Resolution concerns, 2K 4K?

[Álex Montoya]

Stu of The Orphanage already talked about this in his blog. You need a 4k camera to get the perfect 2k image.

And no, Salemas: Jim has stated that he used the RED lenses.

 

[Karl H]

I dont think the lens is a huge factor here as you might think.

My DSLR has a lower resolution CMOS chip and also a $50 lens on it (a 50mm prime). In my opinion so far, it produces clearer/cleaner 4K images than I have seen from the Red camera with any lens on it. As we've said though, this could be more to do with focussing and/or Red Alert settings issue.

edit : exception.. the original milk girls pic was very sharp and clean too!

 

[Graeme Nattress]

The lower the resolution of the CMOS chip, the larger the photosites and the less sharp a lens they need

And as I pointed out, there are vast differences in how the RAWs are developed.... And that we use a OLPF designed to stop aliassing, which is totally unnaceptable in a motion picture, but you "get away with" in stills a little more as you can go and paint out any baddies, which would be a pain in motion.

Graeme

 

[Salem Kapic]

please compare

please compare

Please compare Tonaci image eyes.tiff(4k) and old test frame of girl who blow balloon 4K! (Very similar light condition)

Every image from Tonaci test team is "not in focus" like old Jim's images

 

[Jack Wester]

You see, it takes a 4k camera to get a properly anti-aliassed image at 2k.

Why don't you make more of your posts sticky? You pass a lot of wisdom on this board and it would be sad if it fell into digital oblivium.

In a great deal of the discussions on reduser in the last month (especially in the 2K workflow "wars") this very important fact was often forgotten. Getting the "optimal pixel values" for your output is vital. Otherwise, your output doesn't look as good as your screen/projector has the capability of doing. Any professional graphics designer knows this only to good, but I would guess that a cinematographer in an analogue world, not working at the pixel level on a daily basis, could easily forget the magic of "pixel perfect" images as opposed to just having high resolution.

To me, a megapixel is not publishable as a megapixel if it hasn't been properly downsampled to give each pixel a really good average. Only in a world when sensors are perfect and noice is non existing does your sensor resolution give proper respect to the output resolution.

 

[Joel Kaye]

That said, should it matter if this is motion picture or digital?

You posted a handheld shot at 1/48th of a second for one thing. Most DSLR's sharpen in camera for another another thing. Most DSLR's force a shutter speed higher than the lens focal length to help freeze camera motion. RED can't do that. Camera motion will create the illusion of "soft".

Without a controlled environment test your questions can't be answered.

 

[Graeme Nattress]

A megapixel is purely a measure of the number of photosites that are used to create the image.

As you downsample you push more an more quality and per-pixel resolution into the image - it's like distilling malt - you end up with delicious single malt whisky, but an awful lot less liquid than you started with.

Even if sensors were perfect, you'd still need optical low pass filtering to avoid aliassing. And downsampling cannot remove aliassing that gets into a system at the start because aliassing is indistinguishable from real detail (other than looking "wrong").

Graeme

 

[Karl H]

I think my Canon lenses will be good enough to resolve the full 4K (and I'll be buying more expensive ones too when my Red arrives).

I have to admit, I dont understand the whole process of producing an image from a bayer sensor, I'm only going on what I'm seeing with my eyes.

I know 4K sensor does not equate to a 4K image as RGB needs to be derived from each pixel. Hence my 350D with an image size of 3456x2304 should in theory give out less than a 3.5K image, maybe more like 2K on a resolution chart.

Im still hoping that with mysterium and the correct settings I should be able to get images that are sharper and clearer than what I get from my stills camera. I'm just not seeing them yet, which as discussed could be down to many reasons.

Graeme, is it possible to play with the sharpness during the demoisaic process in RedCine? I, like you, hate artificial sharpening on cheapo video, but whatever canon use it seems smooth but hightly detailed. nothing about it looks artificial.

 

[Karl H]

>>>You posted a handheld shot at 1/48th of a second for one thing.


good point, perhaps some wide shots outdoors at 1/250th will give us a better idea

 

[Matt Uhry]

The lower the resolution of the CMOS chip, the larger the photosites and the less sharp a lens they need

Graeme

What would be a good target of LP/MM as seen on a lens projector for getting 4k out of a Mysterium?


Matt Uhry
www.mattuhry.com

 

[Jack Wester]

I guess I'm saying the obvious, but an unsharp edge of 20 pixels in a micro perspective is just a gradient between two sets of values. And downsampling and upsampling a gradient would not cause great damage to the image.
Depending on the upsampling method a perfect gradient would actually upscale to a mathematically indentical image.

Simply zoom down to the sharpest and most focused detail on the image and count the number of pixels forming the edge to see of it's sharp enough for the kind of experiment discussed in this thread. The image at hand in this thread is far from a good candidate. The Dickies logotype from the milk girls is a much better subject. I'm sure that with optimal focus and lighting conditions, even bigger differences would be evident.

 

[Karl H]

The image at hand in this thread is far from a good candidate.

I know, dont keep reminding me but it has brought up an interesting discussion!

One thing I never thought of was the amount of sharpening thats acceptable in a still image. Of course when that's moving you might get some sort of 'shimmering' effect, and so Red has to use much less sharpening processes than a still camera.

To me it doesnt look like sharpening in my still images as im processing these also from RAW files; it looks like more resolution. Like everyone here I WANT to see something that will dissolve my concerns. Maybe some sharp 4K images in the coming weeks will shut me up!

