EXR Confusion not fully resolved

Started Jan 25, 2014 | Discussions thread
photoreddi Veteran Member • Posts: 7,944
Re: EXR Confusion not fully resolved

Timur Born wrote:

photoreddi wrote:

No, M size pixels are not the same size as L size pixels. Pixels are (as you indicate) mathematical creations of a complex demosaicing algorithm. The photosites used to create the M size pixels are the same size as the photosites used to create L size pixels, but there are twice as many L size pixels as M size pixels so they can't be the same size.

I guess this is more a question of how we define things than how we understand them. If you take two consecutive shots on any camera and then combine them, does that increase pixel size or just sample size? There is a difference in my definition.

I take this as a non-answer.


You seem to think that to create an M size pixel, the demosaicing process has to create individual L size pixels and then average them down to M size pixels.

No, I even described it the way you describe it in the paragraph below. But language barriers surely add to the confusion. What happens is that raw data of all L sized pixels is saved in the RAW file and then adjacent pixels of same filter-color are preferably averaged *before* demosaicing.

Leaving aside that I haven't been discussing RAW files (files are the things written to memory cards) but JPEGs, this is what I wrote but which is not what you described. Maybe you think that you did, but if so, you need to be careful to avoid writing "pixel" when it seems that you were describing "photosite".



Unless you have a link to a Fuji document that explicitly states how the pixels are created, I'd have to think that the Occam's Razor principle suggests that the simpler explanation (or in this case, process), while not foolproof, provides more support for my theory than yours.

The simple explanation is that collecting the same information two times and then averaging the data leads to a higher signal-to-noise ratio, because noise happens randomly. Thus it can be expected that the chance for noise to hit the same (pair of) pixel(s) twice is smaller than just taking a single sample.

But you were talking about pixels previously, not photosites, and you continue doing that here. Pixels have already been demosaiced, and that's akin to blurring them with an AA filter. Combining/averaging two blurred pixels results in reduced resolution compared with combining the un-mosaiced dual photosites. Following this is the Bayer-ish demosaicing process that creates the final pixels. This is advantageous for M size resolution which is already much less than the camera's stated resolution, and as reviewers are wont to say, M size resolution is very good indeed.



Could you post a link to the page that has the "mp pixel" scores along with the controls that allow Screen vs Print to be selected, or describe how to get to it? All I see are DxO's bar charts showing Overall Score, Color Depth Score, Dynamic Range Score and Low Light ISO Score. This is on the Scores page. The Measurements page makes charts available that show ISO Sensitivity, SNR 18%, Dynamic Range, Tonal Range, Color Sensitivity, Full SNR, Color Response and Full CS (Color Sensitivity), but nothing for sensor resolution.

In the measurement graphs there are two buttons in the upper left corner saying "Screen" and "Print". "Screen" is the native resolution of the measured sensor, "Print" is always sampled down to 8 mp.

I've seen that control before but not here. Do you see it here?


If not, I probably was conflating you and Trevor. Speaking of whom, I wonder if you agree with his opinion that EXR sensors have no more dynamic range than non-EXR sensors, even when EXR DR mode is considered?

Is that what Trevor says that EXR DR does not provide more dynamic range over non EXR sensor of *same* size?

Yes. He calls EXR DR mode a "party trick".


Anyway, when two sensors of same size are based on roughly the same technology then they more or less offer the same dynamic range. It's all about collecting photons, turning photons efficiently into electrons and keeping read noise (of the electronic circuits) down.

No, it's usually about collecting photos, but not when the two halves get different exposures, as happens with EXR DR mode. Resolution is reduced but the dynamic range increases one or two stops worth. I'm surprised that you'd disagree with this as it was stated (with illustrations of the CFA layout) in DPR's review of Fuji's first EXR camera and repeated in subsequent reviews of other EXR cameras. If you disagree with this, you'd have to also say that HDR photography that combines individual photos show using different exposures doesn't produce photos with increased DR.


What EXR DR does in essence is nothing else than taking two consecutive exposures at lower resolution and then combine them into one. You can do the very same with every camera out there and likely get better results at same sensor size and (HR) pixel count than what EXR DR gives. The benefit of EXR is (only) that it works handheld with perfect pixel-alignment and doesn't require post-processing to merge the two exposures.

Wow. You're still not acknowledging the use of different exposures by the two sensor halves in EXR DR photos. Do you really not understand this after so much time has passed? I guess that you and Trevor both subscribe to the "party trick" theory after all.

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