Jump to content

Color detail issues in Fujifilm video files


Attila Bakos
 Share

Recommended Posts

EOSHD Pro Color 5 for Sony cameras EOSHD Z LOG for Nikon CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs
1 hour ago, Attila Bakos said:

I have access to an X-T3, EOS R, and 5D3. The GFX samples I found online. Did you mean to test with the X-T3?

Yeah, and compare it to the other two.  If it has huge amount of noise because of the X-Trans sensor then we'll know, and if it doesn't, we'll know the chroma processing isn't for NR.

Link to comment
Share on other sites

1 hour ago, kye said:

Yeah, and compare it to the other two.  If it has huge amount of noise because of the X-Trans sensor then we'll know, and if it doesn't, we'll know the chroma processing isn't for NR.

Unfortunately I won't have the time to test this anytime soon, and I'm not sure it's worth it. The Petapixel artice is absolutely correct about the interpolation issues of the X-Trans pattern, technically there is more guesswork there, and the camera won't have the processing power for a sophisticated demosaicing algo. It's pretty slow even on PC. So I'm sure that the in-camera demosaicing leaves some color artifacts that Fujifilm chose to hide with chroma NR, but they might have gone overkill with that. And I'm surprised that I don't see an improvement on the GFX bodies.

Link to comment
Share on other sites

On 2/20/2022 at 6:41 AM, Attila Bakos said:

If it's the X-Trans CFA, what's the explanation for the GFX results I posted earlier? 

 

On 2/19/2022 at 8:57 PM, Django said:

Fuji apply heavy chroma NR in their Jpeg/h264/h265 engine for their immune-to-moiré claims of the X-Trans CFA.

I assume they do the same in the GFX100 as that model does not have an optical low-pass filter despite being a Bayer sensor (Fuji claim its megapixel count is so high it can resolve complex textures with little to no moiré effects).

A quick search on GFX forums confirms this:

Same with my GFX 50S.

The OOC jpgs have heavy chroma NR applied (with in camera NR -4).

Developed raw, with NR off or low, moire false-colour artefacts become apparent (colours between dead white stalks in field below), though small coloured objects are retained - such as red berries on distant trees, even the subtle colour shifts in the autumn leaves is lost. The chroma NR removal of fine coloured information in the OOC jpg is great loss IMO.

The bayer CFA of the GFX is v.prone to moire and false colours on hard edges, but not x-trans - with those sensors OOC chroma NR need not be so high.

Fuji X jpg engine chroma noise reduction setting very high

Link to comment
Share on other sites

1 hour ago, Attila Bakos said:

Great... I'd rather have an OLPF and slightly less overall resolution than slightly more luma and noticeably less chroma. Or at least they could allow us to modify/switch off the chroma NR.

You're not alone with that thought, which is why many including myself left the system. The option to turn off chroma NR should definitely be there, especially since unlike in RAW stills there is no getting around it in video.. 

Like I've been repeating, this an infamous issue in the Fuji community. It's kind of a taboo subject though. Whenever it gets brought up,  people usually dismiss it by saying shoot RAW. I still think its quite jarring as the jpg film simulations are a huge part of the Fuji-X philosophy. 

Again, for videographers there is simply no workaround this issue, hence this topic should really be brought to Fuji's attention imo.

 

Link to comment
Share on other sites

On 2/17/2022 at 12:28 PM, Attila Bakos said:

There must be some clever algorithm behind this as it seems to have proper 1080p resolution around well defined edges, but everywhere else it's clearly less than that.

It appears that Fuji is essentially using wavelet/frequency-separation in the chroma channels to isolate and blur certain areas.

I tried that scenario on your "5D3 Raw" chroma channel image (captured from your Resolve viewer with MPV), using the Darktable Contrast Equalizer module:

mpv-shot0004.thumb.jpg.bd982fbd19cff4ad523485addabfd8a7.jpg

I didn't get it to look exactly the same as the X-T3 chroma channel image, but the "blotchiness" achieved is fairly similar.

