Best downsize to reduce noise?

[Thomas Krüger]

Sizimg is a command line program for resizing an image with anti-aliasing, works great:
http://www.realitypixels.com/products/sizimg.html

[Fine_Art]

Images can be selected that aids generalized conclusions, and ones can be selected that does not aid conclusions. Comparing two images on my display of different sizes surely looks visibly different, but so does an image of a horse compared to an image of a cat...

My point being that you should resize image#2 so that it matches image#1. Then one can form sensible conclusions about which is "better". I could do this for myself, but my scaling might not be the same as yours, and then it would be difficult to exchange opinions.

-h

You seem to have forgotten what the OP was about. Can downscaling a noisy image improve the perceived quality? How much would be optimum? Its not "is your converter better than mine?" The comparison is downscaled vs original. My reply was use noise software before downscaling. The best %age I dont know. I think it depends on your noise removal software which is mostly a black box with sliders.

An exact measure would be to use a wavlet based noise reduction from the noise sampled in the picture. Based on that you would know what frequencies are removed the most so you would know what downscaling to use to present the detail that is left.

It sounds like you want a software comparison instead. That should be a different thread.

[eronald]

You seem to have forgotten what the OP was about. Can downscaling a noisy image improve the perceived quality?

That wasn't quite the question. The question was, IF I KNOW that I will be downscaling a RAW very substantially, is there a better way to process it, than going thru a standard Raw converter, then thru noise reduction and then through "standard" downscaling ?

Edmund

[BJL]

I am interested in the case where I simply don't need 24MP; Assume ... I am going into a BADLY LIT locale with an absolute NECESSITY to print a single magazine page or get a good web shot; that I need every bit of shutter speed and DOF I can squeeze out of the body and so I'm stuck with 6400 ISO. Now what is the best workflow to postprocess the 14 bit 6400 ISO Raw image into a colorful, sharp, small, destination file?

If small file size and low visible noise in the final smallish displayed image are the goals, then even though you do not _need_ 24MP, might the best solution be a combination of NR processing and, for file size, compressing the final JPEG? My sense is that both NR processing and JPEG compression algorithms can be far smarter than the "brute force" approach of downsizing, by choosing what information to discard and what to keep, likely giving more "IQ per MB" in the final file.

[hjulenissen]

If small file size and low visible noise in the final smallish displayed image are the goals, then even though you do not _need_ 24MP, might the best solution be a combination of NR processing and, for file size, compressing the final JPEG? My sense is that both NR processing and JPEG compression algorithms can be far smarter than the "brute force" approach of downsizing, by choosing what information to discard and what to keep, likely giving more "IQ per MB" in the final file.

I dont think that either JPEG compression or downscaling is the route to go for noise reduction.

1. Decide what output size/pixel-grid you are going to use
2. Scale, sharpen and NR into that grid in whatever order makes your tools produce visually pleasing results with minimal effort.

-h

[BJL]

I dont think that either JPEG compression or downscaling is the route to go for noise reduction.

Agreed, and apologies for my poorly worded subject line. I proposed JPEG compression only if file size reduction is needed, after NR processing. My understanding is that this is safer against moire and such than just downsampling, and keep the option open of zooming in on the details. And just printing the high MP file at high PPI is already useful for reducing visible noise.

[eronald]

what about jpeg2000

Edmund

Agreed, and apologies for my poorly worded subject line. I proposed JPEG compression only if file size reduction is needed, after NR processing. My understanding is that this is safer against moire and such than just downsampling, and keep the option open of zooming in on the details. And just printing the high MP file at high PPI is already useful for reducing visible noise.

[BJL]

what about jpeg2000

Indeed, why do we not see a lot more of JPEG2000, which seems unequivocally superior to the older JPEG, and is used quite a bit for archival image storage, using its loss-less compression mode? Maybe a thread on "going beyond JPEG" would be interesting. JPEG2000 does seem to offer full respecting of the bit-depth of the source data, and a graceful trade-off of IQ vs file size by discarding the higher frequenc parts of its wavelet encoded image.

But then again, I have read several comparisons arguing that Both PNG and the intra-frame compression mode of H.264 mathouts out-perform JPEG2000, and since H.264 intra-frame is used in some higher level video cameras, there is a tantalizing convergence for a video-plus-stills workflow.

