Why 4k

[Gavin Greenwalt]

Well, isn't DOF dependent of the Circle of Confusion used? A 4Kprojection has a different CoC of a 2K projection. So Wouldn't it have some consequences on DOF?

(For instance, 35mm motion picture has different DOF when it's projected in a theather or when it goes to SD television. Technically, the DOF is the same, but since there aredifferent tolerances for the different viewing methods, DOF does change...)

The CoC will change, but it'll be a linear shift so it won't effect the DoF just the 'focus'. It's like applying a Gaussian blur to a 4k image. The DOF hasn't changed, since everything was affected evenly.

 

[Jeff Kilgroe]

I once had to roto, in 2k, a man swinging his body around wildly, of course he had long hair. It wasn't meant to be an fx shot, but the production decided to digitally change the background.

<warning, stupid question> ..Uh, why couldn't the shot just be re-done?

I know, I know... it doesn't always work that way, especially when the decision is made weeks or months down the road. I feel your pain though.

 

[Jeff Kilgroe]

I don't see 4k as being 4 times the work though,

4k rotoing isn't going to be slower. Roto work is a human tracing an edge with vector tools. Image resolution doesn't make this process take longer, and the cleaner the edges to see, the better, I'd think, not worse.

I'm with Graeme on this one. And if the milk girls are anything to judge by, my roto and keying work with RED will become a much better experience. It's all about the crispness and clarity of the imagery you're working with and I would gladly do comp work with 2K or 4K RAW from a good camera system with great optics any day over 1080i DVCPROHD or <oh, lord!> HDV.

CG work is going to take longer to render. That's true, but it's not the end of the world as render power is growing much faster than image raster size

Yep. I've got a decent render farm -- puny by Hollywood standards, but I can render faster than I (and my limited help) can work. I often wonder how many "pro" 3D guys out there get by without a decent render farm, even single-man operations. With a good farm, I can take on more jobs at lower cost, faster turn-around times, I can have rendered sequences often while working direct with the client on changes, etc.. I've just made it a habit from the beginning to allways include the cost of a new render node into a job wherever I can.

 

[_BK]

I don't see 4k as being 4 times the work though,
4k rotoing isn't going to be slower. Roto work is a human tracing an edge with vector tools. Image resolution doesn't make this process take longer, and the cleaner the edges to see, the better, I'd think, not worse.

Interesting thread here.... I dont think rotoing 4k will be 4x as slow, however it will be quite a bit slower than 2k or HD. When doing roto you need to push an enormous amount of data through a network as the roto artist is constantly scrubbing frames and caching frames into memory. At 4k the artist will have to still push 4x the data though the Roto package and cache. Sure, you can do most in proxy res, but final roto would still have to be done at the full res.

Im scared to think about doing closeup CGI at 4k, the amount of work and rendering power/memory needed to do that is unreal. But, the availability of a 4k plate even if you are outputting at 2k or HD is great for things like tracking and matte paintings.

 

[Zak Forsman]

this freedom to reframe in post is very intriguing. i do alot of improvisation so the ability to punch-in and keep the continuity of the performance is... wow. i've got to think about this. suppose i'd have to settle on mastering out to 2K. at 4K the punch-ins and reframing would be pretty obvious, im sure.

 

[Graeme Nattress]

Aparrant DOF is dependent on a lot of factors, including sensor size and size of the final image. Technically DOF is constant with those factors, but the human visual perception system can be made to think the DOF has changed.

Graeme

 

[Martin Drew]

Mike Curtis had a link at HDfordindies on DOF.

http://www.film-and-video.com/dofmyth.htm

I had seen Walters site ages ago and the DOF myth argument has always bothered me. The focus of a lens is an absolute distance, the DOF is the range of distances either side of that focus distance which will give acceptable focus and as such image magnification is one of the parameters to determine DOF. The example he gives someway down the page illustrates the point. These 2 images are taken with lenses of different focal lengths.

he argues that while the DOF may appear different it is in fact an illusion because if you match the size of an out of focus item in the image between the 2 images you will see that there is the same amount of blurryness on each image. The problem is that if you are magnifying a part of the image you are changing a DOF parameter.

Or am I missing something?