Here is the curve used in the Contrast Equalizer module:

contrast_equalizer_curve.jpg.7abb7840fded327a3db4ecc680ca7e20.jpg

The scale from left to right delineates coarse patterns to fine patterns in the image.  The mostly flat line going through the center is the sharpness curve, and the "S-shaped" line is the smoothing curve.

Many use the Contrast Equalizer for denoising and sharpening, but in such applications, the smoothing curve always lies below the sharpening curve.  Nobody ever inverts the two curves as shown on the right side of the graph.

I also used the Soften module with a parametric mask to add extra blur to the brighter areas, because the Contrast Equalizer did not provide enough blur.

The excessive chroma blurring from the X-T3 way too much for demosaicing, and it's extreme overkill for noise reduction.  There also seems to a bit of coarse pixelation revealed when you zoom-in in your video, so perhaps Fuji is additionally doing a pseudo chroma subsampling.

Whatever Fuji is doing (and for whatever reason), the process is effectively reducing the color resolution, which results in a perceptible loss of color depth.

 

On 2/18/2022 at 2:13 AM, kye said:

It's nothing to do with resolution @tupp, otherwise the RAW files would be impacted too, it's processing.

The X-T3 is excessively lowering the effective chroma resolution with blurring, which dramatically reduces the color depth.

The raw files don't have that problem, because their resolution is not being reduced.

The "processing" is likely something similar to what I have shown above, and it essentially is reducing the color resolution, hence the lower color depth.  Remember, with digital imaging:

COLOR DEPTH = RESOLUTION x BIT DEPTH

By the way, when are you going to take back that lie you told about me?

Link to comment
Share on other sites

6 hours ago, tupp said:

The X-T3 is excessively lowering the effective chroma resolution with blurring, which dramatically reduces the color depth.

The raw files don't have that problem, because their resolution is not being reduced.

The "processing" is likely something similar to what I have shown above, and it essentially is reducing the color resolution, hence the lower color depth.  Remember, with digital imaging:

COLOR DEPTH = RESOLUTION x BIT DEPTH

Ok, I think with your explanation this is starting to make some sense.  When you outlined it before you didn't provide nearly enough information.

6 hours ago, tupp said:

By the way, when are you going to take back that lie you told about me?

Maybe it was a mistake to unblock your profile....  🙄🙄🙄

Link to comment
Share on other sites

  • Administrators

What impact if any does Color Chrome Effect have on this in the Fuji menus?

Is it possible Fuji's processing by default blurs the chroma channel so that dialling in certain film simulation settings brings it back and changes the look?

It must be on purpose they have done this.

Link to comment
Share on other sites

Here is another free GUI app to view Y Cb Cr:

https://www.gimp.org/

Use the drop down menu COLORS / COMPONENT / EXTRACT COMPONENT,
and then there is another drop down menu to select the type of component to view,
including Y, Cb, Cr.

Alternately there is also COLORS / COMPONENT / DECOMPOSE.

Must admit I am finding it difficult to see any loss of red details or color blurring comparing

my X-T3 to my Canon T2i.  But so far I've shot indoor subjects only.

No wonder it took 4 years to notice!

 

Link to comment
Share on other sites

On 2/23/2022 at 3:40 PM, Andrew Reid said:

What impact if any does Color Chrome Effect have on this in the Fuji menus?

Is it possible Fuji's processing by default blurs the chroma channel so that dialling in certain film simulation settings brings it back and changes the look?

It must be on purpose they have done this.

Isn't Color Chrome for images only? I don't see how I could enable that for video on my X-T3.
My feeling is that the processing is there to hide something, not to enable something.

Link to comment
Share on other sites

On 2/21/2022 at 10:17 AM, Django said:

 

A quick search on GFX forums confirms this:

Same with my GFX 50S.

The OOC jpgs have heavy chroma NR applied (with in camera NR -4).

