkaround wrote:
TrojMacReady wrote:
ChristianHass wrote:
If you read their review the sensor gets a normal ISO score of 506 which is basicly the same as the other 1" sensors. It's only in their "superraw" mode it gets 1657.
Superraw basicly means that the camera takes 4 shots and averages them out to reduce the noise, so it's not going to work for anything moving.
Sony RX100 also has multishot NR, but DxO didn't test that. If they had it'd probably get a similar result.
Sony's version doesn't work in RAW and they test RAW data, before demosaicing, gamma curves, color profiles etc. are applied.
DXO doesn't say anywhere on their site that they test raw "data" before demosaicing, etc.
"All sensor scores reflect only the RAW sensor performance of a camera body. All measurements are performed on the RAW image file BEFORE demosaicing or other processing prior to final image delivery."
from: http://www.dxomark.com/About/Sensor-scores
Ok, I missed that one statement, thanks. But it seems to be contradicted in other places on the site, where they mention "raw image" over and over. Not "raw image file", but "raw image". I don't think this is splitting hairs when talking about a scientific subject. There is actually no such thing as a "raw image". Canon CR2 and Nikon NEF files are not images. You can't view them in any way until they are either converted, or their embedded jpegs are displayed. So are dxo just sloppy with their website copy?
In the "About DXOMark" section, they say this about their tests:
"All published DxOMark measurements have been made using DxO Analyzer.
DxO Analyzer includes the following three key elements:
- A dedicated camera testing lab specifically equipped with dedicated test targets, lighting systems, light-boxes, light-meters, telemeters, spectrometers, etc.
- A set of precisely-described and bias-free test protocols for each measurement category which:
- Strictly accounts for all physical parameters that influence measurements.
- Ensures repeatability of the measurements.
- Software that automatically analyzes test target images, performs quality controls, and reports all measurements in graphic and data formats.
The basic protocol for all measurements is:
- Adjust test targets, lights, and the selected camera and lens.
- Shoot a set of images of the target at different camera and lens settings.
- Process the target images with DxO Analyzer (machine vision algorithms enable automatic processing).
- Evaluate the data and graphs reported through the DxO Analyzer interface."
This is as clear as mud. "Process the images" sounds like conversion to me. If they were testing data before demosaicing or other processing why wouldn't they just say "DXO Analyzer tests the raw file data"?
No one said that DxO Labs isn't analyzing image data. I think what you're missing is the fact that image data exists even before demosaicing takes place.
Here, have a quick read: https://en.wikipedia.org/wiki/Demosaicing
The reason they do this is presumably because there is really no such thing as a standardized demosaicing method, and different methods can impact slightly upon noise. Generally the differences are insignificant for the most part but DxO Labs are simply trying to work with data that is as "raw" as possible.
They use raw files straight from the camera, and do in fact convert them to "images":
Well, of course. But RAW files straight from the camera aren't demosaiced. That's something that most RAW converters automatically do when you open a RAW file. Most of the popular ones also automatically apply a colour profile, a tone curve, some lens corrections and sometimes a bunch of other tweaks as well. But it's perfectly possible to analyze the RAW data before all of these things take place, and that's what DxO Labs do.
How is it "perfectly possible" to analyze proprietary data for dozens of different manufacturers' raw sensor data? Image sensors don't all record data in the same way, in the same format.
Get a RAW file. Open it in RawTherapee, or RawDigger, or any number of other similarly capable apps that support the RAW format in question. Disable demosaicing.
Done
The reason there is support for "proprietary" RAW formats in third-party applications is because someone reverse engineered them.
And demosaicing isn't some add-on post process, it's intrinsic to the output of the camera.
It's only intrinsic to JPEG output, not RAW output. Again, a RAW file straight from the camera is not demosaiced.