Hasselblad digital backs and crop factor

Discussion in 'Medium Format' started by a_petkov, Mar 10, 2006.

  1. Hello,

    I read that the area of the digital sensor in the Hasselblad backs is
    not as large as the film plane. Therefore the captured image is
    cropped 1.5 times(?). So if you shoot with the 50mm lens you get a
    result with an actual focal length of 75mm.

    Is it correct to assume that if you want to capture a digital image
    with the POV of a 50mm Distagon you need to have a 30mm lens?

    I hope my question made some sense.

    Thanks,
    Anastas
     
  2. POV should read Angle of View!
     
  3. Yes, that's how crop factors work. Of course the 30mm lens is a fisheye, which will give quite different results than the 40mm or 50mm lenses. A digital back would not be particularly useful without a 40mm lens in the kit. Hasselblad has a new IF 40mm with automatic FLE, especially for digital. The performance specs are phenomenal, as is the price. If you have to ask, you can't afford one.
     
  4. What the crop factor is will depend on the back being used -- not all are the same size (in terms of HxW of sensor) or resolution. Also: are you comparign to a 6x6cm ( really 54x54mm) format Hasselblad "V" seires camera or a Hasselblad "H" (6x4.5cm) camera? current 22 and 39 Mp sensors use a sensor that is about 39x50 mm in size.
     
  5. Thanks for the answers.
    I checked out the IF lens, out of pure curiousity - it IS quite expensive.

    I was more interested in the V system backs (since I have a 500cm). So the crop factor for the H system is much smaller?

    Best Regards,
     
  6. I was more interested in the V system backs (since I have a 500cm). So the crop factor for the H system is much smaller?
    Let's see: sensor size is fixed at 39x50mm (more or less) for either a V or H seres camera; film format size 6x4.5cm vs. 6x6cm. what do you think?
     
  7. cpj

    cpj

    No. The "crop factor" is not a universally defined term used to describe what your question is
    really about. The answer--plain and simple--is that if you have a 50mm lens on a 6x6
    nominal format Hasselblad and then use it with a back which masks out the image to a 6x4.5
    size, the amount of useful image area will be the same as if you had put a 62.5 mm lens on
    the camera and used a 6x6 film back. (Overall, you lose 25% of the negative or transparency
    area.)
     
  8. Oh, I see, thanks. I did not know the backs were actually optimized/intended for 6x4.5 format. I thought there were separate ones for the 6x6 format.

    Best Regards,
     
  9. Anastas

    The digital 'crop factor' affects the image exactyt as if you had masked down the film gate, which will give a reduced angle of view, but, still referring to the 50mm lens [your example] you will get an image that equates to that given by a 75mm, but the lens used doesn't alter with regard to focal length and dof etc.
    Bruno
     
  10. Anastas,<br><br>Different backs do indeed have different sensors, and with that different crop factors. Crop factors differ depending on what format you are comparing the sensor size to as well, of course.<br><br>There are two (three, depending on how strict you are) sensors in use in Hasselblad backs, one measuring 36.7 x 49 mm (132C, 528C, CF39, CFH39), aspect ratio roughly equivalent to 6x45, and another, square one, measuring 36.9 x 36.9 mm.
     
  11. I use the Phase One P25 back on Hasselblad V bodies. The P25 sensor size is 37mm x 49mm, but the sensor mask pretty much fills the focusing screen.

    I wonder if Hasselblad crops the film with their viewfinders, or maybe it's a perspective effect when looking into the viewfinder? Either way there's so little free space around the mask in the Hassie viewfinder that for practical compositional purposes it's the same as using film if you intend cropping to a rectangular format.
     
  12. In the 4x5 speed graphic days; folks used 4x5 film, roughly 3x4 polaroid; 6x7cm roll film , 6x6 roll film and now I use a 7x10cm phaseOne scan back. The term "crop factor" seems to be a new term it seems. It use to be that folks understood that angular coverage was less when a smaller format was used. Before zoom lenses were common; folks ofen got Exakta to c mount adapters; C mount to d mount adapters for their 16 and 8mm movie cameras. Camera stores even gave away a free circular slide rule for diagonal angular coverage versus lens focal length when one bought an adapter. These "analog computers" often went from 8mm cine, 16mm cine, 1/2 frame 35mm ; full frame 35mm still, 6x6cm; 6x7 cm, 6x9cm, lantern slide 3x4"; 4x5", 5x7", 8x10" etc.
     

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