Developed raw, with NR off or low, moire false-colour artefacts become apparent (colours between dead white stalks in field below), though small coloured objects are retained - such as red berries on distant trees, even the subtle colour shifts in the autumn leaves is lost. The chroma NR removal of fine coloured information in the OOC jpg is great loss IMO.

The bayer CFA of the GFX is v.prone to moire and false colours on hard edges, but not x-trans - with those sensors OOC chroma NR need not be so high.

Fuji X jpg engine chroma noise reduction setting very high

Since the GFX 50 and Hasselblad X1D share the same sensor.
Is the X1D affected by this as well?

Link to comment
Share on other sites

23 hours ago, Jay60p said:

Here is another free GUI app to view Y Cb Cr:

https://www.gimp.org/

GIMP is not only free -- it is also open source.

 

23 hours ago, Jay60p said:

Must admit I am finding it difficult to see any loss of red details or color blurring comparing

my X-T3 to my Canon T2i.  But so far I've shot indoor subjects only.

Are you testing raw stills, jpeg stills or video frames?

Link to comment
Share on other sites

On 2/27/2022 at 1:23 PM, tupp said:

GIMP is not only free -- it is also open source.

 

Are you testing raw stills, jpeg stills or video frames?

I shot jpegs at highest resolutions, at ISO 800. I pixel-peeped at 100% scale.

I did not use video frames, video from the T2i is only 1080p and rather soft.

I was able to use the same lenses on both cameras, Super-Takumars with M42 adapters.


But, this issue needs more tests with low contrast mixed colors,

I’ve think that’s where the small color details may get muted, mistakenly treated as noise.


So I’m not bothering to post my shots showing how well the chroma NR works

with medium to high contrast colors, I think that is already obvious to any Fuji user.

No, we need to complain to Fuji about this foliage issue.


Attila Bakos’ Cr component images show that Fuji needs to give us control over the amount of

chroma NR, same as luminance NR.

Landscape photography needs it, if nothing else.  

There should be an option of balancing color noise vs. color detail.  

A chroma NR setting of -4 to +4 would neatly solve this problem.

Or even “On/Off” would be better than nothing.

And we should not have to shoot RAW (if that comes in the X-H2) to get around this issue.

 

Link to comment
Share on other sites

  • 4 months later...

I just had a chance to take a look at some X-H2s originals shot in F-Log and F-Log2 in H.265, and it seems to me that the chroma smoothing is way less aggressive in this camera. It's still there, but it won't cause problems I think. This is just my first impression, not a deep analysis. And now you can completely get rid of the smoothing by shooting raw to an external recorder, I tested this with a ProRes RAW HQ clip. What I couldn't test is ProRes internal.

I also noticed that the H.265 files are now tagged with the BT.709 matrix coefficients instead of the BT.601. This will definitely solve some interpretation issues. One small downside is that the files are no longer full range (at least the F-Log and F-Log2 originals I received), they only use the limited range, so we lost some precision here.
 

Link to comment
Share on other sites

Ignore my comment about the X-H2s having better chroma channels. Just received the same clip shot on an X-T3 from the guy who provided the X-H2s clips, and the chroma channels are good on the X-T3 too, at least in this shot. More extensive testing is needed. And I might just as well upgrade my X-T3 to the latest firmware and re-test it, who knows... 🙂

Link to comment
Share on other sites

Okay, for those who find this kind of stuff interesting, here is a comparison of Cr channels (with added contrast for easy visualisation) from the C70, X-T3, and X-H2s:
https://www.dropbox.com/s/pbfjdx4c2zxhhzq/chroma_compare.mp4?dl=1

C70 is C-Log3, 100Mbps
X-T3 is F-Log, 400Mbps
X-H2s is F-Log, 360Mbps

There is definitely an improvement over the X-T3.
(I only received this files from someone, so I can't do other comparisons.)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • EOSHD Pro Color 5 for All Sony cameras
    EOSHD C-LOG and Film Profiles for All Canon DSLRs
    EOSHD Dynamic Range Enhancer for H.264/H.265
×
×
  • Create New...