Martin

 

[Júlio Taubkin]

I agree with Martin. DOF is not about what's in focus or not. It's about how far from focus we will still accept and perceive as "in focus". As such, it's dependent of a lot of factors, especially size of final image (or our ability to perceive the full resolution of it). If you take a 4K image and downrez to ntsc, you will gain DOF, because it will be more difficult to realize the small nuances of your DOF. That's why I think that a 2K downrezz image should have a different DOF.

 

[Gavin Greenwalt]

<warning, stupid question> ..Uh, why couldn't the shot just be re-done?

I know, I know... it doesn't always work that way, especially when the decision is made weeks or months down the road. I feel your pain though.

Sky Replacement is a popular 'Fix it in Post' task which often requires the footage to be shot in a way not conducive to a standard FX shoot. And it's usually even decided before they shoot it that way. So it's not so much an "error" as a challenge.

it's also the reason I always take a picture of a good sky when I see it. You never know when it might come in handy later.

 

[Martin Drew]

The CoC will change, but it'll be a linear shift so it won't effect the DoF just the 'focus'. It's like applying a Gaussian blur to a 4k image. The DOF hasn't changed, since everything was affected evenly.

If the circle of confusion changes it will affect the depth of field. circle of confusion is one of the parameters used to define depth of field.

Martin

 

[Hans von Sonntag]

My first Post in this forum so please be patient...

I like to add some practical thoughts to this very interesting 4K vs 2K thread:

One of REDs major advantages over a 35mm camera is not only costs but the possibility to use 35mm and S16 DOF in one camera. For example:

For exterior shots at night it is nice to use available lights and some practicals among extra light-equipment. Therefore I don't need only fast stock (RED is supposed to be 400 ASA as far as I know which is considerably fast even compared to 500 ASA Kodak/Fuji. You will only rarely expose this stock to its full 500 ASA) but also fast primes, e.g. T1.4. This will lead to very shallow focus and on longer shots to a soft, undefined picture. Not necessarily nice. Now I window the sensor to S16 and the focus will be not as shallow. Great.

Next example: I use a short zoom lens, a 5 to 1 Cooke 18-100 for instance - the only lens I have with me. For a certain shot a longer lens would be nice. No, I'm not going to use this extender. It eats 2 stops and messes up the sharpness of the lens. But - I've got RED. I just simply window the sensor and have an almost 2 times closer image. Great.

To come back to the 2k vs 4k business. As long as any decent DI software needs uncompressed video (QT, DPX, etc.) I need a fast raid and a lot of storage to manage even HD. 2K will be possible; I might have to by a new raid though (another 10k). 4K is not possible. Not now, not tomorrow, not for an indie filmmaker in the next 2 years or so.
If one once tackled messy keys (real world greenbox shots are always kind of messy) and rendered them and rerendered them (you hardly render a complex composit only once) knows how long it takes on HD. 4K? Please not. I'm not going to do it.

So dear RED Wizards: Please make REDCODE RAW possible not only for windowed S16 but also 35mm full aperture. I want to shoot all in 2K and just switch the aperture but not the codec. Another plus: I can overcrank the camera up to 60fps which is enough for the most circumstances. 4K is great for the future and its good to know that the investment will hold its value for a longer time but 2K is much more realistic for an indie filmaker to day (and I am doing my stuff to day and not in 2 years). This actually reminds me of the days when I upgraded my old Arri SR from N16 to S16 which added another 10 year of usage.

Hans

 

[Graeme Nattress]

REDCODE RAW works in 4k and 2k modes, so you can leverage it for much cheaper 4k workflows with it's mild, great looking compression.

Graeme

 

[Hans von Sonntag]

Graeme, thanks a lot for your reply!

I suppose I did not understand your chart entirely.

So 2K REDCODE RAW does also work with a non-windowed sensor?

Is REDCODE RAW 4K/2K natively editable in NLE (e.g. FCP) right from the fly?

Does REDCine work like a conforming-tool? Can I put in my 4k/2K REDCODE RAW camera-files and conform via EDL/XML the edited shots into say 2K DPX/ 1080P_QT?

Please excuse me asking questions which might have been answered already elsewhere...