[Fine_Art]

Indeed, why do we not see a lot more of JPEG2000, which seems unequivocally superior to the older JPEG, and is used quite a bit for archival image storage, using its loss-less compression mode? Maybe a thread on "going beyond JPEG" would be interesting. JPEG2000 does seem to offer full respecting of the bit-depth of the source data, and a graceful trade-off of IQ vs file size by discarding the higher frequenc parts of its wavelet encoded image.

But then again, I have read several comparisons arguing that Both PNG and the intra-frame compression mode of H.264 mathouts out-perform JPEG2000, and since H.264 intra-frame is used in some higher level video cameras, there is a tantalizing convergence for a video-plus-stills workflow.

Agree. H.264 should be the new standard for replacing jpg as most cameras that do video should have the standard in hardware. TVs are now going 4x 1920x1080p resolution. I can't wait to see my pictures in a 7680x4320 frame on the wall.

[hjulenissen]

TVs are now going 4x 1920x1080p resolution. I can't wait to see my pictures in a 7680x4320 frame on the wall.

4k is 4x the pixels of 1080p, or about 4000x2000 pixels. And one 80" monster was revealed at CES a few days ago at an unknown prize.

No content is available or suggested, the benefit is supposed to be upscaling 1080p.

With any luck, we will end up with tvs that do 4k, 120fps internally but with a HDMI input (and content) that is limited to 1080p24 and 1080p60.

-h

[hjulenissen]

Indeed, why do we not see a lot more of JPEG2000,

Used as a jpeg-replacement it seems to offer too little at too high a prize.

Say that you have an existing jpeg-based digital camera. You want less compression artifacts.

Option #1. Implement/purchase software/hardware that does jpeg2k encoding (using wavelets and very different tech from all other image/video coding). Deal with patent/ip issues. Deal with customers that are unable to read their files on the PC/mac/tv with usb image reader/...

Option #2. Increase the jpeg file-size by 30% and ask the user to buy a bigger memory card.

Which sounds like the easier sell? Add to this that the most demanding customers are probably using raw anyways.

-h

[ErikKaffehr]

Hi,

36 MP DSLR shots would be quite nice on 8K, don't you think? I'm using projector by the way so I can project any size ;-)

Best regards
Erik

4k is 4x the pixels of 1080p, or about 4000x2000 pixels. And one 80" monster was revealed at CES a few days ago at an unknown prize.

No content is available or suggested, the benefit is supposed to be upscaling 1080p.

With any luck, we will end up with tvs that do 4k, 120fps internally but with a HDMI input (and content) that is limited to 1080p24 and 1080p60.

-h

[eronald]

Used as a jpeg-replacement it seems to offer too little at too high a prize.

Say that you have an existing jpeg-based digital camera. You want less compression artifacts.

Option #1. Implement/purchase software/hardware that does jpeg2k encoding (using wavelets and very different tech from all other image/video coding). Deal with patent/ip issues. Deal with customers that are unable to read their files on the PC/mac/tv with usb image reader/...

Option #2. Increase the jpeg file-size by 30% and ask the user to buy a bigger memory card.

Which sounds like the easier sell? Add to this that the most demanding customers are probably using raw anyways.

-h

Doesn't explain why it is not being used as a software save option. Eg. as a compression integrated in Tiff.

Also, maybe Jpeg2000 or fractal compression does what I want, naturally.

Edmund

[Fine_Art]

4k is 4x the pixels of 1080p, or about 4000x2000 pixels. And one 80" monster was revealed at CES a few days ago at an unknown prize.

No content is available or suggested, the benefit is supposed to be upscaling 1080p.

With any luck, we will end up with tvs that do 4k, 120fps internally but with a HDMI input (and content) that is limited to 1080p24 and 1080p60.

-h

There is 8k along with 4k

UHDTV's main tentative specifications:[3]
Number of pixels: 7,680 × 4,320 (33.2 megapixels)
Aspect ratio: 16:9
Viewing distance: 0.75 H
Viewing angle: 100°
Colorimetry: under discussion
Frame rate: 120 FPS progressive scan
Bit depth: 12-bit per channel
Audio system: 22.2 surround sound
Sampling rate: 48 kHz, 96 kHz


There is also already IMAX movies which are about the same resolution. More IMAX material is needed.
Maybe this is why Sony, as an electronics company keeps pushing more pixels!

