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Andrew Reid

BMCC variant Metabones Speed Booster works on GH3 and GH4 to give 1.28x crop, almost full frame look!

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BMCC Speed Booster on the GH4

I had hesitated to try this for so long, but finally today a brave EOSHD reader sent me a tweet saying he had fitted his BMCC Speed Booster (with protruding rear-glass) on his GH4. It just goes straight on. First a BIG disclaimer. Speed Booster adapters have adjustable glass which can sit closer or further away from the sensor to fine tune infinity focus. On some adapters this will mean potentially it will clash against the inner housing of the mount and be damaged if used on a Micro Four Thirds stills camera. Therefore I do not take responsibility for any loss or damage if you try this.

Read the full article here

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Great, I thought the image circle wouldn't cover m43. They should make a 2x scaled version of it for the A7s -> medium format.

 

I wonder what will happen to the specific gh4 speedbooster if this turns out to work fine.

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On the term "full frame look". Note, that with any focal reducer the angle of view widens, but the depth of field *doesn't change* at all. A 2.8 looks different in Super 16, MFT, APS-C and Full Frame. That's why the biggest problem with GH4 is it's relatively big DoF - relative to the resolution. The only way to overcome this problem are very fast lenses, not Speedboosters.

Let me explain further: It's true, high resolution will add shallowDoF to some extent, because the >circles of confusion are smaller (are they though? Are the pixel dimensions different from, say, those of the GH3?), but generellay, if there was an aesthetic benefit of 4k over HD in the first place, it had to do with selective sharpness, not with infinite detail. The existing UHD camcorders with small sensors prove that, the images look terrible.

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Axel, the widening of the field of view allows one to move the camera closer to fill the frame and this reduces the depth of field.

The depth of field a lens and sensor combination can create is at it's maximum at minimum focus distance.

With smaller sensors that result in larger crop factors, like the GH4, a 50mm full frame lens gives a Fullframe field of view of 100mm.

Let's bring this into the real world of cinematography: if I use my Panasonic GH4 to shoot a close up dialogue scene with an adapted Sigma 35mm f/1.4 I get a field of view of 70mm, perfect for a proper 'head and shoulders' close up.

A 35mm even at f/1.4 is no bokeh monster, especially on a m43 sensor, so by using the Speed Booster on the 35mm f/1.4 I gain .71x in field of view and one stop of light, so now it's an effective 49.7mm f/1.0 instead of 70mm f/1.4.

Now I can lower my ISO one stop to maintain the exposure and lower noise without penalty AND I'll reframe by moving the camera closer, thus nearing the minimum focus distance. This results in a decrease of the depth of field.

If I didn't want to move the camera I could also use a Sigma 50 f/1.4, which would normally be a 100mm field of view, but with the Speed Booster, to becomes an effective 71mm f/1.0, extremely close to the previous 70mm effective view with the Sigma 35mm f/1.4 (without booster). But now I have increased the focal lengthy optically, thus decreasing the depth of field.

The Speed Booster opens up many avenues for low-budget film projects.

I can keep noise much lower by using optically fast lenses to reduce the ISO.

I can lower the power level from external lighting like LED panels and save battery life or reduce heat buildup from HMIs thanks to the faster apertures.

I can use incredibly fast, light gathering T-stops with no danger of approaching the ridiculously thin full frame depth of field that only results in most things annoyingly out of focus. Yet I can still enough beautifully blurred foregrounds and backgrounds.

I can regain and harness some of the lens character that's lost due to the 2x crop that only uses the 'sweet spot' center. Sometimes the lens edges add to the cinematic feel.

If the BMCC Speed Booster usage on the GH4 is worked out and deemed safe, all the above applies still and is improved upon.

These are exciting times to be in cinematography.

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I'm sure youre mistaken there somehow Axel. The only reason there's a DOF difference is because when using the same lens on different sensor sizes, you have to stand closer or further back to get the same frame. And of course when your distance changes, so does the amount of background blur.

 

 

If at 4k the GH4 with BMCC Speed booster has a 1.4x crop, then does that mean it could still possibly work with the Sigma 18-35mm? That would be sweet.

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Andrew, you well know I am an admirer and defender of your web corner outside of here and here is the proof, the way you end your article:

 

"For now I recommend sticking with the official Micro Four Thirds Speed Booster if you’re a GH4 owner! This still gives you a approximately Canon APS-C sized 1.56x crop rendering of your full frame lenses and is a perfect match to APS-C lenses like the Sigma 18-35mm F1.8."

 

Where you, after so much experimentalist craziness :D you end with the wisest advice on topic ;)

 

Frankly, no idea why your naysayers go to pick up so much hate to spread wherever they can... your resources are becoming the most interesting location for indie filmmaking along dvxuser.

 

E :-)

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On the term "full frame look". Note, that with any focal reducer the angle of view widens, but the depth of field *doesn't change* at all. A 2.8 looks different in Super 16, MFT, APS-C and Full Frame. That's why the biggest problem with GH4 is it's relatively big DoF - relative to the resolution. The only way to overcome this problem are very fast lenses, not Speedboosters.

Let me explain further: It's true, high resolution will add shallowDoF to some extent, because the >circles of confusion are smaller (are they though? Are the pixel dimensions different from, say, those of the GH3?), but generellay, if there was an aesthetic benefit of 4k over HD in the first place, it had to do with selective sharpness, not with infinite detail. The existing UHD camcorders with small sensors prove that, the images look terrible.

Fullframe look is perfectly fine because what focal reducers do is compressing the image circle,or virtually scaling up the sensor.

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On the term "full frame look". Note, that with any focal reducer the angle of view widens, but the depth of field *doesn't change* at all. A 2.8 looks different in Super 16, MFT, APS-C and Full Frame. That's why the biggest problem with GH4 is it's relatively big DoF - relative to the resolution. The only way to overcome this problem are very fast lenses, not Speedboosters.

 

FALSE! 
You sir, have missed the beauty of the focal reducer concept! It shrinks the entire image circle of light that was intended to cover a full frame sensor, giving you the similar FOV and DOF! You see what a sensor of that size would see, plus an extra light gathering stop because the photons are now condensed. 

 

Lenses become wider AND faster (and in many cases sharper because the imperfections are shrunk as well). It sounds like science fiction, but its just science!

 

I'm speaking from personal experience with these as well as from a physics perspective, THE DOF DOES IN FACT CHANGE.

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FALSE! 
You sir, have missed the beauty of the focal reducer concept! It shrinks the entire image circle of light that was intended to cover a full frame sensor, giving you the similar FOV and DOF! You see what a sensor of that size would see, plus an extra light gathering stop because the photons are now condensed. 

 

Lenses become wider AND faster (and in many cases sharper because the imperfections are shrunk as well). It sounds like science fiction, but its just science!

 

I'm speaking from personal experience with these as well as from a physics perspective, THE DOF DOES IN FACT CHANGE.

You know you can also introduce colour as well as caps capitals and bold. This helps to get the point across even betterer.

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I'm still debating which Speedbooster to get for my GH4.  I have good Canon FD and some Nikon glass, but I'm not sure I want to use either of these options boosted.  

 

I'm leaning Nikon, but if an EF booster comes along I may sell a bunch of lenses and go that way.   Like Ben Corwin said,  I'll wait it out a bit longer. 

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@dishe, Orangenz, araucaria, Inazuma:

 

Maybe you're right. I just always felt that nothing could reach the sDoF (and quality of bokeh) of a fast lens on a 5D, for instance. I have the M-SB too.

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