Question about resolutions on Gemini with it's taller than standard sensor height

[Aaron Lochert]

I don't have a Gemini or had the pleasure to use one yet.

One thing I was thinking about when discussing resolutions in another thread is this:

According to phfx.com, 5K 1.7:1 uses the full sensor recording area of 5120 x 3000.

If you shoot 5K FF, it's not actually the "full frame". It's named as such to match the aspect ratio 1.9:1 of other RED formats. So then FF doesn't mean anything but 1.9:1, right? But then you have the Raven who's 4.5K FF mode actually does use its full sensor and is not a 1.9:1 format. So what does FF mean? Full sensor recording area or 1.9:1?

So then you have 5K HD, which makes a 16:9 crop of that non-full-frame FF format, resulting in 4800 x 2700. This matches the exact same pixels of other 5K HD formats. But is this important to anyone? No one is delivering 4800 x 2700 projects; if we're shooting 16:9 it's because we're all downscaling to UHD anyway. Since we have the sensor height, why not have 5K HD shoot a 5120 x 2880 extraction and have maximum downscaling ability for UHD?

And then 5K 6:5 actually does use the full height resulting in 3600 x 3000, where other cameras with 5K 6:5 shoot 3240 x 2700.

But then 4K 6:5 does not take advantage of the tall aspect ratio sensor, instead matching other RED 4K 6:5 modes and recording 2592 x 2160. So the difference from 5K 6:5 on Gemini to 4K 6:5 on Gemini is a huge crop.

It's incredibly inconsistent.

Not to mention this has implications with framerate ability. 5K 6:5 on Gemini won't be able to hit the same FPS that 5K 6:5 on the other two DSMC2 cameras can because of the added vertical height. But 5K HD across all DSMC2 cameras will.

Maybe the naming conventions need to change. Or maybe we need a toggle switch between "Maximize Resolution" and "Maximize Framerates," meaning if you enable Resolution, you get access to all the resolutions that make use of as much of the sensor area as possible due to the aspect ratio. And if you enable Framerates, you crop in on the sensor as they're doing now with most of the formats (save for 5K 6:5).

Or maybe we just need the ability to dial in whatever recording area we need and let the camera tell us what the maximum framerate we can do with it.

Or maybe we don't, am I thinking too far into this?

I feel like if I shot with this camera I would just shoot 5K 1.7:1 and take whatever extraction I needed in post to avoid all of the confusion.

 

[Anton Shavlik]

Even weirder is what dimension is considered for 4k :

4k 1:1 is 4320x4320
4k 4:3 is 3840x2880
4k 6:5 is 2592x2160

Maybe red can call formats by "horizontal line count (aspect ratio)" ... it would be much less ambiguous in what it means

4320 (1:1)
3840 (4:3)
2592 (6:5)

Then again, frame rate is based on sensor height...

 

[Aaron Lochert]

Yeah, that is weird too.

And just to throw another wrench into the equation of what the industry is doing, apparently Netflix has approved the use of the Alexa LF at 2880 x 2880 with 2x anamorphics for 2:1 delivery with their "4K UHD" classification, because they're counting total megapixels captured by the camera that make it into the final deliverable. They also approved the use of 3148 x 2636 with 2x lenses for odd case where a 2.39:1 delivery is approved by them.

So apparently as long as a "UHD worth of pixels" (8.29 MP) ends up squeezed into your project you're good. But the end user is only going to see see 3840 x 1920 = 7.37 MP or 3840 x 1600 = 6.14 MP in the end. So what is 4K UHD, really?

¯\_(ツ)_/¯

 

[andrewhake]

I think you are probably thinking a bit too much into it. The amount of formats is a bit strange but probably useful to some people. The different formats are all about the standard aspect ratios people use these days. So if you are setting up to shoot full 5K 1.7, you can also setup guides with the proper crop to make sure you are on target. I own a DSMC2 Gemini, and basically just always shoot at 5K FF. And yes you could shoot at the max 5K 1.7 for the most room to reframe. I'm generally not too worried about having the extra sensor height available for reframing as 5K FF already gives you plenty of room to adjust for a 4k output frame.

4K FF on Gemini is 4096x2160, 4K HD is 3840x2160 as you would expect. But again it doesn't really make much sense to shoot at that format unless you are extremely lazy and don't want to do any reformatting in post. The image quality when going down from 5K FF to 3840x2160 is fantastic.

http://phfx.com/tools/formatCompare...elB=Gemini+5K+S35&formatB=4K+HD&focalLengths=

 

[Phil Holland]

I'm not king of the world, but if I was

FF - Ideally means Full Format per resolution. In a perfect world this would be the DCI 1.9:1 Aspect Ratio for each major step in resolution.
2:1 - Obvious
HD - Obviously should result in 1.78:1 or 16x9 aspect ratio with each step in res.
WS - RED's WS format is a 2.37:1 aspect ratio to maintain a bit of flexibility.

The rest should be self explanatory with 6:5, 4:3, 3:2, 1:1, 4:1, and 8:1.


