Achieving full 6x4.5 format with Hasselblad CFV digital backs

[marco_ristuccia]

<p>Hi all,<br /> recently I happened upon some lens adapters called "speed booster" made by Metabones.<br /> Those special adapters use a special lens group that optically compress (adapt) the full format into the APS-C one.<br /> The result is that we can use a full-frame lens mounted on a mirrorless camera without loosing its full angle of view. They also sponsor a 1 stop light gain and better MTF.<br /> Just thinking that creating such an adapter for Zeiss/Hasselblad lenses when used with a CFV back could be much more affordable than producing a full-frame MF sensor. This way we could use the full FOV of the Hasselblad lenses with, let's say, a CFV-50c.<br /> What do you think? Would a Kickstarter project for producing this kind of adapter have success? For, let's say, a price target of $1000,00 - $1500,00?<br /> Best,<br /> Marco</p>

[Ed_Ingold]

<p>The rectangular format CFV backs, 35 MP and 50 MP, have a cropping factor of 1.1 compared to a full 4.5x6 cm. My shorts are not in a knot over that. Even the 1.5x cropping factor of the square 16 MP version is no big deal.</p>

<p>Putting a cheap (relatively) piece of glass between those Zeiss lenses and the focal plane is definitely a big deal. I'm reluctant to use filters in front of the lens, much less behind it where the effect is multiplied.</p>

<p>I don't think "full frame" MF sensors are going to happen any time soon. The expense of producing sensors is exponentially proportional to the area, and the infrastructure needed to support the sensor would be crowded on the backside. Other than the challenge of obtaining wide-angle results, there are few downsides to a cropping sensor. I had to buy a 40mm lens, which was otherwise at the long end of the list.</p>

[marco_ristuccia]

<p>Unfortunately the CFV-50c CMOS sensor has a cropping factor of 1.3 in respect to a Hassy 645.<br /> I already have a 40mm but often I feel it is not wide enough when used with this digital back.<br /> I agree with you that putting a glass between the lens and the camera could be very risky in terms of IQ. But according to reviews Metabones' speed booster ultra adapters (to name one, there are other similar solutions from other companies) maintain a very high image IQ (comparable to the original one), and even sponsor a 1-stop light gain which could be very useful with MF lenses that are not so fast.<br /> So theoretically it could be possible to achieve a 60x45 to 44x33 (CFV-50c) conversion, and even a 60x60 to 33x33 conversion to have a full square format with the original lens's FOV.<br /> Regarding the sensor size, indeed that was my idea. Producing full 6x4.5 or 6x6 sensors is very difficult and expensive. Then why not seeing the problem the other way around? Why not "simply" adapting lenses' coverage to the sensor?</p>

[ondebanks]

<p>Marco,</p>

<p>You mentioned that the SpeedBooster and similar devices are for mirrorless cameras, but I don't think you have thought through all the implications of that.</p>

<p>They can <em>only</em> work on mirrorless cameras - the adapter requires the space saved, by not having a mirror-box, to accomodate its own optical path and the focal reduction effect. So it is not enough to design a medium format SpeedBooster adapter; you also have to design an accompanying <em>camera</em> between the adapter and the back.</p>

<p>Hasselblad do have a mirrorless camera body now, but it does not take detachable backs.</p>

<p>The other issue is that all the existing SpeedBooster type devices are for cameras with focal plane shutters. It would be take a very high level of engineering for a 3rd party to develop a SpeedBooster which can actuate the leaf shutter on the Hasselblad lens in front of it.</p>

<p>Sorry to play devil's advocate - I do like the idea, notwithstanding. For some time, I've pondered the choice between a SpeedBooster + Fuji X-T series camera, vs. a full-frame Nikon. Both have nicer interfaces and more modern sensors than my full-frame Canon. </p>

[Ed_Ingold]

<p>There was an Hasselblad shift adapter with a reverse tele lens for use with 200/500 bodies. As long as the adapter doesn't intrude into the body, it would work on any camera.</p>

<p>It is also possible to make inverted telephoto, rectilinear lenses with an effective focal length shorter than 40 mm. However they would be very large, as witnessed comparing the CF40 with a CF50, etc. The mirrorless X1D will have a 30 mm lens, which is a start in the right direction.</p>