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Hasselblad digital backs and crop factor

A Petkov , Mar 10, 2006; 10:28 a.m.


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


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A Petkov , Mar 10, 2006; 10:30 a.m.

POV should read Angle of View!

Edward Ingold , Mar 10, 2006; 10:59 a.m.

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.

Ellis Vener , Mar 10, 2006; 11:13 a.m.

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.

A Petkov , Mar 10, 2006; 12:04 p.m.

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,

Ellis Vener , Mar 10, 2006; 02:49 p.m.

<I>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?</I><P>

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?

CPeter Jørgensen , Mar 10, 2006; 02:57 p.m.

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.)

A Petkov , Mar 10, 2006; 07:00 p.m.

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,

bruno menilli , Mar 10, 2006; 08:21 p.m.


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

Q.G. de Bakker , Mar 10, 2006; 08:46 p.m.


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.

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.

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