EXR Confusion not fully resolved

Started Jan 25, 2014 | Discussions thread
photoreddi Veteran Member • Posts: 7,973
Re: Here's The "Party Trick" Explained

Trevor G wrote:


I originally said, and am happy to repeat it here, that the EXR sensor has no more inherent dynamic range than any other sensor.

In M size (EXR Hardware):

By splitting it (the sensor) in two and taking two simultaneous but different-duration exposures using the two discrete "half sensors" and then combining them in-camera in the same sort of way that HDR images are produced, Fuji achieve a much greater (2EV) highlight retention ability than a standard sensor.

In that way it's a "party trick" in that you can get the same result by taking two separate exposures, 2EV apart, and combining them later on in HDR software.


You've changed your tune, that's not what you wrote a couple of months ago.

An EXR sensor has no more intrinsic dynamic range than a non-EXR sensor. The only thing that is affected by EXR is JPEG output, and that still won't exceed the dynamic range of a correctly exposed RAW.

What Fuji's EXR DR does is give 1 to 2EV of extra highlight headroom when shooting RAW, if you have a high contrast scene that will expose above +0.3 to +0.5EV, and you are shooting at M size with ISO less than DR.

It still doesn't lift the sensor's "well capacity" (I think it is called) and it still doesn't lower the noise floor. I believe that it's just another "party trick". And here is how to prove it:




Saying that it's a "party trick" because it can also be done with any camera using "two separate exposures..." shows how well you're able to twist words. As originally written, your "party trick" trivialized Fuji's substantial EXR DR achievement. Most people reading what you originally wrote wouldn't think that much Fuji's EXR DR if they thought of it as only a "party trick", and would miss the point that being able to increase a JPEG DR by one or two stops was an amazing achievement, not matched by any other non-Fuji small sensor camera. When the F200EXR was introduced, there was no other compact camera that could approach or equal the JPEG DR of some DSLRs. Some "party trick".

You're also completely missing the point by writing "It still doesn't lift the sensor's "well capacity" (I think it is called) and it still doesn't lower the noise floor." It's not important that the well capacity isn't increased and the noise floor isn't lowered. What's important is that in the shadow regions of the photo, the SNR (signal to noise ratio) is increased because the exposure can be increased in the dark regions of the frame by up to two stops (the noise floor being the same) without increasing the risk of blown highlights, because those potential blown highlights are shot with the other half of the sensor using a shutter speed that's either two times or four times faster.

With an increased SNR, the same noise is still there, but it's masked by the much brighter shadow areas that are not only brighter, the tonal range and color vibrancy in those areas is increased. It's the same reason why photographers seeking the best image quality try to ETTR (expose to the right) and audio engineers and purists recording to magnetic tape try to increase the gain as much as possible for the content that has the highest volume (sound level) without producing distortion (somewhat akin to blown sound 'highlights'). It increases the SNR, making background noise/hiss much less noticeable during quiet passages.

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