 

[Graeme Nattress]

I think the chart was done before we announced 4k RAW. You can have 4k RAW and 2k RAW both in REDCODE RAW.

Any app that supports Quicktime should edit it straight away.

There is some sort of conform type functionality in REDCINE, and I think you'll find more info on that elsewhere on the forum.

Graeme

 

[Hans von Sonntag]

Thank's a lot! Much appreciated,

Hans

 

[Antoine Baumann]

One of REDs major advantages over a 35mm camera is not only costs but the possibility to use 35mm and S16 DOF in one camera.

I totaly agree with that. I love the possibility to switch between the two format. Also the 2k shooting allow greater frame rates, so for some shots it would be necessary to shoot 2k (you could even need to go down to 720p for 120 fps). That is an other reason that would make you go for a 2k postproduction.

To come back to the 2k vs 4k business. As long as any decent DI software needs uncompressed video (QT, DPX, etc.) I need a fast raid and a lot of storage to manage even HD. 2K will be possible; I might have to by a new raid though (another 10k). 4K is not possible. Not now, not tomorrow, not for an indie filmmaker in the next 2 years or so.
If one once tackled messy keys (real world greenbox shots are always kind of messy) and rendered them and rerendered them (you hardly render a complex composit only once) knows how long it takes on HD. 4K? Please not. I'm not going to do it.

I think you are totaly right about the raid system, and the number of time you need to render a comp, thus the time it would take at 4k, but I am personnaly thinking to stick to redcode rgb for the postproduction work, as long as I can (might be even for color correction). And as redcode is a quicktime codec, it will work in all the softwares supporting them (FCP, Shake, etc...).
I do not see the point (but I am open minded) to use uncompressed tiff, if you shoot redcode. It will be much lighter to use redcode and will save storages acquisition (for exemple the milkgirls 1080 redcode is only around 7.5 MB per second), if the software you use support it of course.

My 2 cents,
antoine

 

[Nick Shaw]

…for exemple the milkgirls 1080 redcode is only around 7.5 MB per second…

7.5MB/s is the data-rate for the MJPEG 1080p Quicktime of the clip available for download, not the datarate of the original REDCODE clip. REDCODE at 24fps is expected to be about 27MB/s (although Graeme has recently said they have improved efficiency since that figure was quoted.)

Nonetheless, I agree that REDCODE will make working with 4k media much more feasible on a 'normal' editing system.

Nick

 

[Rob Lohman]

The 1080 milkgirls clip was not in REDCODE. Otherwise you would've had to install our codec to play it.

p.s. the 27 MB/s number was for REDCODE RAW, not RGB. That might be higher (RGB has 3 times as much data than RAW).

 

[Hans von Sonntag]

REDCODE. Ah I missed something, I suppose. I forgot in my thoughts the possibility to use REDCODE RGB for postproduction which seems to be something similar to that what Cineform is already doing and which obviously is working fine. It will be possible to work with a lot "lighter" files, than for instance uncompressed TIFF, without the downside of non-acceptable compression/colourspace (HDCAM, DVCPROHD, not to mention HDV) which is really great.

Nonetheless rendering a 4K comp to REDCODE will be the same time than rendering to a TIFF-sequence.

A fail-safe Raid will be still necessary in an REDCODE workflow, especially if one thinks about data backup/safety - no 35mm negative to rely upon just some data which can vaporize in a second.

I must say Antoine is right pointing out the overcranking possibilities in the 2K-mode.Yes, 4K is super-great quality-wise but if you want to use the camera in the most flexible and creative mode 2K seems the way to go.

Hans

 

[Rob Lohman]

Rendering times will not be the same for REDCODE vs. TIFF if you have a fast enough RAID setup. If the wait is not on writing the data it's on compressing it. Since REDCODE is wavelet based it requires time to compress versus the non-compressed (normally) nature of TIFF.

The footage I shoot is always immediately backup up onto 2 systems. It would be wise to have at least 1 copy off-site. Then you make a third copy to work on and edit.

For working with high-res footage a fast array will be a must. Werther you also want to include safety in that RAID depends on a couple of things, including money.

As long as my original negatives + NLE projects are safe I can withstand a failure of the RAID array containing the footage.