Brian Caldwell

Hi Hans:
Using a good diopter will definitely improve the closeup image performance of a single-focus attachment, since it allows the attachment itself to be used closer to its "zero aberration" infinity setting.  I'm not entirely sure what you are describing about the highlight blob ghosting effect.  Most single focus attachments use a plano-concave moving front element followed by a convex-plano stationary element.  The concave surface of the front element is normally very close in radius to the convex surface of the stationary element, and this could set up a pair of reflections that might cause the effect you are seeing.  Its also possible that a reflection from the sensor followed by a reflection from either or both of the plano surfaces can cause noticeable ghosting, although in this case I would expect sharply focused mirror-image type ghosts.  Regardless of the root cause of the ghosting, its appearance can be reduced, but not completely eliminated, by using better AR coatings.

Hi Hans:
Using a good diopter will definitely improve the closeup image performance of a single-focus attachment, since it allows the attachment itself to be used closer to its "zero aberration" infinity setting.  I'm not entirely sure what you are describing about the highlight blob ghosting effect.  Most single focus attachments use a plano-concave moving front element followed by a convex-plano stationary element.  The concave surface of the front element is normally very close in radius to the convex surface of the stationary element, and this could set up a pair of reflections that might cause the effect you are seeing.  Its also possible that a reflection from the sensor followed by a reflection from either or both of the plano surfaces can cause noticeable ghosting, although in this case I would expect sharply focused mirror-image type ghosts.  Regardless of the root cause of the ghosting, its appearance can be reduced, but not completely eliminated, by using better AR coatings.

Awhile back I spent many weeks designing variable diopter systems, including simple 2-element designs using singlets, 4-element designs with achromatic doublets, and a few complex 5 and 6 element designs.  What I discovered was that the limiting aberration in every case was spherical aberration at close focus.  Surprisingly, using more complex designs has very little impact on that spherical aberration, and they have numerous drawbacks including excess cost, and larger size and weight.  It turns out that a simple 2-element variable diopter, such as the ones used in all of the Iscoramas is not such a bad solution at all.  They give fantastic results for distant objects, and only gradually reveal weakness as you focus close.  As an aside, the only thing that I found to reliably eliminate close focus spherical was to allow the elements to get very weak, but this is completely impractical because the elements get huge and the front element motion becomes BIG.
BTW, it doesn't make much sense to talk about f/#'s when evaluating single focus units because absolute pupil size is what really matters.  For example, you might get a terrible result when attaching the unit to a 200mm prime at f/4 because the pupil diameter is 50mm, and yet get a really nice result with a 24mm f/1.4 because the pupil diameter is only 17mm.

The main reason for shooting 1.33x (actually, 1.344x would be best) is to get 2.39:1 output with no waste of a 16:9 sensor.  Shooting 2x on 16:9 and cropping throws away resolution.  Aside from these considerations, there is the aesthetic look that different squeeze ratios provide.  Many people dislike 1.33x because it doesn't look very anamorphic.  However, even 2x anamorphics don't always share the same look.  Rear anamorphics don't look anamorphic at all.  Zeiss 2x Master Anamorphics actually look more like 1.64x true front anamorphics due to their mixed front/rear design.

Its a little complicated due to the fact that the outer surface of the Speed Booster is concave.  But you should have at least 1mm of clearance with this particular combination.  Note for anyone else reading this post that the Speed Booster XL for m43 has more clearance than a Speed Booster Ultra for APS-C.

Its a little complicated due to the fact that the outer surface of the Speed Booster is concave.  But you should have at least 1mm of clearance with this particular combination.  Note for anyone else reading this post that the Speed Booster XL for m43 has more clearance than a Speed Booster Ultra for APS-C.

It depends a lot on the lens.  For some lenses, such as the 50/1.2 Nikkor, there is almost no space between the rear element of the lens and the front element of most  Speed Boosters.  I would hate for you to crush your filter between two lens elements!

A Zeiss Otus plus Speed Booster XL has pretty amazing IQ wide-open at f/0.90 on m43.

A Zeiss Otus plus Speed Booster XL has pretty amazing IQ wide-open at f/0.90 on m43.

Bear in mind that in your case with an 85mm lens the rear of the adapter limits the aperture, so you are shooting at f/2.4 and not f/2.  You would need an Iscorama 42 to shoot at f/2 with an 85mm lens.

Has anyone heard anything about whether the automatic anamorphic crop mode of the GH4 has been retained/improved?  Or will it require manual post-processing?

