Chroma noise & color grading

[Till Krueger]

ooops...my bad...Helen was reporting up to 5 hours for 1 *minute* of finished video...so about 10 secs per frame.

David,

do you think that you can tweak your algo to the point of getting results as close to flawlesness as Helen's? not to say that what you posted looked very, very good as well...especially considering the speed of processing.

[Helen Mets]

To clear up the time issue: I always upsample the images to 2k (sometimes 4k) before applying any filters.

Till Krueger is nonetheless on the right track. I usually repeat the
color range/color balance 3-10 times, depending on the amount of noise (and different shades of color). Once I've reached more or less decent results, I blur the color channels with the 'median' filter. This tends to introduce some color bleeding in certain areas, so I use 'find edges' command to create a selection of the unblurred image to be placed on top (edges only). I use several passes here as well, to create a smooth decrease of median values towards the edges.

I hope this isn't too confusing...

Peace,
Helen


PS. Although every action I create is scene dependant, I think it's quite possible to write a plug-in that achieves similar results. It would be cool if someone could do that.

[David Newman]

Tim,
I doubt it as mine is automatic, no human intervention. Greater filtering will take longer. For more natural images, with better tonal range, my current filter works very well, only that Matrix clip gave it some real work.

[Helen Mets]

Sorry David, didn't mean to put you down with my last remark about the plug-in, I was just thinking that your filter approached the noise reduction differently than what I have been doing.

[Till Krueger]

Helen,

i see where you're going with this...no, it's not too confusing (at least to me), but i can see where a lot of practice comes in here.

David,

yes, the Matrix footage has got to be one of the worst possible scenarios, and it must be true that more "natural" scenes could pose less of a challenge and exhibit - subjectively - cleaner results...i think that including that funtionality in your upcoming upgrade to Aspect HD would add the kind of value that could tip people like me over the edge between contemplating buying and going ahead with buying...

i am aware of the fact that even $1.2K are still a good buy in comparison to competing hardware solutions (which can run 10x the cost and more), but i have also been in the industry long enough to know how quickly a small upgrade to an already owned application (Premiere Pro, Vegas, etc.) can make a separate plugin obsolete...

but it's the kind of features that you have added, and are adding as we speak, such as real-time transitions, slow-motion, or the upcoming DNR etc., that make it tasty even to the "motion graphics and digital designers gone HD" such as me.

Helen's post has definitely started something, if you ask me...i am sooo reminded of the first couple of years of digital SLR photography and dealing with some of the artifacts of the otherwiese excellent results (i.e. the low light banding of the Nikon D1, or it's "magenta cast" problem)...there will at least be 2-3 years of opportunity ahead of us, for those that can automate the kind of tweaking that is necessary, such as what Helen is doing so very carefully, skillfully and effectively.

eventually the format/chips will mature...look at the excellent CMOS chip in the Canon 10D/300D now, that puts cleaner than the best of 35mm photography into the hands of the "consumer level" customers.

excuse my ranting, but i am excited about all of this.

thanks ya'll for this wonderful forum!!!

[Paul St. Denis]

I think I have been getting nice results using avisynth, and the plugins cnr2.dll and TemporalCleaner.dll
here is a before:
4 megs Windows Media 9
http://www.celt.sunysb.edu/paul/HD_s...karendirty.wmv

and after:
4 megs Windows Media 9
http://www.celt.sunysb.edu/paul/HD_s...karenclean.wmv

[David Newman]

Helen,

No offense taken. Yes, the technique I have applied is quite different. I orginally looked into this to see if I could improve chroma keys, without impacting luma at all. As I result my filter only manipulates the U and V components.

Tim,

Thanks for the nice comments on our features and pricing. We are too often thought of as the expensive solution, yet many forget that real-time HD is typically too expensive to even consider. CineForm is trying our best to make RT-HD affordable to all pro. and prosumer applications.

