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    #41
    Senior Member ahalpert's Avatar
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    Quote Originally Posted by combatentropy View Post
    And focal distance. If you focus the lens on something far away, the depth of field is deeper than if you focus on something up close. That's why the old cinematography depth-of-field charts included focal distance (example).

    For example, if you focus on something 6' away, your DOF might be 3'. But if you focus on something 16' away, your DOF might be 10'.

    Each lens has a certain focal distance where DOF is at its maximum. Some people might think it is when you set the lens to infinity, but actually it is a little bit less than infinity, and it is called the hyperfocal distance.
    sure but that isn't really dependent on the specific lens design beyond focal length and aperture. so - while you might need to look it up in a chart - labeling the lens's DOF in some way would just mean you don't have to look it up. focusing farther away yielding more DOF is also independent of optic


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    Oh, I see later you say:

    I could see an additional figure being offered. A number that indicates how much DOF there is at maximum aperture and a fixed distance


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    #43
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    Quote Originally Posted by morgan_moore View Post
    MItch - the poor performance of this lens is due to its age and SD ness or due to some form of compensation for three chips?

    Maybe a properly designed doubler would be 'cheap'

    ENG lens on FS7 with glassless converter..

    Poor performance could be due to a number of factors. First off that model was a fairly cheap industrial lens, not a high end performer. It was designed for SD, and HD intended lenses are of far greater quality. In fact I'm not sure that particular SD lens was even designed for 16x9 coverage. If it is an old 4x3 lens then that would help explain the vignette on the wide end as well as the overall low performance.
    Mitch Gross
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    #44
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    Quote Originally Posted by ahalpert View Post
    Speak of the devil - Zhong Yi just announced a UHD B4 to M43 adapter/doubler. About 1lb $1k

    https://www.43rumors.com/zhong-yi-op...nder-released/
    This looks like a Chinese copy of an IB/E HDx2.
    Mitch Gross
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    #45
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    Quote Originally Posted by morgan_moore View Post
    THis looks good - at 1lb five elements and designed for the job it should be better than the internal dubler.

    ONe thing Im not up to speed on is the 2/3 lenses are (or are not??) landing the coloured light at different planes to function with three chips. (This would cause colour fringing on a single chip - my 'film' was abound with colour fringes amongst many abberations)

    Maybe Mitch would be kind enough to chip in.
    Due to the physics of a prism and mechanical manufacturing needs, B4 mount 2/3" lenses are not deigned to focus different parts of the spectrum on the same focal plane. While the differences are measured in microns, it's certainly enough to cause excessive color fringing and chromatic aberration if not compensated for with proper optics. The IB/E optical adapters account for this and compensate for the differences in the spectrum focal distances. I can't speak for other optical adapters as I dont have detailed personal knowledge, but I can tell you that using a lens with just the internal doubler will not be properly collimated due to this issue.
    Mitch Gross
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    #46
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    On the question of what magic happens to depth of field with the use of these optical adapter, the answer is simple. The original B4 mount zoom is unchanged so the relative depth of field it wold render when used in its native 2/3" is the same as when adapted and used in S-35. Physics.
    Mitch Gross
    NYC


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    #47
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    Quote Originally Posted by Mitch Gross View Post
    This looks like a Chinese copy of an IB/E HDx2.
    I'm curious to see if it is a simple 2x teleconverter or if it does account for the differing focusing points for each color and the super thick glass of the prism block.

    Because it's not just the differing focus points that need to be accommodated for when adapting B4 lens, the light is also focused through a whopping 46.2mm of glass (prism and filters) before it hits the sensor: https://tech.ebu.ch/docs/tech/tech3294.pdf . If you don't correct for that you get massive spherical aberration. You can see a good example of what that looks like here: https://cinematography.com/index.php...bloom-mystery/ .

    Metabones, for instance, has different Speed Boosters for only a 1.6mm cover glass thickness difference, so 46.2mm is massive. (Panasonic has 4mm thick cover glass, while a lot of Blackmagic cameras have a 2.4mm cover glass thickness).

    I own the IB/E HDx2 Mark II and it is lovely.

    I did want to point out, though, that the HDx2 Mark II is 5 elements in 2 groups, with 7 total glass surfaces. It's also designed to be used on PL mount cameras, so the lenses are not going as close to a m4/3 sensor as they could be.

    This lens goes all the way to the rear of the m4/3 mount and is 8 elements in 5 groups, with 12 total glass surfaces. It may very well be better than the HDx2.

    This does not look a copy of anything. If they wanted to copy something, it would most likely be the 2x teleconverters that Olympus and Panasonic already make. Their optical formula (https://www.newsshooter.com/wp-conte...t-10.01.54.png) doesn't match those of Olympus and Panasonic: https://www.four-thirds.org/en/microft/accessories.html .

    I also don't think one should go straight to using the term Chinese copy. There are some very unique lenses coming from a variety of manufacturers based in China. I just today got in a Meike 28mm f2.8 lens and it is absolutely lovely - no plastic at all (even the lens cap is metal) with clickless aperture and it seems very sharp so far with nice bokeh and very little vignetting on m4/3. And the kicker - it was only $50. I could have spent over half of that on just a step up ring. If I had paid $150 for that lens I would have felt that I got a good deal. I specifically needed a super small front element lens for combining with an anamorphic adapter and this fit the bill better than anything else out there.
    Last edited by Joshua Cadmium; 09-30-2020 at 11:22 PM.


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    #48
    Senior Member ahalpert's Avatar
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    Wow re:Meike. What anamorphic adapter are you using? The Anamorphot?


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    #49
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    I'm using a larger Isco projector attachment with a one-off variable diopter. I'll post a write up at some point, because a lot of what I have is not documented anywhere, but I'm not quite ready yet.


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    #50
    Senior Member Harry Pallenberg's Avatar
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    hmmmm... less than inspiring. Hope the info is wrong. https://www.43rumors.com/leaked-spec...h1-mft-camera/

    The main specifications of Panasonic’s cinema 4K box camera “LUMIX BGH1“
    10.28 million effective pixels Four Thirds sensor
    Micro Four Thirds mount
    C4K60P 4: 2: 2 10-bit RAW video (HDMI output)
    C4K60P 4: 2: 0 10-bit (H.265 / HEVC) Internal recording
    dual native ISO
    Double SD card slot
    Wi-Fi / Bluetooth
    11800mAh VBR battery compatible
    size 93.093.0x78.0mm
    weight 545g (main unit only)

    No 10bit 4:2:2 internal? No ND? No 4K120? No so much more?
    Thanks,

    Harry
    Sunny & Mild Media


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