GH5 Speedboosted EF glass with IBIS

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filmguy123

Veteran
I was under the impression I would need to manually figure out my focal lengths for speedboosted glass via some math. However, I got the newest (gen 5, positive EF locking) metabones speedbooster (.71x EF to m43) for the GH5. I have Zeiss Milvus EF glass.

It seems the electronics are auto-reading the focal length through the active EF speedboosted mount. So, I can select IBIS on, but I cannot manually dial in my focal length.

Any concern here? Or do the electronics in the metabones do the math automatically, and will they pass the properly converted focal length to the GH5? My concern is that a Milvus 35mm is being read as a 35mm for IBIS instead of a "24.85" lens (speedboosted focal length).
 
One can notice the IBIS not working properly very clearly without the correct focal length set...I use it with a Metabones XL Nikon mount and Nikon zooms and it's immediately apparent when you select another focal length without adjusting the camera manually...(not talking about zooming while filming, for which I would dolly instead).
 
Different question but I'll keep it in here:

Does the smart adapter also adjust for the exposure / f-stop?

I am a bit confused, because I put on my Milvus 28mm f/2.8 and it showed as f/2.0 when all the way open. Cool, it adjusts for making the lens a stop faster, I thought.

But then I put on my Milvus 1.4 glass, and full open, it merely shows 1.4. I am assuming the glass is still a stop faster due to the reducer... but... why the inconsistency in how that is displayed electronically?

Milvus 28 f/2.8 showed as 2 all the way open, but my Milvus 35 and 50 (1.4 lenses each) showed as same 1.4 all the way open...
 
Just guessing, but probably because there are no electronic f/1 lenses out there (1 stop difference from f/1.4), and the camera is not programmed to show that (f/1.2 being the limit).
 
That's a good guess.. hmm.. so how would it portray that then as you count up? If f1/.4 = f/1.0, then i click a few notches up to f/2.0... what's f/2.0?

True 2, or 1.4?
 
Pretty sure that was always the issue with f1/4 electronic glass on the Speedbooster. It can't read an accurate value below f1.4 or something like that.

A 1 stop focal reducer is always 1 stop brighter no matter what the camera is telling you it is. The camera doesn't make it darker or brighter but it can't report the value on screen accurately. You are at f1.0 but the camera can't display that. Maybe the electronics do better as you step down the lens. Not sure as most of the lenses I have tried with a SB were Rokinons or f2.8 Canon zooms. I have never tried an electronic f1.4 lens before.
 
filmguy123 said:
That's a good guess.. hmm.. so how would it portray that then as you count up? If f1/.4 = f/1.0, then i click a few notches up to f/2.0... what's f/2.0?

True 2, or 1.4?
Click to expand...

I don't know too much about SpeedBoosters, I don't use them TBH.

But I think (and I say this kindly) you're being struck with a little 'paralysis by analysis' with everything, lol. [Been there, done that.]

The lens weight, the SB #s, the FF lens quality, etc...it's of course beneficial to know your equipment and how things works, but sometimes you have to let things go and just shoot.

You'll learn that one lens mount will be fine after much wear and tear and another one from a different company may not be with the same lenses. Or you'll see and feel the torque your lenses are producing and make a gut decision that certain ones are too heavy.

Or that it doesn't matter what the numbers say from the SBs. If you'll need more light, you'll add more light. If you need to match a shot based on DOF, you'll stop up/down or move in/out.

And top-of-the-line MFT lenses are really nice and if you take a look at some of Jon Pais' videos (who responded in your other thread) on YT, he has some great samples that are high-quality and look super "clean" IMO. (I love the Voigtlanders for many reasons, but it's also possible those Panasonic Leicas are of higher resolution.)
 
Sure, sure, lots of new gear to figure out and don't want to break anything or know if I'm missing anything :) I hear ya.

I was also under the impression that the electronics would just read the actual lens settings ie 1.4 = 1.4, 2.8 = 2.8, 4 = 4, etc. -- and I would be in on the secret that it's all a stop faster.