[Paul St. Denis]

Isn't anyone going to take up Graeme Nattress and his offer to build a FCP filter to specs?
Graeme I don't understand the cause of chroma noise enough to describe what we would need in a filter to remove it. But I would certainly appreciate anything you could build to improve the look of the HD footage produced by these cameras.

[Till Krueger]

yes, Graeme...

excuse the delayed reaction, but such a plugin for FCP would be *MOST* welcome.

personally, i am on the PC right now (as i am sure many others are in this JVC HD case), but i have been looking at FCP and DVD Studio Pro for future projects...so if you really feel up to the task, let us know what we can do to supply example footage, ideas, feedback, etc.

[Graeme Nattress]

Yes to all the above - drop me an email so you can arrange to send me some test footage, and keep on board for specs of what it is exactly I need to do...

Graeme

[Helen Mets]

Paul,

These are fine examples you posted, although I noticed certain loss of resolution on the 'clean' clip. It seems that the plugins you used affect the luma channel as well.

[Paul St. Denis]

Here are the same frames cleaned and otherwise.

http://www.celt.sunysb.edu/paul/HD_samples/2.tif

http://www.celt.sunysb.edu/paul/HD_samples/1.tif

I have said before that I don't think my eyes are that discerning, but I don't notice a heck of a loss of detail here. Look at the wisps of hair for comparison.

It is possible that the temporal smoother mucks with the luma channel, cnr2.dll is specifically a choma noise reducer and does not touch luma according to the author.

[Till Krueger]

Graeme,

i think the Matrix clip would be a great starting point as far as footage goes, because it is such an extreme example of noise...actually the noise in this clip is so extreme mostly because of the subject matter of the imagery...dark, even surfaces are the most noticable problem areas.

but the storefont clip with the Australian girl that has skin totally messed up by CN blotches would be a good example of low light portrait style shots...i don't think the whole clip was ever posted...the storefront footage would be a great example of a more "real life" scenario than the Matrix clip, though.

i have totally random shots from my first few days with the HD1, and if you could let me know what you need other than what is already there, i'd gladly pick a couple that meet the specs you would like to see...5 seconds should suffice, right?

the most productive methodology in my eyes, however, would be one where a color chart/resolution target is shot at different exposures...this way there would be a more reliable witness to actual color and resolution shifts...as i was playing with some of Helen's Photoshop ideas, i quickly found that what works well for one image, won't work so well for another one...color variations are just too big from scene to scene...

soooo, how does one find a solution that works for as much of the footage as possible? maybe David has already found one of the most effective ways of doing this for his Aspect HD platform...one second a frame is certainly very little in the light of what i have found other solutions to use up.

what else are you looking for as far as specs, etc.?

[Helen Mets]

At this point I would like to call everyone up to post crabs or short clips (2-3sec) of material that seems most problematic in regard to noise and saturation. Esp. kind of material that cannot be cleaned up with designated plugins/actions. I need the challenge.

The Matrix clip is a good example of bad noise, but it's very monochromatic. I would like to get my hands on similarly horrid material, but with more versatile palette.

Cheers,
Helen

[Paul Mogg]

I have a LOT of good examples that I'd like to send you, please let me know where I can send them to and how many and how long clips you would like.
For me it is the flat areas of mid-tone colors that are the big problem with chroma noise, such as the side of a one-colored building, plain blue skies, flat blue/green water. Also very saturated reds display chroma noise a lot.
Helen, would it be possible (or even a good idea) for you to share your Photoshop settings with Graeme so that he could use them as a guideline for building an FCP chroma-noise reduction filter?. Not knowing enough about how the FCP filters are built I don't know if this is a ridiculous idea, but I just thougt I'd suggest it.

Thank you for looking into this, I think it's wonderful to see the cooperation that is going on on this this website to find creative solutions to problems with this HDV format, it's so much better than when the camera was first released when all we got was negativity from so many people.

Paul