Lens for Blackmagic Design Studio Camera 4K Plus G2

am going to buy a camera (Blackmagic Design Studio Camera 4K Plus G2) but I need a lens that has a large aperture (f/1.0, 1.8) but can zoom in and out (50-300mm f/1.0 or 1.8 | 20-200 mm | 10-400 mm | etc.). Who can help me please because Black Magic proposed me this: (Panasonic Lumix G X Vario PZ 45-175mm f/4-5.6 ASPH. POWER O.I.S. Lens) I don't want it because the aperture is too large (f/4-5.6). I want one (f/1-1.8) 20-500 mm or 45-200mm.

I hate the AI replies on technical discussions, but here it saves some time on basic physics:

A 45–200mm f/1.8 constant aperture lens for Micro Four Thirds (MFT) would be an absolute monster, even just hypothetically. Let's guesstimate its size and weight, keeping in mind what it would take optically to keep f/1.8 constant throughout that zoom range.


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Guesstimate:

Length: ~28–35 cm (11–14 inches)

Diameter: ~11–13 cm (4.5–5 inches)

Weight: ~3.5–4.5 kg (7.5–10 lbs)



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Why so huge?

At 200mm f/1.8, the entrance pupil = 200 / 1.8 ≈ 111 mm wide. That means the front glass element would need to be at least 112–120 mm in diameter.

That’s roughly similar to a 300mm f/2.8 full-frame lens, which typically weighs 2.5–3 kg—and this lens would need to be zoomable and even brighter at the long end.



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For Comparison:

Canon RF 100–300mm f/2.8 (FF): 2.6 kg

Olympus 150–400mm f/4.5 TC1.25x PRO (MFT): 1.9 kg

Panasonic 35–100mm f/2.8 (MFT): 0.36 kg

Nikon 200mm f/2 (FF): 2.9 kg



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A 45–200mm f/1.8 MFT lens would be physically ridiculous and wildly expensive to make, but it would be a beast for indoor sports or stage work if it ever existed.

I hate the AI replies on technical discussions, but here it saves some time on basic physics:

A 45–200mm f/1.8 constant aperture lens for Micro Four Thirds (MFT) would be an absolute monster, even just hypothetically. Let's guesstimate its size and weight, keeping in mind what it would take optically to keep f/1.8 constant throughout that zoom range.


---

Guesstimate:

Length: ~28–35 cm (11–14 inches)

Diameter: ~11–13 cm (4.5–5 inches)

Weight: ~3.5–4.5 kg (7.5–10 lbs)



---

Why so huge?

At 200mm f/1.8, the entrance pupil = 200 / 1.8 ≈ 111 mm wide. That means the front glass element would need to be at least 112–120 mm in diameter.

That’s roughly similar to a 300mm f/2.8 full-frame lens, which typically weighs 2.5–3 kg—and this lens would need to be zoomable and even brighter at the long end.



---

For Comparison:

Canon RF 100–300mm f/2.8 (FF): 2.6 kg

Olympus 150–400mm f/4.5 TC1.25x PRO (MFT): 1.9 kg

Panasonic 35–100mm f/2.8 (MFT): 0.36 kg

Nikon 200mm f/2 (FF): 2.9 kg



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A 45–200mm f/1.8 MFT lens would be physically ridiculous and wildly expensive to make, but it would be a beast for indoor sports or stage work if it ever existed.

Thanks for your response, I just took the example so vaguely, but what I need is if I could find a background that is a little blurry and can be zoomed in and out easily.

Best you probably can do on a budget is a Canon 70-200 on a speedbooster