XFI (CMOS, 2/3" sensor) and F70exr (CCD, 1/2" sensor)

Started Jul 16, 2013 | Discussions thread
Trevor G Veteran Member • Posts: 6,570
Re: XFI (CMOS, 2/3" sensor) and F70exr (CCD, 1/2" sensor)

prime wrote:

Trevor G wrote:

You have to allow for 6 years of development in colour mapping.

Well, as the Fujifilm F70EXR was introduced only four years ago, you will have to wait two more years.

Well, they certainly made great advances in 4 years, then. I was trying to help Fuji's early rep along a little. 

You really need to use RAW to evaluate DR settings.

That would be exceedingly difficult, as the F70EXR lacks the capability to output RAW files.

Are you suggesting that there is no point whatsoever in comparing the .jpg outputs of two cameras shot under identical situations?  Then DPReview,com should simply cease operations, shouldn't it?

You probably thought I was referring to DR as an abbreviation for Dynamic Range.  I wasn't.

Instead, because this is a Fuji forum, I was referring to DR in its Fuji implementation, where DR settings refers to DR200 and DR400, which are special settings affecting highlight headroom recovery, and in particular, this effect in EXR-sensor cameras.

Since the best results from DR400 in an EXR sensor give 2.0 to 2.7EV of highlight headroom (image detail above 0EV which would normally be clipped away) but in JPEGs that headroom space is compressed into around 0.5EV of "space " below 0 EV, you cannot really see the real benefit of EXR DR settings without RAW.

With RAW you simply dial back the Exposure setting to get the full 2 to 2.7EV bnefit.

Here's an example I have posted plenty of times - as shot, image 5201:

If we reduce the JPEG exposure by 1.5EV and adjust contrast we get this - note how all the highlight information is still compressed.:

If we use Adobe products they have  good highlight recovery tools - I don't have an example to show from this image, though, but even then, because the highlight compression is not linear, the recovery tools leave colour errors.

In other words, the "recovered" image using Adobe or similar techniques such as curves manipiulation, does not give accurate colour or luminance results.

On the other hand, by taking the RAW image and simply reducing the Exposure control in RFC/Silkypix we get the full 2.7EV of highlights above 0EV returned in all their glory and with accurate colours, as here:

The final "proof" is the histogram which has been overlaid for quick evaluation.

In some cases the change in colour from trying to recover highlights from an EXR JPEG might not matter too much, but when it includes skin tones or other familiar colours we are likely to notice.

The simple solution is to always shoot RAW+, or make sure you don't over-expose when using an F70EXR or similar without RAW.

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

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