You're having a paranoid fantasy, Marco.  I design the Speed Booster optics, and my colleague Wilfried designs the mechanical mount.  Together we own the optical design patents and the "Speed Booster" trademark.  That's it - just two people.  We work with subcontractors to manufacture and QC the optical cells, and sell the those cells to Metabones, which itself is just a tiny company.  Any public statement from Metabones about Speed Boosters probably comes from me, so when you say that Metabones is lying you are essentially saying that I am lying.  There is no lying going on here.  I doubt that Samsung - which is a truly enormous company - was even aware of Speed Boosters, much less that its presence or absence played any role at all in their decision to leave the camera business.  No one from Samsung or Sony has *ever* contacted me about Speed Boosters, or anything else for that matter.
Wilfried and I looked at the Samsung NX mount on several occasions, and concluded it was just too much trouble to deal with due to the metal parts surrounding the sensor.  Based on our analysis, it would require several rectangular elements (similar to one of the Lens Turbo designs), which are much more difficult to make and mount accurately.  It would also require a substantial re-design of the Speed Booster optics, which have a unique performance advantage at extremely large apertures (read the patents if you want to understand this).  I personally had big hopes that the NX-mini mount would take off, since that was much more amenable to high quality focal reducer designs with larger reduction ratios - much like the BMCC and BMPCC from BlackMagic.  But unfortunately both NX and NX-mini have both become extinct except for whatever product remains in the marketplace.

At this point, NX accessories are probably best done by NX enthusiasts like Luca.  Otherwise something called "opportunity cost" rears its ugly head.  What it means is that labor and financial resources are limited - especially in small companies - so you have to be very careful about choosing which products to develop.

You're having a paranoid fantasy, Marco.  I design the Speed Booster optics, and my colleague Wilfried designs the mechanical mount.  Together we own the optical design patents and the "Speed Booster" trademark.  That's it - just two people.  We work with subcontractors to manufacture and QC the optical cells, and sell the those cells to Metabones, which itself is just a tiny company.  Any public statement from Metabones about Speed Boosters probably comes from me, so when you say that Metabones is lying you are essentially saying that I am lying.  There is no lying going on here.  I doubt that Samsung - which is a truly enormous company - was even aware of Speed Boosters, much less that its presence or absence played any role at all in their decision to leave the camera business.  No one from Samsung or Sony has *ever* contacted me about Speed Boosters, or anything else for that matter.
Wilfried and I looked at the Samsung NX mount on several occasions, and concluded it was just too much trouble to deal with due to the metal parts surrounding the sensor.  Based on our analysis, it would require several rectangular elements (similar to one of the Lens Turbo designs), which are much more difficult to make and mount accurately.  It would also require a substantial re-design of the Speed Booster optics, which have a unique performance advantage at extremely large apertures (read the patents if you want to understand this).  I personally had big hopes that the NX-mini mount would take off, since that was much more amenable to high quality focal reducer designs with larger reduction ratios - much like the BMCC and BMPCC from BlackMagic.  But unfortunately both NX and NX-mini have both become extinct except for whatever product remains in the marketplace.

You're having a paranoid fantasy, Marco.  I design the Speed Booster optics, and my colleague Wilfried designs the mechanical mount.  Together we own the optical design patents and the "Speed Booster" trademark.  That's it - just two people.  We work with subcontractors to manufacture and QC the optical cells, and sell the those cells to Metabones, which itself is just a tiny company.  Any public statement from Metabones about Speed Boosters probably comes from me, so when you say that Metabones is lying you are essentially saying that I am lying.  There is no lying going on here.  I doubt that Samsung - which is a truly enormous company - was even aware of Speed Boosters, much less that its presence or absence played any role at all in their decision to leave the camera business.  No one from Samsung or Sony has *ever* contacted me about Speed Boosters, or anything else for that matter.
Wilfried and I looked at the Samsung NX mount on several occasions, and concluded it was just too much trouble to deal with due to the metal parts surrounding the sensor.  Based on our analysis, it would require several rectangular elements (similar to one of the Lens Turbo designs), which are much more difficult to make and mount accurately.  It would also require a substantial re-design of the Speed Booster optics, which have a unique performance advantage at extremely large apertures (read the patents if you want to understand this).  I personally had big hopes that the NX-mini mount would take off, since that was much more amenable to high quality focal reducer designs with larger reduction ratios - much like the BMCC and BMPCC from BlackMagic.  But unfortunately both NX and NX-mini have both become extinct except for whatever product remains in the marketplace.

You're having a paranoid fantasy, Marco.  I design the Speed Booster optics, and my colleague Wilfried designs the mechanical mount.  Together we own the optical design patents and the "Speed Booster" trademark.  That's it - just two people.  We work with subcontractors to manufacture and QC the optical cells, and sell the those cells to Metabones, which itself is just a tiny company.  Any public statement from Metabones about Speed Boosters probably comes from me, so when you say that Metabones is lying you are essentially saying that I am lying.  There is no lying going on here.  I doubt that Samsung - which is a truly enormous company - was even aware of Speed Boosters, much less that its presence or absence played any role at all in their decision to leave the camera business.  No one from Samsung or Sony has *ever* contacted me about Speed Boosters, or anything else for that matter.
Wilfried and I looked at the Samsung NX mount on several occasions, and concluded it was just too much trouble to deal with due to the metal parts surrounding the sensor.  Based on our analysis, it would require several rectangular elements (similar to one of the Lens Turbo designs), which are much more difficult to make and mount accurately.  It would also require a substantial re-design of the Speed Booster optics, which have a unique performance advantage at extremely large apertures (read the patents if you want to understand this).  I personally had big hopes that the NX-mini mount would take off, since that was much more amenable to high quality focal reducer designs with larger reduction ratios - much like the BMCC and BMPCC from BlackMagic.  But unfortunately both NX and NX-mini have both become extinct except for whatever product remains in the marketplace.

