GH4 BMCC Speedbooster & GH4

Samuel H said:
if that's just a cosmetic scratch and is caused by a metal part and not the actual glass in the speedbooster, it's a very minor problem

now, for some math, to see if this helps me warm up to the GH4...

* the sensor is 17.3mm wide, which means a 2.08x crop factor (I always use the horizontal measure only; it doesn't make sense to recalculate the crop factor if I crop the image vertically, say, for a 2.35:1 finish)
* the sensor is 4608 pixels wide, which means 2.34x crop factor shooting 4096 and 2.50x crop factor shooting 3840
* the standard speedbooster is 0.71x which makes those crop factors 1.66x and 1.77x
* the BMCC speedbooster is 0.64x which makes those crop factors 1.50x and 1.60x

The GH4 with a BMCC speedbooster plus Tokina 11-16, Sigma 18-35, Sigma 50mm Art, and Samyang 85mm, is a very compelling <$5K set.
In FF equivalent for FoV and DoF, that would be a 18-26mm f/4.5, 29-56mm f/2.8, 80mm f/2.2, and 135mm f/2.2.

Has anybody tried these lenses with a m43-to-Nikon speedbooster?
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Barry Green just wrote about this on another thread

http://www.dvxuser.com/V6/showthrea...eld-of-View-(Sigma-18-35mm-f1-8-Speedbooster)

If I understood his rationale correctly, here are is what his calculations would be on the Sigma + BMCC Speed booster;

18 x .64 (BMCC Speed booster Focal length multiplier) = 11.52 mm x 2.0 (GH4 Crop factor) = 23 mm FF equivalent

35 x .64 (BMCC Speed booster Focal length multiplier) = 22.40 mm x 2.0 (GH4 Crop factor) = 45 mm FF equivalent

Not too mention the extra stop of light

I actually prefer the multiplier you get out of the regular M4/3 Speed Booster, it gets you a 26mm - 50mm FF equivalent zoom lens with prime lens apertures. You could essentially replace a 25mm, 35mm and 50mm set of FF fast primes....for $800 + $400 for the Nikon Speed booster.....not a bad deal, lol!
 
First: the GH4 crop factor is not 2.0x, unless you are going to shoot in that soft 1080p mode that nobody seems to care about.

And then: he's right, he speedbooster is a focal reducer (it doesn't make the sensor bigger, it reduces the focal length of the lens and increases its aperture in relative terms, i.e., lower f/ number). But for me it's much easier to think about the speedbooster as making your sensor bigger. Full explanation below.


There are two ways to think about a speedbooster:

* "it makes my sensor bigger": this is the easy way to think about it, and the one I use all the time; my APS-C camera becomes FF, and ISO is doubled, end of story. Now I know how a 35mm will look when set it at f/2.8, both in terms of FoV and DoF. Easy.

* "it changes the focal length and aperture of the lens": this route will mess with your brain pretty badly, at least until you get used to it... but it's the correct one, I'm afraid. The sensor is not getting bigger when you put a loupe in front of it. What's happening is that your Samyang 35mm f/1.4 (12 elements in 10 groups) is turning into a 25mm f/1.0 (16 elements in 14 groups). The combination of the lens+SB is indeed 25mm, and it is indeed f/1.0 (the physical size of the aperture hasn't changed, the focal length has, so the ratio becomes 1.0). Exactly the same as when you zoom with your 18-55 f/3.5-5.6 kit lens: glass elements move and this changes focal length, the aperture hole changes size but not much, and f/ is altered; the sensor doesn't get bigger or smaller.

The second one is the correct option... but the first one is way simpler to think about.

This is the article that convinced me to buy one for may NEX-5N: http://www.lensrentals.com/blog/2013/01/metabones-magic
 
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Samuel H said:
First: the GH4 crop factor is not 2.0x, unless you are going to shoot in that soft 1080p mode that nobody seems to care about.

And then: he's right, he speedbooster is a focal reducer (it doesn't make the sensor bigger, it reduces the focal length of the lens and increases its aperture in relative terms, i.e., lower f/ number). But for me it's much easier to think about the speedbooster as making your sensor bigger. Full explanation below.


There are two ways to think about a speedbooster:

* "it makes my sensor bigger": this is the easy way to think about it, and the one I use all the time; my APS-C camera becomes FF, and ISO is doubled, end of story. Now I know how a 35mm will look when set it at f/2.8, both in terms of FoV and DoF. Easy.

* "it changes the focal length and aperture of the lens": this route will mess with your brain pretty badly, at least until you get used to it... but it's the correct one, I'm afraid. The sensor is not getting bigger when you put a loupe in front of it. What's happening is that your Samyang 35mm f/1.4 (12 elements in 10 groups) is turning into a 25mm f/1.0 (16 elements in 14 groups). The combination of the lens+SB is indeed 25mm, and it is indeed f/1.0 (the physical size of the aperture hasn't changed, the focal length has, so the ratio becomes 1.0). Exactly the same as when you zoom with your 18-55 f/3.5-5.6 kit lens: glass elements move and this changes focal length, the aperture hole changes size but not much, and f/ is altered; the sensor doesn't get bigger or smaller.

