Meet the Forbes 70 - an IMAX 70mm motion picture camera prototype

[richg101]

 

Still yet to shoot anything of worth, but here is another 'worst case scenario' type sample.  Pulled up the raw by at least 2 stops due to the light levels.  Surprised how well the pocket raw files stand up to being ragged

[JESEOS CHRIST]

I'd like to see this designed with the image originating from an APS or full frame sensor.

[noone]

I'd like to see this designed with the image originating from an APS or full frame sensor.

Would be interesting.

 

Very clever idea and build.

 

makes me want to experiment and try an extremely poor mans version using a Polaroid 600SE and bits of cardboard.     Need a cheap glass focusing screen back first though.

[Jason Nower]

I use to work with DOF adapters on Ground Glass for a long time with the first JAG 35 adapters for the HV20. They are ok but they have their problems (namely dust and the look of ground glass), what I think would be extremely impressive is if MetaBones can make an optical adapter for the full frame (5d Mark iii) to pump to 65mm (or somewhere close).

 

reasons: Full Frame has less pixel density and I personal find it's image to have a greater tonality not just DOF. Also, less of a leap in terms of format jumping.

 

Everything that I have see from MetaBones has been, in my humble opinion, the way to go. 

 

that said, this is a great step forward and shows where we should be heading and MAJOR CONGRATS to RichG101. Great build!!

[richg101]

Thanks for all the kind suggestions chaps.  As it happens, around 8-9 months ago i was in discussion with a colleague about development of a focal reducer for full frame to medium format.  Unfortunately in order to obtain adequate quality the optics would have to be large and therefore need to be seated very deep within the mirror box of the 5dmk3- to the point where the camera would need mirror removal to obtain enough room.  At the time there were no mirrorless full frame cameras released.  Now the a7 range is so strong I feel the development is possibly worth the investment of time, but not by me.  As sensor resolutions go up, it becomes increasingly harder to create lenses that will resolve suitable lp/mm's and therefore a very high quality focal reducer that can compress the massive resolving power of zeiss and Schneider medium format lenses into a smaller area is something that will indeed be a viable commercial product.  However, it should be noted that it is only the resolving power that one would obtain from these lenses in this instance.  the actual aesthetic of the larger format wont be duplicated by focal reduction onto a smaller sensor.  Also, the increase in lens speed is also less of a jump compared to existinf aps-c-full frame focal reducers due to the fact that in f-stop terms the medium format lenses tend to be f2.8 or slower, with only a handful being any faster.

[richg101]

[jgharding]

I'm unendingly impressed by the fact you've built such a wonderful thing yourself! Congratulation! the footage causes joy

[Nikkor]

However, it should be noted that it is only the resolving power that one would obtain from these lenses in this instance.  the actual aesthetic of the larger format wont be duplicated by focal reduction onto a smaller sensor.

 

Any bases on this assumption? Because I have observed that a focal reducer may introduce some aberrations but the looks stay the same. Actually the reason behind the looks doesn't change. 

If anybody has troubles believing this, he can take a FF DSLR and for example a 135 @2.8 and do the Brenzier method with a 2x2 stich (4images), there you have your medium format. The looks are not some mystirious properties, they just come from long loneses with big image circles, a focal reducer compresses the image, it doesn't mystiriously/substancially change the dof behaviour.

[richg101]

I'm unendingly impressed by the fact you've built such a wonderful thing yourself! Congratulation! the footage causes joy

 

thanks man:)

 

 

Any bases on this assumption? Because I have observed that a focal reducer may introduce some aberrations but the looks stay the same. Actually the reason behind the looks doesn't change. 

If anybody has troubles believing this, he can take a FF DSLR and for example a 135 @2.8 and do the Brenzier method with a 2x2 stich (4images), there you have your medium format. The looks are not some mystirious properties, they just come from long loneses with big image circles, a focal reducer compresses the image, it doesn't mystiriously/substancially change the dof behaviour.

 

It's beyond my vocabulary and knowledge of physics to explain why I feel focal reducers don'y quite deliver the same step gradation between in and out of focus areas.  I would probably trace my reasoning back to the fact that a focal reducer shortens the focal length and therefore the lens is no longer as 'long'.  We're now comparing short and fast lenses vs long and slow lenses.  

 

I think the shot at 00"12 on the video above (40mm f4), from around 1.5 mtrs away shows the way the bloke with the camera pings out at you.  It's definitely a sensor size issue that is creating this look.

 

I really hope I'm wrong because if the A7s were coupled with a good reducer and hassy lenses, and this look were obtained, Forbes will remain indoors as a display item from then on!:) 

[Nikkor]

I don't think it will invalid the forbes because you can always put 5x4 lenses inside them. If you don't want to make the groundglass bigger you can put a focalreducer inside it.

 

The focal length reduction is not really reducing focal length in the way you are saying, the design is not the same as a zoom lens.

It changes the light angle behind the lens with an already formed real image and therefore the focal distance becomes shorter -> you can measure this and the focal length obviously will be reduced to the same degree as the view angle gets bigger, but the whole system of the lens in front of the focal reducer still works the same. A tele zoom for example, doesn't use the whole system, as you zoom out,the light rays that create an image will start to use less of the front elements and create "a different lens".

 

Oh, I almost forgot, I think I might have found another way to get the effect, without focal reducers nor medium format lenses. If I find some time I will check the theory on it ^^' It might be the "secret" of some zeiss lenses.

[Rudolf]

Rich, this is totally astonishing. You are gifted with very much talent!

I lost much of my interest for digital cameras during the last year (and I don't understand anything about the technical background) but this...

man thats epic! 

 

[richg101]

Thanks Rudolf:)  Glad you like it man.  

 

 

 

Just testing two different 80mm lenses.  (80mm is a 'normal' lens on the Forbes 70)