M42 lenses on Blackmagic Production Camera 4K

Hello,
I'm living in Poland, and i found in my grandsfather basement m42 lenses, mostly soviet types:
Jupiter 37a 135mm f.3.5 and 2x Helios 44M - 58mm/f.2, 2x Pentacon 85mm f2.8. Probably never been used. I mounted lenses using m42 adapter (m42 to EF) on my BMPC 4k, but... What is the really crop factor??

BMBP 4k has 1.6x crop factor including all types of lenses?

58mm x 1.6 is ~ 93 mm on bmpc 4k
135 mm x 1.6 ~ 216 mm on bmpc 4k
85mm x 1.6 ~ 136 mm on bmpc 4k

It's true? What about "f." ?
Thanks!

No change for the f-stop, but small correction: the horizontal crop factor for the sensor while shooting raw is 1.7x.

4000 photosites X .0055 microns = 22mm
36 / 22 = 1.7x


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No change for the f-stop, but small correction: the horizontal crop factor for the sensor while shooting raw is 1.7x.

4000 photosites X .0055 microns = 22mm
36 / 22 = 1.7x

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So my m42 58mm lens mounted on bmpc4k really has (58x x1.7) ca. 99mm in RAW mode? What about ProRes 422?

Thanks Rick!

Hey, I must be drunk. The 1.7x horizontal crop is for ProRes 422 UHD 3840x2160 with an active sensor window width of 21.12mm. My apologies and I haven't even had a single drink! The horizontal crop for raw 4000x2160 with a sensor width of 22mm is 1.636x. Too many numbers to keep in my head. Next time I'll use the calculator.


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So my m42 58mm lens mounted on bmpc4k really has (58x x1.7) ca. 99mm in RAW mode? What about ProRes 422?

Crop factor will be the same whither shooting Raw or ProRes, it is the sensor size that determines the sensor crop factor not the codec being used. That said, forget about using it, unless you are trying to match shots with different cameras. The BM Production camera is basically a Standard Cine 35 size sensor, so a 30mm lens is the "Normal" 45-degree field of view lens, and 25 and shorter are wide angle, whike 50mm and longer tele. lenses. There is an application called AbelCine that displays the image FOV of different camera/lens combos to help you visualize this.

Denny, on the BMPC4K, the active sensor size does vary depending upon whether you are shooting raw 4000x2160 or ProRes UHD 3840x2160, hence the different crop values of 1.636x and 1.7x.


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Oops, Rats, a Senior moment flag! I forgot that the Production camera is a windowed ProRes in UHD crop of full sensor. My bad. Walking away, lights fade to black, while whistling to myself....

Actually, since I wasn't drunk, I too had a senior moment when confusing the crop factors in the earlier post. Kinda nice isn't it to know we really are brilliant and any errors and malfunctions are temporary glitches only. I understand at some point senior moments can last longer than a 'moment' but let's not go there while we're having so much fun here.


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Those are some stunning lenses you've found. Don't worry about the crop. That's only in comparison to a full frame sensor, so Arri alexas, red epics etc have between 1.3 - 1.5 crop and believe me people who use those cameras don't give a rats about the crop factor, they just pick the lens they want for the job they want. Really simple to use on the ef as well. I've got some and have them with adaptors that cost a few pounds. Love em.

Those are some stunning lenses you've found. Don't worry about the crop. That's only in comparison to a full frame sensor, so Arri alexas, red epics etc have between 1.3 - 1.5 crop and believe me people who use those cameras don't give a rats about the crop factor, they just pick the lens they want for the job they want. Really simple to use on the ef as well. I've got some and have them with adaptors that cost a few pounds. Love em.

Michael thanks! believe me i dont care about the crop, lenses are great. My question is beacuse of my own curiosity only

I have Helios 44M on my BMPC. Works great with some China adapter ring.