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DanBailey

Why the Fujifilm X Series Images are so "Film Like"

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DanBailey

As most of us already know, the Fuji image files look awesome. To be fair, image files from any camera these days will look really good, but there's something really special about the way the Fujifilm X Series cameras portray color and tone.

While the Fuji image processors play a part in this, much of the Fuji mojo is due to the X-Trans sensor. With its proprietary non-Bayer pattern design, the X-Trans sensor reproduces color in a unique way that's different from the way it's done in just about every other digital camera.

In my search to figure out what's really going on here, it occurred to me, (and was verified by a few of the Fuji reps and engineers), that the X-Trans sensor is actually very "film-like." It's much more so than most other sensors, and this is no accident. 

In designing the X-Trans sensor, the Fuji engineers looked back as much as they looked forward. Trying to preserve the heritage and legacy of traditional photography, they designed the "random" array on the X-Tran sensor so that it resembles the randomness of film.

As we know, film was essentially silver halide glitter that was poured into a bowl of jelly and smeared onto a plastic base. There was nothing "regular" about the way grain looked in film, and although the X-Trans sensor isn't totally random, it does closely match the look of actual film grain, especially when it comes to the distribution of the green sensitive pixels. Compare that with an actually cross section of Autochrome Lumiere film from the early 1900s. It's amazing how close the pattern looks to the X-Trans sensor pattern.

Also, compare the two image below, one is a scan from a Velvia slide, and the other is JPEG file from the X-T2.

You can see an expanded version of this topic on my blog, along with more image examples. I've even got a side by side comparison of the grain in ACROS next to the old T-MAX 3200 film.

I'm fascinated by this idea, let me know your thoughts!

 

TAURUS-07253A.jpg

X-Trans-Sensor_zps9cfjlzu2.jpg

Weaver_Alticolor_500x_scale.jpg

Below: An enlargement of the grain on an original Fujifilm Velvia slide film image. 

LGPK-105.jpg

Below: An enlargement of an X-T2 JPEG file.

AK-AERIAL-CHU-01635.jpg

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scharfsj

I agree, Dan! I think this is the "magic" that people refer to as to why Fuji files look wonderful, but in a way that is hard to put your finger on...

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artuk

The sensor makes little difference to final colour in my opinion and understanding.

every RGB full colour pixel in your jpeg must be recovered from groups of single colour pixels on the sensor. The X Trans layout simply requires different and more complicated mathematics to do so due to the relative scarcity of the red and blue pixels and the greater number of green. This actually created issues with image files containing colour smearing on edges of contrast where the demosaicing makes colour bleed form one area to another due to the need to recover colour data from a larger physical group of pixels than a Bayer design. Its also be shown to cause demosaicing artefacts that look like watercolour on fine org aic detail again due to the maths required and the need to compute larger groups of single.colour pixels together to get a single RGB value. This need to sample.larger numbers of nor widely spread single colour pixels also accounts for the "low noise" seen in RAF files as they are effectively performing noise smoothing (reduction) from the need to sample a larger set of values to produce 1 result. This tends to give the files a somewhat smooth look I my experience, which I think people equate to "filmic" (even though film wasn't smooth at all and actually very grainy up close!)

the biggest difference with Fuji colour rendition is that the results are not very accurate - colour analysis of jpeg output clearly shows that some colours are quite heavily skewed from normal typically to warmer values - this is most evident in the yellows and to an extend the orange and red colours too. I believe this is one of the main reasons for peoples view of the "look" of Fuji files.

the other factor at play that we cannot judge is the colour filter array used on the front of the Sony sensor - it is this that gives the pseudo random colour pixel layout but also determines the colour response of the R G and B channels depending on the exact colour of the colour filters used, and how the resultant data values and then interpreted to recover that colour data. For example,,some sensor stacks may give a much greater or lower response to a channel (e.g. Red) resulting in a uch larger or smaller red value - this then has to be interpreted the correct way in software to get the "correct" colour response back in a final RGB pixel.

Where you put each single colour pixel doesn't affect its response, but does convolute the maths needed to get back to the "correct" value. Some papers suggest Bayer layout sensors are the most mathematically accurate and effecient way to do this.

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veejaycee

I always shoot raw and process to my own liking. That may simply be to my own liking or to my memory of what I saw. Thus, I regard the colours and look of the resulting files as mine since they are a collaboration of Fuji, LR, PS, sometimes Nik and of myself. I'm not really sure if there is any noticeable difference between my finished Fuji files and my older Nikon files in respect of colour. Having said that, I preferred landscape colours from my old Nikon D200 CCD sensor over those from D300 CMOS. The D700 CMOS recovered some ground but maybe that was due to a difference in light gathering qualities of the larger sensor.

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roryp

I suspect the biggest reason for that different Fuji look is thanks to all those grouped green pixels. You get more luminance data and less colour noise which results in nicer rendering in many cases. There are some issues with certain scene types with lots of fine detail, mostly with Adobe's demosaicing algorithm, but even these usually vanish once you stop viewing your images at low DPI. One of the best things you can do for your Fuji files is to view them on a high DPI/retina monitor or as a quality print. People viewing Fuji files at equivalent to about 50 dpi (200% zoom on a typical monitor) and complaining about artefacts are missing the wood for the trees. 

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artuk
46 minutes ago, roryp said:

I suspect the biggest reason for that different Fuji look is thanks to all those grouped green pixels. You get more luminance data and less colour noise which results in nicer rendering in many cases. There are some issues with certain scene types with lots of fine detail, mostly with Adobe's demosaicing algorithm, but even these usually vanish once you stop viewing your images at low DPI. One of the best things you can do for your Fuji files is to view them on a high DPI/retina monitor or as a quality print. People viewing Fuji files at equivalent to about 50 dpi (200% zoom on a typical monitor) and complaining about artefacts are missing the wood for the trees. 

You are right that because there are more green pixels, but the colour pixels are much more sparse, you have to average a larger number of pixels in a group to recover a full RGB single pixel.  Bayer averages groups of 4 - 2 green, 1 red, 1 blue.  X Trans requires bigger groups to get the red and blue channels, so averaging a larger number reduces noise because you are sampling a larger set - it's why the raw files look cleaner because to demosaic them to full colour images by default includes some noise smoothing (noise reduction). The watercolour and artefacting is certainly there in some raw converters, including the in camera jpegs, but I agree at low magnification it doesn't show.  If you want to make larger prints, it could, since depending on the raw converter you use, the effect can be greater.  The green pixels by themselves don't affect the colour rendition - they just mean the files are smoothed as the demosaicing needs bigger groups of pixels to sample.

2 hours ago, veejaycee said:

I always shoot raw and process to my own liking. That may simply be to my own liking or to my memory of what I saw. Thus, I regard the colours and look of the resulting files as mine since they are a collaboration of Fuji, LR, PS, sometimes Nik and of myself. I'm not really sure if there is any noticeable difference between my finished Fuji files and my older Nikon files in respect of colour. Having said that, I preferred landscape colours from my old Nikon D200 CCD sensor over those from D300 CMOS. The D700 CMOS recovered some ground but maybe that was due to a difference in light gathering qualities of the larger sensor.

I do suspect that if one took raw files from an XA1 (Bayer) and an XM1 (X Trans) of the same scene, they would look so similar as to be the same - I don't think it's the sensor that gives the look, but the jpeg engine in camera.  As you say, when processing raw files, the colours look highly similar to every other camera.  It's only the in camera jpegs that have that specific "Fuji look".

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