Possible sRAW for DSMC?

[Tom Lowe]

Hopefully I am not suggesting something that is already announced or in the works... :blush:

With native, full-sensor resolution in the neighborhood of 6K, it sure would be nice to have a half-scale sRAW option. I notice that on my 5D2 when I shoot full-sensor, 21MP RAW files and import them as footage into AE, my CPU gets destroyed. Like, I set the thing to render, then I can take a 2-day trip to Catalina while I'm waiting for it to finish. hmy:

But I did shoot quite a few scenes in sRAW, which is only roughly 1/2 res but maintains all the flexibility and power of RAW.

RAW = 5616 x 3744 (21.0 MP)
sRAW = 3861 x 2574 (10.0 MP)

The images created by sRAW are super clean, sharp and beautiful. Perfect for 2K finishes. This saves CF cards, and spares my CPU the humiliation of 5.5K!!

I notice on Epic FF35's specs it says:

6K 1-100fps
5K 1-125fps
4K 1-150fps

FF1080p 1-60fps

I assume the 5K and 4K are cropped? Is that FF1080p basically a scaled down RAW, or some type of processed RGB or something?

I don't have a clear understanding of how Canon's sRAW process works, but I can tell you one thing: it works beautifully.

Shot sRAW1....

 

[Graeme Nattress]

The "half high" direct demosaic of 4k to 2k probably gives you the benefits you'd need - speed and quality, but it doesn't stop you going back to the 4k RAW if needed.

Graeme

 

[Tom Lowe]

Graeme, do you understand how Canon is doing their sRAW?

I'm curious to know how it works.

 

[Graeme Nattress]

I know of a number of possible ways that they could be doing it. The major advantage for Canon is that you get a smaller RAW file to write in camera. That's not so much an issue with the speed we can write files.

Graeme

 

[Tom Lowe]

I tell you, though, it is nice to be able to select that sRAW in the field.

 

[Graeme Nattress]

The sraw is probably doing some kind of binning. That could lead to excessive aliasing. I'll have to investigate further...

 

[Tom Lowe]

Just tell Jim you need a 5D2 right away for your investigations. :wink:

 

[Graeme Nattress]

I think my 1D mk III does sraw too...

 

[Deanan]

IMHO, REDcode with a half res high decode is superior to sRAW in many ways. The downsampling that sRAW uses is not very elegant.

 

[Daniel Browning]

You already know how I feel about this from past threads, Tom, so don't feel like you have to respond, but I want to post the following anyway so that everyone else knows how much I am annoyed by Canon's sRAW mis-feature.

With native, full-sensor resolution in the neighborhood of 6K, it sure would be nice to have a half-scale sRAW option.

I think it would be nice, too, as a very last resort, after all the better compression methods are implemented and you still need smaller file sizes.

Asking RED for something like this is like asking Mario Andretti if he can also drive 5 MPH go carts, or asking Michael Phelps if he can also swim in the kiddy pool. RED can do it, sure, but they left the kiddy pool long ago.

Below I'll discuss why Canon's 21 MP RAW should be 3 MB instead of 26 MB, even at full resolution.

...21MP RAW files and import them as footage into AE my CPU gets destroyed.

There are several solutions to this, including, as Graeme mentioned, things like RED's half-high demosiac or faster full-res algorithms. Even in the worst case scenario, software could always convert the full res RAW down to sRAW after the fact. Adobe is definitely not a good example of providing flexibility in choosing demosiac algorithm.

Things like sRAW should solve in-camera challenges (card space, etc.), not Post challenges that have better solutions.

I don't have a clear understanding of how Canon's sRAW process works,

I don't either. My current theory for 5D2 sRAW1 is that two GB/RG groups (8 RAW pixels) are converted to two pixels that have unique G, but the same R/B.

But I did shoot quite a few scenes in sRAW, which is only roughly 1/2 res but maintains all the flexibility and power of RAW...it works beautifully.

What is the purpose of sRAW? To reduce file size.

How does it achieve this? By throwing away resolution.

Is that the best Canon could think of? The very first time they try to reduce file sizes and nothing else comes to mind except to immediately start dumping pixels?

It's like a plane with 21 passengers and a cargo hold full of garbage. When the plane is too heavy, Canon immediately resorts to throwing passengers out of the plane, while keeping all the garbage.

I'm glad RED didn't suffer that kind of tunnel vision, REDCODE sRAW would be 168 MB/s (1344 Mbps) and only 3K.

That's why sRAW is the laughing stock of file formats. In some cameras, like the 50D, half of the sRAW2 filesize is wasted on two embedded jpegs, and the rest only contains a quarter of the resolution.

First of all, there's a simple nonlinear bit-depth compression they could do, like Nikon. The difference is invisible to the human eye, but that alone saves a tremendous amount of disk space.

Next, they could make the embedded jpegs optional, at the cost of making reviews a little slower. (I don't use the embedded jpegs anyway since Canon also doesn't bother providing truly raw RGB histograms and I have to use UniWB).

After that they could compress bit-depth on a scale of exposure. You don't need 14 bits to record a scene at ISO 12800. Six or maybe 7 bits would be enough to encode the entire signal down to the noise floor. For every stop that exposure is decreased, the noise floor gets higher. The bit depth should be decreased to match the noise level. This compression wouldn't help or affect base ISO shots at all, but would make a huge difference for high ISO shots.

