Demonstration of X-Trans Under-the-hood RAW Spatial (Noise) Filtering

tradesmith45 wrote:

Some of us over in the Astro forum have been taking a close look at some Fuji camera sensor characteristics. For those of you who don't follow this, astrophotographers have been discovering under the hood RAW data filtering in many Sony sensor based cameras. The well known star eater problem has been found in some Sony & Nikon cameras. An algorithm is applied to find and remove hot pixels & it frequently mistakes stars for hot pixels. Fuji seems to be doing something different.

An avid astrophotographer asked about the performance of the X-T3 & this sparked a very revealing group examination. The reason I posted here is these findings may explain the waxy/wormy artifacts & RAW converter choice/settings frequently debated in this & other Fuji forum. A star field provides an excellent way to examine these questions.

We've found that Fuji applies filtering to X-trans RAW data in camera that slightly smooths images & produces some star color artifacts but no filtering is used in the Bayer sensor X-T100. This is easily seen by comparing X-T2/3 images w/ X-T100 images. The later is much sharper. Ironic isn't it?

For many/most users & for web display, the difference will not be noticeable. And the filtering seems to only apply for longer than 5 sec. exposures.

The differences between RAW converters handling of X-trans is trivial compared to the difference between X-T100 & X-T2/3. There is no way to turn the filtering off & Fuji has never disclosed this.

This is also how we found that electronic shutter & continuous drive modes in Fuji cams bin the RAW data down from 14 to 12 bit.

For a comparison of astro image results look HERE.

For a deep dive into Fuji sensor analysis, look HERE.

Not looking to start any war about X-trans just hoping to clarify what's going on. Hope its helpful.

While I've been clear that filtering has a subtle effect, some of the responses show I perhaps should provide a bit more context.

For astro imaging, we often say success is:

• 1/3rd sky condition
• 1/3rd capture condition
• 1/3rd post processing

Whatever the camera does, it can never be more than 1/3rd of the result. In the case of filtering found in X-trans, even less.

I have dark sky usually & moderately advanced PP skills gained from several years doing this. If you have light pollution & follow any of the numerous Youtube tutorials on how to process your MW images, filtering will have no noticeable effects on your results under any reasonable viewing conditions.

Skillfully removing LP so that dim stars will show is very challenging & there are no video tutorials on how to do that. Separating dim stars from LP also requires lots of captures for stacking. Most LP removal simply erases lots of low level data from the image. That's the data most affected by filtering. Having a big stack of images helps but it is still a challenge.  My shoot-out was done at a dark location so no LP removal was needed making it easy to show dim stars.  Your real imaging may not be in such good conditions.

Even for deep sky astro w/ lots of captures stacked & dark sky, plenty of great imaging is being done w/ filtered Nikon & Sony cameras.

I tested & posted because I thought I was doing something wrong & didn't want others to think they were too when its the camera.

Hope this helps,