Internal stabilization, non-electronic lenses, and speed boosters

[tomsemiterrific]

I note we have a growing array of cameras with internal stabilization---offering stabilization even with non-electronic lenses--like FD lenses, or Rokinon lenses, etc.

When these cameras allow shooting with this non-electronic lenses the camera's stabilization asks a simple and reasonable question: "what are you?" And the lens, vis a vis the videographer, responds, "I'm a 35mm lens, or an 85mm lens, or a ...whatever."

And the camera responds accordingly, the shooter shoots, and the rest is history.

I promise I'm getting to my question---but I have to make one more observation: when such a non-electronic lens is coupled to the camera with a speed booster it is no longer functioning as what it originally was: a 35mm lens or 85, or 135mm lens,  whatever. Right?

Now, here's my question---does the internally stabilized camera "know" the lens is coupled by a speed booster and adjusts internally accordingly? Or does it not know and the stabilization is negatively affected? Or, does it make no difference in regard to the stabilization?

Hmmmm....I'm sorry. I think that's three questions.

Why am I asking this?

It's simple:

I'm asking this because non-electronic lenses, in my admittedly limited experience, do not seem as stable when mounted with a speed booster as they are when they are simply mounted with a simple mount to an internally stabilized camera.

I guess a final question might be, "Am I wrong about this perception or is this a consideration that needs to be....well, uh,...considered? Would love to have the best stabilization possible with non-electronic, speed booster mounted lenses! 

[aldolega]

The IBIS software needs to know the correct angle of view to work properly. But since AOV isn't labeled on lenses, it asks for the focal length. Obviously the IBIS software knows the camera's sensor size, so once it has the focal length it can then calculate the AOV, and then it knows how large or small to make its corrections.

So you would enter the effective focal length of the lens + booster, as a combination, into the camera. So if you have a .71x booster, and a 50mm lens, you would enter 35mm. For a 100mm lens with a .64x booster, you would enter 64mm (or whatever the closest option the camera gives you).

If the lens is "dumb"- meaning it has no electronics transmitting EXIF information (i.e. the lens' focal length, aperture, etc)- the camera will have no idea what length it is, regardless of whether your booster/adapter is electronic or not.

Now, if you mount a smart lens on a smart speedbooster, I would hope that the speedbooster's firmware would apply the booster's reduction power (.71x or .64x or whatever) to the focal length before sending it to the camera. I have no idea if this is done, but if not it certainly should be. I would think Metabones, of all the booster/adapter companies, would be the most likely to have implemented this.

Your experience with differing stabilization when mounting dumb lenses via booster vs. plain adapter probably just has to do with the camera having the wrong focal length entered for one or the other (assuming you used the same value for both).

[tomsemiterrific]

Thanks for such a helpful and clearly stated reply. I'm glad to know I am right about this and the stabilization issue was not just my imagination. I wonder if that's the same case with those voices I hear I keep hearing?

[tomsemiterrific]

10 hours ago, aldolega said:

The IBIS software needs to know the correct angle of view to work properly. But since AOV isn't labeled on lenses, it asks for the focal length. Obviously the IBIS software knows the camera's sensor size, so once it has the focal length it can then calculate the AOV, and then it knows how large or small to make its corrections.

So you would enter the effective focal length of the lens + booster, as a combination, into the camera. So if you have a .71x booster, and a 50mm lens, you would enter 35mm. For a 100mm lens with a .64x booster, you would enter 64mm (or whatever the closest option the camera gives you).

If the lens is "dumb"- meaning it has no electronics transmitting EXIF information (i.e. the lens' focal length, aperture, etc)- the camera will have no idea what length it is, regardless of whether your booster/adapter is electronic or not.

Now, if you mount a smart lens on a smart speedbooster, I would hope that the speedbooster's firmware would apply the booster's reduction power (.71x or .64x or whatever) to the focal length before sending it to the camera. I have no idea if this is done, but if not it certainly should be. I would think Metabones, of all the booster/adapter companies, would be the most likely to have implemented this.

Your experience with differing stabilization when mounting dumb lenses via booster vs. plain adapter probably just has to do with the camera having the wrong focal length entered for one or the other (assuming you used the same value for both).

I kept thinking about this and decided to look up the description of the speed booster from the seller. Here's what he wrote:
In common lens adapters, cropping effect occurs in all APS-C digital cameras with 1.5x magnification. This adapter reduces focal length to 0.72x , to adjust the image size to near 1:1 so that the focal length of the image is close to actual focal length of the lens, e.g. 50mm x 1.5 x 0.72 = 54mm. 
If this is correct then a 100 mm lens with a 0.72 focal reducer on an aps-c sensor would come out as follows: 100mm X 1.5X 0.72=108. Basically providing you with a full-frame angle of view.

So, factoring in the crop sensor into the equation what do you tell the camera? 70mm, or 100?
 

[Nikkor]

4 minutes ago, tomsemiterrific said:

I kept thinking about this and decided to look up the description of the speed booster from the seller. Here's what he wrote:
In common lens adapters, cropping effect occurs in all APS-C digital cameras with 1.5x magnification. This adapter reduces focal length to 0.72x , to adjust the image size to near 1:1 so that the focal length of the image is close to actual focal length of the lens, e.g. 50mm x 1.5 x 0.72 = 54mm. 
If this is correct then a 100 mm lens with a 0.72 focal reducer on an aps-c sensor would come out as follows: 100mm X 1.5X 0.72=108. Basically providing you with a full-frame angle of view.

So, factoring in the crop sensor into the equation what do you tell the camera? 70mm, or 100?
 

The camera is asking for the focal length, so the answer is no. The speedbooster shortens the focal length, the sensor doesn't change the focal length at all.

[Chrad]

You'd tell the camera 72mm.

[tomsemiterrific]

33 minutes ago, Nikkor said:

The camera is asking for the focal length, so the answer is no. The speedbooster shortens the focal length, the sensor doesn't change the focal length at all.

I don't understand the answer "no." What I was asking was this in regard to a 100 mm lens mounted with a .72 focal reducer on a crop sensor: "So, factoring in the crop sensor into the equation what do you tell the camera? 70mm, or 100?"

[Nikkor]

6 minutes ago, tomsemiterrific said:

I don't understand the answer "no." What I was asking was this in regard to a 100 mm lens mounted with a .72 focal reducer on a crop sensor: "So, factoring in the crop sensor into the equation what do you tell the camera? 70mm, or 100?"

You don't factor in the crop sensor.

[aldolega]

How the AOV compares to a full-frame camera is completely irrelevant.

You tell the camera the focal length of the lens + booster, that's it. As I stated above. 100mm lens X .72x booster = 72mm.

[noone]

You are not changing the camera by adding a focal reducer, you are changing the lens.

If you use a dumb focal reducer (like a Lens Turbo), then you would tell it the focal length AFTER the reduction but you do not take into account the 2x crop (the camera does that).

If you are using a smart adapter/focal reducer with a "smart" lens (IE with communication between camera and lens) you do not need to tell the camera anything as it "knows" what is mounted (some might not know what the actual lens is but even the stupidest smart adapters seem to know the focal length).      At least that is my experience with IBIS and many adapters from a few different brands.

The only time this question would arise I think is if you use a smart focal reducer with a dumb lens and I would think for that, the best thing to do is ask the focal reducer makers (or try a few experiments if you have the kit).      Interesting question though and I would like to know the answer too (not that I have a smart focal reducer and dumb lens combination otherwise I would try it and see for myself).