EXR - Hardware Or Software? Here's The Interesting Evidence...

Started Sep 5, 2013 | Discussions thread
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Trevor G
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EXR - Hardware Or Software? Here's The Interesting Evidence...
Sep 5, 2013

Not everyone realises that EXR cameras (those with EXR sensors, not all the rest of them with EXR processing) use the unique pixel pairing routine over a very small range of ISO values, and just in M size.  Afterall, EXR is a complicated system which has never been really explained fully by Fuji, but some clever people have worked out what goes on, and when.

I am indebted to Timur Born who set me on the right path.  I took these images 12 months ago, expecting that I would be able to see EXR hardware at work, but I only examined them the other day, while trying to help someone who was challenging the idea.

What does hardware DR do?

Two simultaneous exposures are recorded - the second is shorter than the first and starts after the first but they both finish together.    The shorter exposure is used to preserve highlights.  The 2 images are combined in the camera to produce a JPEG composite.

In DR400 the second exposure is 1/4 the duration of the first, to give 2EV of under-exposure which is then lifted by 2EV during the RAW manufacturing process to give 2EV of extra highlight headroom.  In DR200 the second exposure is 1/2 the duration of the first and processed in the same way, to give 1EV of extra highlight headroom.

In truth, the RAW output does not contain lifted highlights - there is a marker added to the RAW depicting either DR200 or DR400, and software such as Silkypix and Adobe recognise this, and adjust the RAW output accordingly.  Other software, such as RawDigger, do not recognise or respond to these markers and just display the RAW as it is recorded, 1 or 2EV down.

RawDigger has another advantage - it can pull the 2 frames exposed during hardware DR and display them, or even output them as TIF files for later processing. Here is an example:

And here is RAW Frame 2, under-exposed by 2EV:

The camera combines the 2 RAW frames into one for JPEG output, which has the lowlights from Frame 1 and the highlights from Frame 2:

And finally, the RAW output after adjustment in Silkypix:

I'll add more examples which show quite graphically the difference in exposure by time.

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Cheers
Trevor G
Silkypix tutorials at: http://photo.computerwyse.com

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