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Crop Factor on H4D-40 for HC 35mm

P

Psmith2383

New Member
I need a wide angle (moderate) to add to my 80mm that came with my H4D-40 body. I've research the concept of crop factor and how size of digital back (in my case a 40gb) influences what working focal length you receive when you use a lens, say a HC 35mm. I've received three responses from seemingly knowledgeable sources. Tech Support at Hasselblad USA told me to the crop factor for the 40gb back is 1.1 for any of the lenses in the H category. Then told me that if I wanted a wide angle (similar in look to a 28mm lens on analog camera, I should buy the HC 50. Doesn't make sense. Then I read in the Journal of British Photography (that suggested a factor of 1.3.)

I've also read that the sH4D-40 has a crop factor of .76. So my HC 80mm that came with the camera actually looks like a normal lens with a tiny increase in focal length, around 60mm. And it does.

If I buy a HC 35 mm, multiplied by a factor of .76, that would mean that the 35 would render an image that would look as if it were shot with approximately a 28mm lens in a 35mm analog camera.

Is my thinking here correct on how to determine the working focal length when using smaller backs like the 40? Phil
 
The crop factor of your digital back is 1.1 when referenced against a 6x4.5 cm image. You are basing your requirements against a 35mm camera which is a smaller sensor again, which means the 6x4.5 has a crop factor of 1.6x compared with a 35mm frame, ergo:

80mm lens on a digital back will give a similar AOV to a 72mm lens on 6x4.5 which in turn will give a similar AOV to a 45mm lens on 35mm
65mm lens on a digital back will give a similar AOV to a 60mm lens on 6x4.5 which in turn will give a similar AOV to a 37mm lens on 35mm
50mm lens on a digital back will give a similar AOV to a 45mm lens on 6x4.5 which in turn will give a similar AOV to a 28mm lens on 35mm
35mm lens on a digital back will give a similar AOV to a 31mm lens on 6x4.5 which in turn will give a similar AOV to a 20mm lens on 35mm

Returning to your original question it would seem that you would require a 50mm HC lens which would equate to a similar AOV as a 28mm lens would on 35mm
 
Continuing on with the longer end of the range of HC lenses:

300mm lens on a digital back will give a similar AOV to a 273mm lens on 6x4.5 which in turn will give a similar AOV to a 170mm lens on 35mm
210mm lens on a digital back will give a similar AOV to a 191mm lens on 6x4.5 which in turn will give a similar AOV to a 120mm lens on 35mm
150mm lens on a digital back will give a similar AOV to a 136mm lens on 6x4.5 which in turn will give a similar AOV to a 85mm lens on 35mm
120mm lens on a digital back will give a similar AOV to a 109mm lens on 6x4.5 which in turn will give a similar AOV to a 68mm lens on 35mm
100mm lens on a digital back will give a similar AOV to a 91mm lens on 6x4.5 which in turn will give a similar AOV to a 57mm lens on 35mm
 
As Ed posted,
you appear to be confusing the two different factors.
The H4D-40 does not have a full frame 6x4.5 sensor, hence the 1.1 crop.
The other factor is the FOV when compared to 35mm.
These are quite difficult, and only serve as guides due to the different formats.
Ed's values are a good guide.
HTH, S.
 
Thanks from Phil

I want to thank you for sharing your knowledge and for suggesting an appropriate lens. I'll see if I can find a dealer to allow me to use lens in shop to see if it works for me. Phil
 
Information Error.

>The H3D/31, H3D-II/31, H4D/31 and H4D/40 are crop frame with a 1.3X crop factor compared to full frame 645. The sensor of the 31 and 40 meg backs are the same size.

The 31 and 40 meg sensors employ micro-lenses and provide an ISO range from 100 to 1600. The H4D/40 is the newer sensor design and improved the ISO response by about one stop or so ... i.e., ISO 1600 from the H4D/40 looks as good or better than ISO 800 from the 31 meg backs, and so on.

>The 39, and 50 meg backs are a 1.1X crop factor compared to full frame 645. The ISO response of these backs is 50 to 800. The 50 sensor is a slightly newer design and improved the ISO response a bit. Neither employ micro lenses making them suitable for use on tech cameras with movements without color cast, etc..


>The H4D/60 is as close to full frame 645 as you can get without actually being full frame. Unlike all the previous Hasselblad backs that use a Kodak sensor, the H4D/60 employs a Dalsa made sensor with ISOs from 50 to 800.


LENSES:

The lenses with the "HC" prefix (i.e., HC-50/3.5) are full 645 coverage ... ALL of which were initially designed when the H camera could be used with either a digital back or a 645 film back ... the last of which was the H3D and H2F. H1 and H2 cameras also could take a film back and any other digital back, like from Phase One or Leaf. As of the H3D, Hasselblad closed the system to other backs and began integrating the camera with their backs only. Only with the recent H4X, was that reopened for other makes of DBs.

The lenses with a "HCD" prefix are digital era designs (i.e., HCD-28/4) and cover the 1.1X sensors, but slightly crop the larger 60 back and cannot be used on the film capable cameras. The 35-90 is also a HCD lens. So I presume the crop factor on a 31 or 40 meg sensor would be 1.2X or a bit less.

In medium format terms, the HC lenses are simply a 1.3X formula on the 31 and 40 backs. HC-35mm = 45mm field-of-view. A HC-50/3.5 = 65mm field-of-view

The HCD lenses on a 31 or 40 meg back are around 1.2X ... so a HCD-28/4 = 33.6mm field-of-view.

The above are Medium Format numbers ... and then can be translated using format calculators to arrive at approximate 35mm format equivalents.

-Marc
 
thanks for clarifying misty area

Marc: your carefully drafted response added so much to my understanding of the relationship between lens and back and resulting image. Equally helpful is your distinction among the different mutations in the H series. I'm confident that your response was helpful to many new to the Hasselblad H series. Phil
 
No problem Phil. Anything that helps.

I know much of this because I've owned and used all of them from the H2D/22 onward ...including a few CFH cameras which you don't hear much about, and a more recent stint with a H2F camera I used to shoot film, and also used a CF/39 Multi-Shot back on it ... which could be mounted on most any make of Medium Format Camera by means of Hasselblad's iAdapter system.

Sadly, the multi-mount CF backs are now discontinued. The only CF back still available from Hasselblad is the dedicated CFV/50 made for use on the legacy Hasselblad V cameras like the 503CW or 203FE (200 series cameras require a slight factory modification).

Of note: the classic manual focus Zeiss CF, CFi, and CFE lenses used on the classic 500 series V cameras can also be used on the H cameras via the CF Adapter. In particular, the CFE 40IF is quite a performer ... but produces about a 1.5X crop factor, so would be approximately as 60mm field-of-view on a H3D/H3D-II/39 and H4D/50. While these Zeiss lenses are manual focus, the H cameras will perform focus confirmation in the viewfinder. BTW, Hasselblad has included DAC software corrections for most classic Zeiss V lenses.

Lastly, All current HC and HCD Hasselblad lenses can be used on the Leica S2 via the recently available Leica H to S adapter while retaining full AF and auto metering functions ... the difference being that the S2 is a dual shutter camera, so the H lenses can be used in Leaf shutter mode up to 1/750 flash sync, AND up to 1/4000 in Focal Plane Mode. I also have a S2 and use my Hassey lenses on it regularly. Leica also included DAC type Light-Room software corrections specific to using these lenses on their S2 camera, so the 28mm etc. is fully corrected just like it is when used on the H cameras.

Now you know more than you wanted to ... LOL!

-Marc
 
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