upside down

[Olivier]

Out of the pool, little B realized that she was wearing her googles upside down. This, of course, had to be remembered.

X-T1 with Nikkor 105 2.5 AIS + lens turbo 2.

[Fons Baerken]

good image to keep for future stories

[Frank Fremerey]

great model interaction!

[Bill Mellen]

Very nice composition with the angle of the fingers and upside down goggles.

You will treasure this one!

[Gary]

I've looked at this image a number of times and it always brings a smile to my face.

[armando_m]

did she actually went swiming with googles upside down ?

thanks for sharing

[elsa hoffmann]

That is a great portrait.

[Erik Lund]

Really cute! I really like the rendering and framing, perfect

Again the 105mm 2.5 nails it... and this time on Fuji

BTW, obviously  the Lens Turbo II does a good job here apparently... Not sure I like the idea of copying the Speedboster though...

[Olivier]

Thanks everyone, and don't hesitate to critisize of course.
Armando: she was swimming in her tiny pol, it is hard to immerse your head fully in it so I am not sure it really matters how you wear your googles...
Erik: I am pleased with what I get from the 105 on the X-T1, especially with the focal reducer which makes it more "natural" for portraits. I have not considered optical qualities very seriously and it is possible that corner sharpness could be regarded as disappointing by some, but I don't really care, especially for portraits.
A quick comparizon (with and without Lens Turbo 2) with the Nikkor 50mm 1.4 AFD indicates a much better performance wide open with the lens turbo: more contrast, less haze, more apparent sharpness. I am not considering color attributes or potential issues (fringing...) as I don't see them anyway, being colorblind.
I don't know if the Lens Turbo is really a copy of the Speedbooster. Does it violate any patent? It would be a shame if it did. But focal reducer have been around for a long time, especially in astronomy so the concept is not really new.
Olivier

[Erik Lund]

From the Metabones site:

Mounted between a mirrorless camera and a SLR lens, Speed Booster® increases maximum aperture by 1 stop (hence its name), increases MTF and makes lens wider by a factor of 0.71x. Optics designed by Caldwell Photographic in the USA (patent pending).


They are actually a little too modest since the patent has been issued, Caldwell Photographic holds a couple of US patents on this technology, and Applications in China.




Optical attachment for reducing the focal length of an objective lens

Abstract(US8879901)
An optical attachment configured to be operably attached to the image side of an objective lens to reduce the focal length and focal ratio of the objective lens. The focal-reducing attachment includes four lens elements and has a magnification of between 0.5 and 1. The focal-reducing lens can work with objective lenses having relatively large working distances for a large format size as well as with cameras having a smaller format size and relatively small permissible working distance.

Claim 1 and 2:

What is claimed is:
1. A focal reducing attachment for use with an objective lens and having in order from an object side to an image side: a first lens element having a first negative power and an object-side concave surface;
a second lens element having a first positive power and an object-side surface having a curvature CvOb2;
a third lens element having a second negative power greater than the first negative power and having an image-side surface having a curvature CvIm3;
a fourth lens element having a second positive power and an image-side surface; and
wherein the focal reducing attachment has an overall power phi such that (CvOb2+CvIm3)/phi >3 and an overall magnification M such that 0.5 <= M <= 1.
 
2. A focal reducing attachment according to claim 1, in which the combined focal reducing attachment and objective lens defines an f-number of 0.68 or greater.
 

I have not gone into exactly how the glass elements are designed in the Lens Turbo so it could very well be that Lens turbo is different on some points to make it 'not equal' to the Speed Booster design...
A full freedom to operate analysis is needed for that

[Olivier]

Thank you for the quite detailed information, Erik.
I konw by experience that a FTO analysis is not all black or white, the patent agent my company works with will never sign with his bload or even give a clear and written statement!
This afternoon I had a long meeting with a customer about competitor's patents susceptible to block the launch of our new technology. It was really interesting to see how we found ways around patents that were clearly prior art...
At one point I even wondered if filing patents was really the right thing to do in order to protect an invention. maybe keeping it secret is more efficient!
Anyway, i am happy with the Lens Turbo 2.

[Erik Lund]

Consulting in Patents and freedom to operate is now my main income besides photography
Very interesting business but some times parts of the organization don't want to listen or doesn't understand that things are not black or white with intellectual property