Thread: Shooting 240fps on the Gemini - Lens question?

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  1. #1 Shooting 240fps on the Gemini - Lens question? 
    Hi there, I've got a shoot coming up where we need to utilize the 240 FPS of the Red Gemini Ranger that the production has. They have the Sigma Cine zooms in PL available.

    I know it will crop the sensor a bit, and lowers the max resolution, but can this be offset well by using a super16 lens?

    Any insight is appreciated. Or other lenses that hold up very sharp when cropped in like the Gemini will be. The high frame rate is key, but getting as best footage with that high frame rate obviously a must.

    -Wes
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  2. #2  
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    I presume you mean compensate for the 2K crop factor/FOV by using wider lenses. Yes, you can! Gemini at 2k (which is what you'll need to be at for 240fps), is ~s16 in size, so S16 lenses should cover.

    That being said, if you're used to 5k>1080p, the 2k>1080p comparatively looks like mush (especially if the glass is soft/vintage). You'll probably wanna do a quick test to see how the lens+resolution combo looks, and then let the client decide if it's adequate enough.

    Also bare in mind that focal lengths/FOV are the same regardless of coverage; so a FF35 Sigma zoom at 18mm will be the same FOV as a s16 lens at 18mm... In other words, it might be pointless to use older/softer s16 glass unless you're actually getting something wider than the widest Sigma you currently have access to (like an 8-64mm S16 Canon or something).
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  3. #3  
    Like Mike said I would avoid 2K unless you want a softer grainier look. If you do shoot in 2k the main thing is having the most razor sharp lenses possible. Those Sigma's are pretty dang sharp.
    Mike McEntire
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  4. #4  
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    Get the sharpest and fastest lens you can afford(prime in the right focal length).
    Lenses tend to be the sharpest in the middle.
    Here is a list of some (photo) lenses and their MTF https://www.the-digital-picture.com/Reviews/MTF.aspx (Sigma primes are pretty good).
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  5. #5  
    Senior Member Nick Morrison's Avatar
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    Yes S16 glass will cover Gemini 2K, they are the right match, but I think you'll find a lot of that glass isn't very sharp - at least wide open.

    We got burned once shooting S16 Super Speeds wide open @2K on Dragon, and it was very soft. Almost unusable. We realized we were better off useing S35 or FF glass wide open.

    You're better of shooting on the Sigmas as they are very sharp even wide open.
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  6. #6  
    Quote Originally Posted by Nick Morrison View Post
    Yes S16 glass will cover Gemini 2K, they are the right match, but I think you'll find a lot of that glass isn't very sharp - at least wide open.

    We got burned once shooting S16 Super Speeds wide open @2K on Dragon, and it was very soft. Almost unusable. We realized we were better off useing S35 or FF glass wide open.

    You're better of shooting on the Sigmas as they are very sharp even wide open.
    Thanks, I think we will rent some Ultra Primes so we can get a leg up on the sigmas. Appreciate the insight into the softness with s16 lenses at 2k - unfortunately 2k is how it has to be because client is looking for that super slow motion and we don't have phantom rental budget. I was quite surprised at how high the day rentals still are for phantom cameras in NYC
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    Senior Member Michael Lindsay's Avatar
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    If you really have to use that little of the sensor consider zeiss ultra 16 lenses...

    They blow away ultraprimes when on wider focal lengths..

    They are razor sharp and tuned for small!
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  8. #8  
    Senior Member Nick Morrison's Avatar
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    Quote Originally Posted by Wes Van Heest View Post
    Thanks, I think we will rent some Ultra Primes so we can get a leg up on the sigmas. Appreciate the insight into the softness with s16 lenses at 2k - unfortunately 2k is how it has to be because client is looking for that super slow motion and we don't have phantom rental budget. I was quite surprised at how high the day rentals still are for phantom cameras in NYC
    I actually don't think Ultra Primes are sharper than Sigmas. Especially at T2. Remember the Sigmas are T1.4, and already very sharp. At T2 they are probably close (or maybe even equal) to Master Primes.

    No disrespect to Ultra Primes. They are amazing. And have a great "look" too (a separate convo). But Sigmas are brand new, computer designed lenses and they just very very sharp.
    Nick Morrison
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  9. #9  
    Senior Member Nick Morrison's Avatar
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    Quote Originally Posted by Michael Lindsay View Post
    If you really have to use that little of the sensor consider zeiss ultra 16 lenses...

    They blow away ultraprimes when on wider focal lengths..

    They are razor sharp and tuned for small!
    At wide focal lengths this is a really good idea Michael.
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    Depending on the parameters of the shoot, I'd just go widescreen 3K, and get the bump in resolution. Unless, the shot doesn't last long, or is for 720p broadcast, insta-story, etc. There is a misconception that 2K raw is 2K color output. 2K raw is barely 720p in color video output. But 3K with good light and a sharp lens will give 90% of the frame rate, and give good HD/2K.

    I do wish that RED would have a 2880 pixel horizontal crop option...

    ...that would theoretically give a perfect HD downsample with 1.5x's resolution, while maximizing the highest frame rate possible for slomo. 3K doesn't down sample perfectly, or any better than 2.7K/2.8K. But those couple hundred scan lines could offer a bump in frame rate. But that is all splitting hairs. would be cool though, to have resolutions based on final outputs, rather than arbitrary K's

    in any case, I tend to shoot 3K for high frame rates, unless the image quality is not as importatnt as 240fps or 300fps.

    200 fps at 3K 2.4:1 (3072 1296)

    2.5K looks better than 2K, and I think you can still get around 240fps in WS crop. Which isn't always helpful in 16:9 projects.

    It is kind of a Goldielocks scenario though. 2.5K is too low res for HD projects, and 3K is higher than needed and reduces the max frame rate. 2.8K would be juuuuuust right.
    Last edited by James Sielaff; 09-22-2020 at 12:15 PM.
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