On the subject of bitdepth itself, the noise in the camera at base ISO isn't even clean enough to require 14 bits. 12 bits is more than enough to encode the entire range of signals as well as a half-stop of noise. This has been tested and the last two bits are truncated in post and it makes no difference.

Now that's four things that reduce filesize without *any* affect on the resulting image. Still has full resolution, RAW, etc. My calculations show that for a high ISO shot, file sizes would be 1/8th what they are now. That's 3 MB for the 5d2. I'd much rather have that then the half-resolution 15 MB files Canon has now.

But why stop there? There is an entire world of compression they could apply to the image with imperceptible affect on image quality. Cineform RAW and REDCODE show that technology exists to reduce file size in ways that are visually lossless to the eye. At the very least, the "lossy" effect will be much smaller than just dumping entire pixels. Unlike the methods I've already discussed, many of these methods, I'm sure, require some CPU power in the camera.

If the camera is too weak to do any sort of medium-to-advanced compression (and it probably is), then sRAW would be an acceptable compromise. But not until all the better ideas, the least of which are outlined above, which do not require any camera CPU power, are already implemented.

In the case of RED, it would be nice if they offered this type of lossy compression so that filesizes were reduced and recording time increased, but only after the camera CPU is taxed to the limit with the more efficient methods.

 

[Graeme Nattress]

View attachment 9390

Canon 1D MK III, 50mm F.14, locked off on tripod, shot both RAW and sRAW.

 

[Daniel Browning]

Canon 1D MK III, 50mm F.14, locked off on tripod, shot both RAW and sRAW.

Ewwww! Another and even more important reason to hate sRAW: aliasing artifacts. Doesn't look like Canon even *tried* to filter out details from the new Nyquist before they resampled.

Maybe Canon should rename sRAW to 'Sigma Foveon mode': less resolution and more artifacts. (They still need to do worse in the low light performance before they'll match Sigma in that regard.)

 

[Tom Lowe]

Graeme, in all fairness, test the 5D2's sRAW.

IMHO, REDcode with a half res high decode is superior to sRAW in many ways. The downsampling that sRAW uses is not very elegant.

I don't know what to say. It seems extremely elegant so far IMHO. These images I am seeing at 2K finish are beautiful. Plus the fact that you are only recording 1/2 the CF card space. That is useful.

A lot of pixel peepers at DPR and some astro guys are saying that sRAW on the 5D2 gives you the beauty of full frame plus the benefits of a downsample (in terms of noise reduction).

I'm just reporting what I have heard.

 

[Chris Kenny]

Downscaling is never as effective in terms of preserving significant image data while reducing file size as is a modern image compression algorithm. As an extreme example of this, consider the fact that REDCODE 28 has about the same data rate as SD uncompressed video. Clearly we're much better off with REDCODE than we would be if the Red One downscaled everything to SD before recording it.

Downscaling does have the benefit of requiring much less processing power, which might matter in some embedded applications, but clearly isn't an issue with Red's gear; high-quality compressed raw recording is practically the centerpiece of Red's technology program.

 

[conrad gaunt]

My understanding is, the new Red cameras will downsample FF to 1080p, and save it as a wavelet compressed RGB file, not a RAW file (like cineform RGB perhaps).

This will give you a measure of oversample, which brings a little noise reduction, anti-aliasing and what i call "density", that sRAW and CFAs don't (and it'll take less space than a Canon sRAW file).

This will be useful for when 4k is overkill on smaller productions, but downsampling a Full quality debayered 4k frame, then downsampling with a high quality software downsampler is my prefered route when time allows.

What would be amazing is if Reds RGB format could go beyond just being an "injest only" format.

Better still would be a lossless wavelet version of redcode, that could be exported to (like cineform RGB, but bigger, slower, lossless, so no toes trodden on!)

 

[Tom Lowe]

Here is what the illustrious Ken Rockwell has to say about sRAW...

Try shooting your 5D Mark II at it's M (11MP) or S (5MP) settings. If you look at your images at 100%, you'll see that the lower resolution shots are sharper!

Why? Because they use less, or no, Bayer interpolation. No digital camera really resolves its rated resolution; they cheat and interpolate up, so at 100% at its rated resolution, no digital camera image is as sharp as a true scan from film.

At the 5MP setting, you have 100% R, G and B pixels, exactly as if you were using a Sigma Foveon sensor. If Sigma was selling this, they'd sell the 5MP (S) setting as if it were 15MP (also a lie).

http://www.kenrockwell.com/canon/5d-mk-ii.htm

 

[Graeme Nattress]

I don't think it wise to ever base a photographic / imaging argument around anything Rockwell has to say. The images I took speak for themselves in what is happening.

Graeme

 

[Jannard]

Looks like Canon IS having some sRAW issues with the 5D II...

http://www.dpreview.com/news/0812/08121902canon5ddots.asp

Jim

 

[Tom Lowe]

I don't think it wise to ever base a photographic / imaging argument around anything Rockwell has to say. The images I took speak for themselves in what is happening.

Graeme

Lol I'm not vouching for Rockwell, I just posted what he had to say.

So Graeme what do you think they are doing exactly to accomplish this sRAW?

 

[I Bloom]

Now I'm trying to figure out what the Red FF1080p mode is.
I'm hoping it's fully debayered, scaled to 1080p RGB, wavelet compressed. But thinking that's impossible or maybe not necessary.

IBloom