The second one is the correct option... but the first one is way simpler to think about.
Click to expand...

It's not really accurate to say that 2x isn't the crop factor on the GH4. I am going to bet that a very large percentage of users are going to shoot in 1080 modes and for those people a 2x crop factor is very relevant.

I only displayed the math for 1080, obviously the 4K crop factor is different (2.3x), but the basis for the math is the same, here it is

Sigma 18-35 mm + BMCC Speed Booster, FF equivalency calculations;

18 x .64 (BMCC Speed booster Focal length multiplier) = 11.52 mm x 2.3 (GH4 Crop factor) = 26.5 mm FF equivalent

35 x .64 (BMCC Speed booster Focal length multiplier) = 22.40 mm x 2.3 (GH4 Crop factor) = 51.5 mm FF equivalent

Still an extremely useful lens at 4K, but it's easy to see why people prefer shooting video on their iphones and/or buying camcorders....brain off....shoooooot!! lol
 
Sorry, *I* would only shoot 4K on the GH4 and therefore those are the relevant crop factors *for me*. YMMV.

(also, I calculate my crop factors with horizontal axis only, so for me the GH4 is 2.34x crop in 4096 and 2.50x in 3840)
 
Besides, all these crop factors exemplified here are when comparing to 35FF which is a still picture standard, and not super 35mm motion picture standard. That makes it all irrelevant to me.
When using the speedbooster with a micro 4/3's sensor you get the field of view close to that of a super 35mm motion picture camera. In 4K mode a tiny bit less...
 
My bmcc speedbooster leaves that little scratch too. Honestly don't care. Turned off the mechanical shutter for safety and it looks superb. Well worth it over my .71 speedbooster. If the .58 covers the whole frame I'd buy it too. and extra 1/3 stop for all my lenses would cost alot more than the $450 for another speedbooster.
 
I slapped on my BMPCC SB again last night and it works great - I don't care about the scratch at all but it does push that shutter housing in a little bit - as that plane is flexible, not sure if that is even a big deal if you will be using e-shutter anyway. But I definitely won't be leaving it on when I'm not shooting with it. Feeling a lot better as that 2.3x crop factor in 4K was starting to bug me a little bit.
 
If it's just the tip of the metal housing just slightly contacting the shutter housing, could you possibly disassemble the SpeedBooster, file the housing down a little, and reassemble everything? I haven't seen a SB in person yet so I'm not sure if this is actually possible.
 
The BMPCC SB has a deeper rear glass element than the BMCC version - and the steel extrudes just passed the glass by a very minimal depth.
 
aldolega said:
If it's just the tip of the metal housing just slightly contacting the shutter housing, could you possibly disassemble the SpeedBooster, file the housing down a little, and reassemble everything? I haven't seen a SB in person yet so I'm not sure if this is actually possible.
Click to expand...
In case anybody is feeling brave, that would be something similar to this.
 
Samuel H said:
Sorry, *I* would only shoot 4K on the GH4 and therefore those are the relevant crop factors *for me*. YMMV.

(also, I calculate my crop factors with horizontal axis only, so for me the GH4 is 2.34x crop in 4096 and 2.50x in 3840)
Click to expand...

What are your full calculations

I get 24p at 2.25 and 30p at 2.4 approx.
 
Taken from personal view, this made sense to me:

4K crop calculations:

Stills horizontal resolution - 4608
Cinema 4K horizontal resolution - 4096
4K horizontal resolution - 3840
This makes crop:

  • Cinema 4K - 1,125x
  • 4K - 1,2x
 
last_SHIFT said:
I slapped on my BMPCC SB again last night and it works great - I don't care about the scratch at all but it does push that shutter housing in a little bit - as that plane is flexible, not sure if that is even a big deal if you will be using e-shutter anyway. But I definitely won't be leaving it on when I'm not shooting with it. Feeling a lot better as that 2.3x crop factor in 4K was starting to bug me a little bit.
Click to expand...

So BMCC SB does work but leaves a scratch. No dispute.

What's confusing is the BMPCC SB. You and this guy here (https://vimeo.com/93428773) have reported it as fitting the GH4, but Andrew @ EOSHD says "The BMPCC will never work on the GH4. The shutter shield and shutter itself is in the way. The best I can do is to screw back the BMPCC Speed Booster glass in the housing so that it doesn't get so close to the sensor, but that means no infinity... best I could do was around 2m." http://www.eoshd.com/comments/topic...-give-128x-crop-almost-full-frame-look/page-3

From photos the BMPCC SB's rear element sticks out further than the BMCC SB's, but it doesn't seem to have any extra structure around the narrow rear element over the BMCC SB. I'm assuming the BMPCC SB's rear element is narrow enough to fit through the sensor housing, or am I wrong? But obviously I don't think Andrew has been lying. What's the deal?
 