It has def. thrown me for a loop to have an inconsistency there. So now I can assume on my f/2.8 lens that I am getting an actual f-stop reading that is accurate (where f/2.8 is displaying as f/2, thanks to the speedboost) but I have no idea where it transitions on my f/1.4 glass. Really annoying with multiple lenses and trying to work fast to not know when f/2.8 is f/2.8...
 
filmguy123 said:
Sure, sure, lots of new gear to figure out and don't want to break anything or know if I'm missing anything :) I hear ya.

I was also under the impression that the electronics would just read the actual lens settings ie 1.4 = 1.4, 2.8 = 2.8, 4 = 4, etc. -- and I would be in on the secret that it's all a stop faster.

It has def. thrown me for a loop to have an inconsistency there. So now I can assume on my f/2.8 lens that I am getting an actual f-stop reading that is accurate (where f/2.8 is displaying as f/2, thanks to the speedboost) but I have no idea where it transitions on my f/1.4 glass. Really annoying with multiple lenses and trying to work fast to not know when f/2.8 is f/2.8...
Click to expand...

Does it really matter?
 
It matters is you are on the fence about a buying decision. What if the speed booster stopped down the lens to the maximum opening it can report in the view finder? Then you would not be getting all the light the lens could potentially offer.
 
Don’t know that Panasonic has stated the weight limits of the GH5 lens mount. Pretty sure the AF100’s was 2 lbs, but that was a different camera, & era.

In addition to the weight of the lens take in to account it’s form factor too. A physical longer lens is going impart more leverage on the mount than a shorter lens that weighs the same, especially if it gets banged, or your using a hand on the lens to support the camera.

I have .71x SpeedBoosters, & a dozen EF lenses, but rarely use them on my GH5, or FS7. My issue with SpeedBoosters is they sometimes don’t preform optimally in backlight, especially if there are specular highlights, &/or flare. I do continue to use the EF glass on the FS7 with a Metabone’s Smart Adapter, but mostly rely on native m4/3 lenses on the GH5.
 
Answer: For my f/1.4 speedboosted lenses, the pre-boost aperture is displayed consistently for the entire lens. Do the math in your head!

For my f/2.8 lenses, the boosted aperture speed is displayed. Don't do any math.

More info...

Here is the official scoop:

For use with fast lenses (faster than f/1.8), the pre-boost apertures will be displayed in the camera.

Slow lenses will report boosted apertures to the camera body but fast lenses will report pre-boost apertures. We won't show f/0.7 with a f/1.2 lens attached, but show f/1.2 instead.

Example:

a) EF 85/1.2L attached, camera display = f/1.2, physical aperture (lens + Speed Booster combined) = f/0.74.
b) Sigma 18-35/1.8 attached, camera display = f/1.0, physical aperture (lens + Speed Booster combined) = f/1.0.

WHY / EXPLANATION (found posted on another forum)

Many MFT cameras do not recognize sub-f/1.0 apertures, so pre-boost apertures are reported in EXIF when you attach a lens which would drop below f/1.0 (e.g. f/1.2 => f/0.9 as in the case of EF50/1.2L USM). The MFT committee might simply have not thought of it as likely in 2008 (and the same for its predecessor, Four Thirds System of 2003).

You know what, the EXIF standard itself does not support any aperture numerically lower than f/1.0, so it is not even MFT to blame here. In EXIF, ApertureValue is an unsigned rational number which is the power of root 2. e.g. sqrt(2)^0 = f/1.0, sqrt(2)^1 = f/1.4, sqrt(2)^2 = f/2, sqrt(2)^3 = f/2.8, and so on. Since by definition this field is unsigned, we can't use -1 to represent f/0.7 for example.

Sub-f/1.0 apertures did not become commonplace until Dr Brian Caldwell and Wilfried Bittner came along and did their magic in 2013. The rest of course is history.
 
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