The only actual weirdness is that 6:5 and 4:3 variance but it makes sense when you consider the 2X and 1.3X anamorphic lenses those formats are designed to cater to.

The other weirdness are the Raven, Gemini, and previous Dragon 6K sensor (though this is not an issue in the current lineup) as it pertains to their Maximum Format. And I say Maximum Format because perhaps MF would "make sense" in that terminology, but unfortunately in the photographic industry MF either means medium format or manual focus.

Perhaps..... Something from the book of motion picture film? Full Aperture sort of makes sense terminology-wise, but not tech-wise. FA?

Or the nutso logic of "Open Gate" perhaps, but that's borrowing from team blue. Maybe Full Gate?

Dunno. Right now it really is only effecting the Gemini, but yeah, would be neato to have something denoting Max Sensor Resolution, erm... Maybe MS?


To a side note, I'm pee-pee pants dance happy that RED has added S35 and VV into the nomenclature as that's a big help.

 

[andrewhake]

Yeah might be able to make things a bit more clear. 5K 1.7 doesn't necessarily imply you should be using anamorphic lenses but maybe some sort of indication that this is the maximum sensor size would be useful. 5K FS (full sensor) or something along those lines. Or Max Sensor as Phil had mentioned. Though Hasselblad started using MS on their Multi-Shot camera. But yeah sensors aren't always going to be a standard industry aspect ratio for various reasons I'm sure.

I do have to say working with the Gemini's 5120px wide sensor and working with the footage on a 5120px wide iMac Pro display is wonderful and I love it.

Too another of Aaron's points. If you choose a format your maximum frame rate will adjust, and if trying to choose a frame rate it is pretty clear if your current format supports it or not so I don't really see that as much of an issue.

 

[Marc Wielage]

And just to throw another wrench into the equation of what the industry is doing, apparently Netflix has approved the use of the Alexa LF at 2880 x 2880 with 2x anamorphics for 2:1 delivery with their "4K UHD" classification, because they're counting total megapixels captured by the camera that make it into the final deliverable. They also approved the use of 3148 x 2636 with 2x lenses for odd case where a 2.39:1 delivery is approved by them.

The Arri website says this:

LF 2.39:1 - 4448x1856

If they used anamorphic lenses, wouldn't they just shoot in open gate 4x3 at 4448x3096 with a squeezed image? What am I missing here?

Alexa LF specs here:
https://www.arri.com/largeformat/

Netflix specs here:
https://partnerhelp.netflixstudios.com/hc/en-us/articles/360000579527-Cameras-and-Image-Capture

If you have another link for anamorphic specs, I'd love to see it to add to our library. I concede these things are practically changing on a week-by-week basis, so it's hard to keep up.

BTW, I would point out that it's getting more important than ever to a) shoot tests and b) shoot framing charts on set so that post is aware of what the DP is seeing in the viewfinder. This is even more important when different cameras are used during production, particularly cameras with different resolutions and pickups.

 

[Aaron Lochert]

I guess that's what I'm getting at. The 1.7:1 sensor kinda puts it in multi-aspect ratio territory, a ratio you'd never actually deliver to, but it's in a happy place between the formats where height is important (6:5, etc), and the wide ones. But then again, that's how we got 16:9 TVs as they were a happy place between 2.39:1 and 4:3 and look where that ended up.

I liked when Mysterium had 4K 16:9 and it meant actually using the full height at 2340 instead of 2160.

I think the term "FF" also could be confused with "Full Frame" as in 135 film. Even though I'd never make that mistake I've definitely seen the confusion on some of the Facebook groups. But I like Max Gate or Full Gate or something.

All I know is I probably spent about 20-30 minutes right now trying to type up the ideal solution, and things got really complicated, really fast. So I feel for what the RED designers have to do to cater to us picky folks.

If you have another link for anamorphic specs, I'd love to see it to add to our library. I concede these things are practically changing on a week-by-week basis, so it's hard to keep up.

BTW, I would point out that it's getting more important than ever to a) shoot tests and b) shoot framing charts on set so that post is aware of what the DP is seeing in the viewfinder. This is even more important when different cameras are used during production, particularly cameras with different resolutions and pickups.

I'm reading this whitepaper.

The section titled "ALEXA LF & 2x Anamorphic Lenses with a 4K UHD Mandate" on page 7 is what I'm talking about. All the way to page 12 covers everything I'm referencing.

Basically it's a way for filmmakers to use Master Anamorphics or other S35-ish format lenses on an Arri camera for Netflix this way, something that Netflix wouldn't have allowed on Alexa previously.

And yes, testing is always, always, important.

 

[andrewhake]

I think to be fair. Arri complicates this stuff MUCH more. I truly don't understand the resolutions they have chosen for their sensors and the mental gymnastics they pull when trying to explain themselves.

Gemini sensor size is in a great place I think. Plenty of resolution to deliver extremely high quality content in any 4096 or 3840 wide format. Which seems that it will be the standard for quite some time now.