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DerekPW said:
What are your full calculations

I get 24p at 2.25 and 30p at 2.4 approx.
Click to expand...

I already posted them a couple of pages back, I'll add some minor details here:

* the sensor is 17.3mm wide, which means a 2.08x crop factor (36/17.3) (I always use the horizontal measure only; it doesn't make sense to recalculate the crop factor if I crop the image vertically, say, for a 2.35:1 finish)
* the sensor is 4608 pixels wide, which means 2.34x crop factor shooting 4096 (2.08*4608/4096) and 2.50x crop factor shooting 3840 (2.08*4608/3840)
* the standard speedbooster is 0.71x which makes those crop factors 1.66x (2.34*0.71) and 1.77x (2.50*0.71)
* the BMCC speedbooster is 0.64x which makes those crop factors 1.50x (2.34*0.64) and 1.60x (2.50*0.64)
 
Guys, any help with confirming that the BMPCC SB indeed fits? (Don't care about cosmetic scratches on the sensor housing and even am willing to file stuff away.) If it's simply the case that the sensor housing physically blocks the protruding rear element of the BMPCC SB (i.e. that people have been mistakenly calling their "BMPCC SB's" "BMCC SB's"), it should be immediately obvious... The conflicting reports are confusing.

I'm waiting on this to pull the trigger on the BMPCC SB or BMCC SB for Leica R that Metabones just released. Thanks.
 
Samuel H said:
In case anybody is feeling brave, that would be something similar to this.
Click to expand...

I enjoyed Bloom's GH4 video in which he used the BMCC adapter...

https://vimeo.com/95232892

He also recommended shooting stills without the mirror (or silent mode). That's two notable photographers who are using the adapter without incident.

I'm curious, when or if a GH4 adapter is available... I wonder if the new adapter would be as magnified as the BMCC. In other words, if the BMCC adapter is as close to the chip as Reid and Bloom have warned, would Metabones take that much risk in duplicating? Wouldn't it make more sense for Metabones to have good magnification (that is also ideal for shooting stills with the GH4), yet not as much as the BMCC currently has. I'm not sure if my post is making sense, I apologize. I just think that the BMCC might possibly be "as good as it will ever get" unless you make VERY brave modifications as mentioned earlier.
 
aly324 said:
Guys, any help with confirming that the BMPCC SB indeed fits? (Don't care about cosmetic scratches on the sensor housing and even am willing to file stuff away.) If it's simply the case that the sensor housing physically blocks the protruding rear element of the BMPCC SB (i.e. that people have been mistakenly calling their "BMPCC SB's" "BMCC SB's"), it should be immediately obvious... The conflicting reports are confusing.

I'm waiting on this to pull the trigger on the BMPCC SB or BMCC SB for Leica R that Metabones just released. Thanks.
Click to expand...

Anyone? Please?
 
I'm looking at purchasing another Metabones Speedbooster for my second GH4 body. I'm trying to decide between the regular MFT version, the BMCC version, and the BMPCC version.

Ryan Lightbourn said:
Just to update...the BMCC Speedbooster will potentially put a permanent scratch on the shutter housing which sits a few mm's above the sensor (see attachment). It's good to know that it's unlikely for the SB rear glass to hit the sensor though.

To be honest, I'll probably keep on using this one instead of forking over $400 for the MFT version. Especially since it's compatible with my BMCC & BMPCC.
Click to expand...

Ryan, can you please update us on your experience with the Metabones Speedbooster BMCC on your GH4. How often do you use them together? Has the scratch on the sensor frame gotten more pronounced with repeated use? Has it interfered with the camera's operation at all?

plasmasmp said:
My bmcc speedbooster leaves that little scratch too. Honestly don't care. Turned off the mechanical shutter for safety and it looks superb. Well worth it over my .71 speedbooster. If the .58 covers the whole frame I'd buy it too. and extra 1/3 stop for all my lenses would cost alot more than the $450 for another speedbooster.
Click to expand...

Plasmasmp, could you please update us on your experience with the MBSB BMCC + GH4 as well? Same questions as above?

last_SHIFT said:
I slapped on my BMPCC SB again last night and it works great - I don't care about the scratch at all but it does push that shutter housing in a little bit - as that plane is flexible, not sure if that is even a big deal if you will be using e-shutter anyway. But I definitely won't be leaving it on when I'm not shooting with it. Feeling a lot better as that 2.3x crop factor in 4K was starting to bug me a little bit.
Click to expand...

Last_SHIFT, could you please update us on your experience with the MB SB BMPCC + GH4. I would expect that Speedbooster version to cause more damage to the GH4 sensor frame than the BMCC version since it protrudes further.
 
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