In all honestly I have some really bad DSLR pics that I could compare this too aswell, so it isnt fair perhaps to compare this handheld 1/48th second indoor shot (possibly pushed in post too).. to a 1/400th second outdoor crystal sharp image:sarcasm:

 

[Jack Wester]

The difference between 2K and 4K is actually bigger than what this example shows. The 2K on the left was downsampled from 4K before it was upsampled. So the 2K image shown have better pixel averages and less noise (even if noise under this lighting conditions would be very low) than what would be the case if it was captured at 2K by the sensor.

EDIT - The conclusion is this. We REALLY benefit from 4K even if we're producing 1080p.

 

[Karl H]

I see what you're saying. You need a 4K sensor to derive a 2K image. If Red had a 2K sensor then the image would never have been close to 2K in real world resolution.....but as it relates to recording 4K, are we saying the resolution difference between the two is not THAT critical. Certainly not a visable 4x resolution difference.

If I understand Graeme corectly, we're probably geting a real world resolution from Red's 4K bayer of around 3K? If thats the case, why dont we have a 3K recording option and save some bandwidth? ;-) or alternatively turn up the bitrate so we get better quality compression at 3K.

 

[Graeme Nattress]

Darkline, yes you can play with both detail extraction and "sharpness". You'd probably measure around 2.5k on your camera, depending on the strength of the OLPF and how the detail extraction is done on the bayer pattern.

Remember, a lot of these images we're looking at are at a slow shutter, and wide open - hardly a recipe for sharpness.

I've not found any lenses I've used to be limiting resolution yet, Matt.

 

[Graeme Nattress]

Darkline, if only it were so simple.....

The measured resolution from the 4k is over 3k, but say we downsampled it to 3k, we'd now need to be in RGB, not raw, and therefore the file size just got bigger, not smaller. Downsample to 2k, and you've got a 2k full of nearly 2k resolution, but the file size is 3/4 of that of the 4k and you've lost 1k of resolution for that. That's why 4k is best recorded as 4k.

Graeme

 

[Jack Wester]

I see what you're saying. You need a 4K sensor to derive a 2K image.

If a pixel recorded by the sensor contains an edge within its boundaries and the sensor would report a pixel average that properly takes and average of all things going on within that pixel boundary, you could argue that 2K would give you 2K, but in the real world, this does not happen. A sensor would never give you such a good pixel.

If you, however have 4 pixels to begin with, or even better 16 pixels, your downsampling would convert those pixels to a single pixel with a very representation of what was going on within that small rectangle of light by calculating the average of those 4 or 16 pixels.

If the optics and focus would not be the bottleneck, a 4K image would look better on an 8K or even a 16K sensor.

If I'm allowed to dream and guess, I'm sure that even if projectors does not go beyond 4K, Red would create for us an 8K sensor in the distant future, To go beyond that would probably mean manual focus combined with automatic finetuning to squeeze out that last bit of focus. That would look better in 4K than 4K looks today.

 

[Graeme Nattress]

Jack, downsampling reduces noise, but what you're not talking about is aliassing. If you put a > 4k resolution into a 4k sensor, you get aliassing, and that's nasty and not removable by downsampling. That's why we only get >3k out of the 4k as we're low pass filtering the image. I wish you could get "brick wall" optical low pass filters, but you can't, so we have to start filtering early to stop bad aliassing. That's the way of life for the moment for all sensors.

But, when you downsample, you can use digital filters with a very defined bandwidth that can push a lot more resolution into the downsampled image than what you'd get with optical filtering. And you get lower noise (as you have larger effective pixels).

Graeme

 

[Jim Arthurs]

I'd sure not be too concerned at this point... look to the example image from JJ to get a glimpse of what sharpness can be with this camera... while we'd love to see the full 4K of it, I've no doubt there are great advantages to recording 4K no matter what the actual resolution... it's certainly in the 3K or greater range and that's just fine... gives you all the VFX and re-framing wiggle room you need for a stunning 2K final.

So far, the test team images have just proven how spot on you have to be with critical focus with this camera... I predict a great deal of folks that were jonesing for an eyelash wide sliver of depth of field will be very soon learning to love f11-f16 work simply to protect their hineys on jobs!

BTW, we've covered most of this in a very old thread, where Graeme details (no pun intended) all the benefits of the 4K original solution, then we go rounds on how we want to work for finals... I argue the very point of this thread... that 2K from 4K is the sweet spot of this camera, but it's a manly full-bodied 2K dripping with saturated resolution... not the whimpy 2K from current cameras!

http://www.reduser.net/forum/showthread.php?p=1365#post1365

Besides, I have to remind... if it wasn't for RED we'd be hanging on every detail of what ever incremental feature upgrade Panasonic would be delivering for whatever replaces the HVX or the like from Sony... here we're just arguing the degree of superiority over all other potential solutions at ANY pricepoint.

 

[Evan Owen]

Like several have already mentioned, focus is critical at 4K. I've noticed that quite a few of the shots so far have been a little out of focus. Once Graeme's focus assist is operational, I'm sure that will be minimized. Until then, we'll probably continue to see soft images for awhile.

I found one of the sharpest images so far on www.fxguide.com (article here). Scaling to 2K and back up reduced the detail substantially. If you're careful with the focus, 4K is worth it.