Stacking two 1.33x anamorphic adapters will result in a 1.77x anamorphic adapter.  This is close to the ideal squeeze of 1.79x that you would want to convert 4:3 to 2.39:1 .  A Speed Booster will shorten the focal length.

Not quite.  You haven't accounted for the huge difference between front and rear anamorphics, both of which have different focal lengths in the horizontal and vertical directions.  I posted the explanation here back in June:  
 

Not quite.  You haven't accounted for the huge difference between front and rear anamorphics, both of which have different focal lengths in the horizontal and vertical directions.  I posted the explanation here back in June:  
 

Thanks Ebrahim.  As always, your contributions here are extremely helpful.  What you are reporting is what I suspected, but its really nice to get confirmation like this since I don't have the camera myself.
FWIW, I am doing research for a product, but its for a system of anamorphic lenses and not a fullframe Speed Booster, which may not be what you were hoping for but which I promise will be very cool.  

Thanks Ebrahim.  As always, your contributions here are extremely helpful.  What you are reporting is what I suspected, but its really nice to get confirmation like this since I don't have the camera myself.
FWIW, I am doing research for a product, but its for a system of anamorphic lenses and not a fullframe Speed Booster, which may not be what you were hoping for but which I promise will be very cool.  

Thanks Ebrahim.  As always, your contributions here are extremely helpful.  What you are reporting is what I suspected, but its really nice to get confirmation like this since I don't have the camera myself.
FWIW, I am doing research for a product, but its for a system of anamorphic lenses and not a fullframe Speed Booster, which may not be what you were hoping for but which I promise will be very cool.  

Thanks in advance if anybody can help me track down the following information.  I need to know the exact dimensions of the 16x9 video frame used by the Sony A7s-II in both 4k and 2k video modes.  All that I'm confident about are the following:
1) full still sensor size measures 35.8mm x 23.9mm
2) full sensor resolution in still mode is 4240 x 2832.
3) 1 and 2 together imply a pixel dimension of approximately 8.44 microns square
4) 4k video resolution is 3840 x 2160.
SO:  does this mean that the rectangle of sensor area used during 4k recording is 32.41mm x 18.23mm? 
Similarly, what would be the as-used sensor dimension when shooting 4k in "full-frame" mode?
 

I agree for the most part, although 1.79x is a good alternative to 2x, since it is more efficient and in a good implementation actually looks more anamorphic than many 2x lenses.

Apologies in advance if this is widely known.  Personally, I've never found a really good explanation of why front anamorphs produce oval bokeh and rear anamorphs don't, despite reading my fair share of patents, technical papers, internet gossip and the like.  Feeling that my own understanding needed some firming up I finally set up some paraxial models and went through the math in gory detail.  It all boils down to how front and rear converters alter (or don't alter) the f/#, and basic DOF type circle of confusion calculations.  It has nothing to do with higher order aberrations, or the shape of the front lens, or various mechanical aspects of the lens.
Briefly:
1) A front anamorph is just a special case of a front afocal attachment, and as a result it preserves the f/# of the lens its attached to.  With an anamorphic front lens the focal length is shorter in the powered axis than in the non-powered axis.  For example, consider a 2:1 anamorph attached to a 100mm f/2 spherical lens.  In this case the net focal length is 50mm in the powered axis and 100mm in the non-powered axis, but in both cases the aperture remains f/2.  If you venture into the weeds to do circle of confusion calculations for a given object-space defocus you discover that a de-focused point source evaluated at the image plane is an ellipse with an aspect ratio of 4:1.  However, you only need to de-squeeze the image by 2x to correct the in-focus geometry, so you are left with de-focused ellipses with an aspect ratio of 2:1.
2) A rear anamorph is just a special case of a rear-mounted teleconverter, and as a result it *does not* preserve the f/# of the lens its attached to.  In particular, in the powered axis the aperture becomes slower.  For example, consider an 50mm f/2 spherical lens with a 2x rear anamorph.  Here the net focal length is 100mm in the powered axis, but the aperture has dropped to f/4, and is still 50mm f/2 in the non-powered axis.  When you do the circle of confusion calculations with object-space defocus you find the on-sensor defocused image to be an ellipse with a 2:1 aspect ratio.  When you desqueeze by 2x this defocus ellipse becomes a perfect circle.
Bottom Line:  Rear anamorphs have circular bokeh because they *don't* preserve the f/# of the spherical lens in both axes, while front anamorphs have elliptical bokeh because they *do* preserve the f/# of the spherical lens in both axes.