Added:


see also
http://www.ultrahdtv.net/sharp-ultrahdtv-prototype/

[Fine_Art]

Hi,

36 MP DSLR shots would be quite nice on 8K, don't you think?

Best regards
Erik

Exactly.

[hjulenissen]

There is 8k along with 4k

Sure, there might even be 16k, 32k or some other 2^N k spec down the line. Your post could be read like this was a technology that was available now, or one that for certain would be available at sensible prices reasonably soon.

My post was a claim that it is not so.

As long as the digital cinema spec only does 2k@48fps and 4k@24fps (incidentally using jpeg2000), I don't see home cinema going any further soon (they would not dare having better specs at home than in theatres). Still-image is a different segment, and I could see them driving higher resolutions.

http://en.wikipedia.org/wiki/Digital_Cinema_Initiatives#Image_and_audio_capability_overview
"2048x1080 (2K) at 24 frame/s or 48 frame/s, or 4096x2160 (4K) at 24 frame/s
In 2K, for Scope (2.39:1) presentation 2048x858 pixels of the imager is used
In 4K, for Scope (2.39:1) presentation 4096x1716 pixels of the imager is used
Stereoscopic 3D Image:
2048x1080 (2K) at 48 frame/s - 24 frame/s per eye (4096x2160 4K not supported)
"
-h

[hjulenissen]

Doesn't explain why it is not being used as a software save option. Eg. as a compression integrated in Tiff.

If most customers dont want it, researchers think that it does not bring enough of a benefit, marketers don't know how to advertise it and economers worry about licensing costs, it probably won't be introduced.

I think that the combination of jpeg for small file-size delivery and lossless formats for archiving works very well for me and many others.

Also, maybe Jpeg2000 or fractal compression does what I want, naturally.

What do you mean?

-h

[hjulenissen]

36 MP DSLR shots would be quite nice on 8K, don't you think? I'm using projector by the way so I can project any size ;-)

Yes. I think it is the only feasible way we may someday be able to view the full DR of new sensors/HDR without excessive tonemapping. Probably direct-lit displays and not projectors, though.

-h

[BJL]

Used as a jpeg-replacement it seems to offer too little at too high a prize.
...
Add to this that the most demanding customers are probably using raw anyways.

That sounds right: JPEG and TIFF are ubiquitous and between them meet most people's needs ... and those what want more go for raw.

And there is no commercial motive to drive JPEG2000 adoption, whereas several other recent alternatives have big corporations behind them while being "open" in the limited sense of the format definitions being published and usable free of license fees.

1. Microsoft has had its "HD Photo" format adopted as the JPEG-XR standard, with a promise of fee-free patent licensing, and is adding support for that to its software. JPEG-XR does not use wavelets like JPEG2000, but has the option of a two layer system of 4x4 and 16x16 blocks, which achieves some for the wavelet virtues without the memory bandwidth needs of the inherently global wavelet transform.

2. Google is pushing yet another alternative, WebP, but maybe just for web-page display.

3. As someone said, hardware support for H.264 is becoming common, and one trend these days is that video drives technological changes more than still photography, so maybe the attraction of full still-quality frame grabs from an H.264-intra video will favor that format.

[ondebanks]

Bill, here is may question. If I have two 16x20 prints viewed at 20 inches and from the same image, but one was from the original file and one was down sampled, would I see a difference in noise? Would the visual system do the basic averaging work of down sampling?

Yes, you would see a reduction in noise - especially if the down sampling used something like the median of values within each block of pixels, implicitly rejecting outlying values, which in most cases means rejecting noise.

But more obviously than that, you would see the reduction in resolution.

And if you are not standing close enough (or the photo is not enlarged enough) to see the reduction in resolution, then you are not able to perceive the full resolution of the original either...nor its higher noise at the pixel level - I guess this is what you mean by "would the visual system do the basic averaging work of down sampling".

It's always possible to trade pixel resolution for noise, and vice-versa (the D3X designers knew they were doing this, in comparison to the D3).

Ray