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Thread: Hasselblad cfv-39 sensor in wrong place

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    Hasselblad cfv-39 sensor in wrong place

    I have been using a Hasselblad cfv-39 Digital Back with great success over the last two years. Used the Digital Back mostly on a Silvestri technical camera and on a 503 CXI body.

    For the last few weeks I have been using a Phase IQ140 V mount Digital Back on a 503 CXI body. The images came out so much better I figured something must be wrong with the Hasselblad Back.

    Using the Hasselblad cfv-39 with a 40mm CFI or 50mm CFI lens I cannot get sharp infinity images until I stop down to F8. Using the Phase IQ140 V mount digital back I get sharp images with the lens wide open.

    The issue is consistent across a few 503 Hasselblad bodies and a few wide angle lens.

    This is not such a big issue for me as I normally have the lens stopped down to F8 or F11 when using a Hasselblad body. But it probably limits the resale of the digital back. Of course when using a bellows Flexi Cam you can focus past where the infinity position stop is, so its not a problem.

    Wondering if I should send the Digital Back to Hasselblad to be recalibrated. It was in this state when I bought it but it's taken me a couple years to work out there is a problem so the guarante will have expired. I think the sensor needs to be slightly further away from the camera ?

    Anyone any experience with getting a Hasselblad back recalibrated ? any ideas of cost and time it takes.

    Any advice on if its even worth doing.

    Regards

    Neil

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    Re: Hasselblad cfv-39 sensor in wrong place

    Neil,

    The New Jersey repair facility would be my first stop. One of the bright spots for Hasselblad is their repair support. They have been very helpful for me in the past, and bend over backwards to satisfy any need you may have.

    Greg

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    Re: Hasselblad cfv-39 sensor in wrong place

    Hi Neil,

    Quick question.

    When you focus to infinity, do you simply wind the lens all the way to the stop?

    D

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    Re: Hasselblad cfv-39 sensor in wrong place

    Greg,

    Yes I also read that hasselblad service and after care is very good. The only problem I have is that I did not realise there was a problem until after the guarantee has finished. I now need to decide if its worth while to get the sensor position changed or not.

    Dave,

    Yes, I do normally just turn the lens to the infinity position. I did check if the lens is focusing past infinity. I worked with the back tethered to a computer and watched what happened as I turned the lens to infinity. I could see I just needed to turn a little more to get really sharp wide open. I also tested with the 250 SA lens which can focus past infinity and of course that lens was perfect wide open

    I am already happy with this digital back as it works so well on a technical camera. Being able to operate with no wires is just great. Now I have discorved it can work even better with my 503cxi than its performing now. its already ok as just set to f8 and infinity focus is ok. but if I got the sensor position changed it would be even sharper. Plus if I want to sell this back in the future it may be a problem for the new owner.

    regards

    Neil

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    Re: Hasselblad cfv-39 sensor in wrong place

    If it were me I'd be it looked at. Nothing more infuriating than equipment you can't completely trust.

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    Re: Hasselblad cfv-39 sensor in wrong place

    You may be right, the perfection side of me says get it adjusted as medium format digital should give the ultimate image quality. But the practical side of me says is it worth the money as I may only just be able to notice the difference in the final print. The difference is only noticeable in things in the far distance from about 1km to infinity. We are talking about only a slight adjustment of the sensor position. I suppose it is the equivalent of something like shimming a digital adapter plate. It's at that level of adjustment. Oh what we have to go through to get the best IQ

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    Re: Hasselblad cfv-39 sensor in wrong place

    you may have two things out of whack, both related to sensor position:

    the lens hits the infiniity stop but has not actually moved close enough to the sensor to bring infinity to focus

    the reflex mirror may be indicating you are in focus when you are not, since that optical path also relies on the sensor position

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    Re: Hasselblad cfv-39 sensor in wrong place

    Yes your right I did notice that both those factors had an effect.

    I tried a few wide angle lens and a few camera bodies. I noticed that it is a little different for some lens. When I reach the infinity stop one of the wide angle lens is sharper than the two others. I tried tethered to a computer and I can see that the lens just needs to be turned a bit more but it has hit the infinity stop so cannot turn anymore. This confirmed that the lens is not focusing past infinity.

    I tried three bodies and it was consistent accross all three of the bodies. So I think the bodies are around the correct calibration.

    I did not use the viewfinder to focus. In the test I had the camera tethered as I wanted to eliminate viewfinder focus as a variable.

    regards

    Neil

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    Re: Hasselblad cfv-39 sensor in wrong place

    Hi Neil,

    Could be a number of factors really! Either sensor position or a lens issue.

    Only way is to get them check out at Hasselblad service. They can check if the infinity stop is in the right place for example.

    Where are you based?

    D

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    Hasselblad cfv-39 sensor slightly in wrong place

    Would want to send the digital back to Hasselblad UK for service. But it's a lot of trouble right now as I am staying in Japn.

    I am still wondering if I am expecting too much here given the precision involved.

    Plus it's swings and roundabouts as I have to stop down the wide angle lens to around f11 to avoid soft corners at which point infinity is sharp.

    So the question is what exactly am I gaining by getting the sensor position calibrated. It may be good enough for the camera and lens I am using?

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    Re: Hasselblad cfv-39 sensor in wrong place

    Managed to sort this problem out without sending the CFV-39 digital back to Hasselblad Denmark.

    I got a clue of what to do from reading the Hasselblad Service manual for 503CW Camera.
    It said “The Camera body focal length is inspected and adjusted by using tool v-2229. The focal length is 71.40mm plus/minus 0.03mm”. So I figured that even a tiny fraction of a millimeter would impact the focus at infinity. This could be in the lens stop, body length or sensor position. Logical thing was to look at the body length as that was the easiest to check.

    I got together as many old Hasselblad V bodies and wide angle lens as I could from different sources.
    Tested with 5 bodies and 9 wide angle lens.

    What I concluded is that there clearly is tolerance variation in the bodies and the lens. Two lens had the infinity stop in the wrong place. One lens focused passed infinity and one stopped way before. Using the other 7 lens I concluded that 3 bodies were in the same ballpark as each other in tolerances. The other 2 bodies were too long and caused the focus to stop before infinity. Of the 3 bodies one was a better match to my digital back than the other two. Logical thing to do was just buy that camera body. ( worked out much cheaper than sending the digital back for service. You would not believe the premium the agent adds to the service price here in Japan )

    The other interesting thing I worked out is that probably the Hasselblad CFV-39 is focusing forward of infinity and the Phase IQ140 back I compared against is focusing a tiny fraction past infinity. The phase one back is probably within an acceptable tolerance. My Hasselblad CFV-39 is slightly out of acceptable tolerance but only just. It is easier for me to compensate by changing the camera body than sending the digital back to Hasselblad Denmark.

    All goes to show that we really do need to match the camera body to our digital backs. This is equivalent of shimming and makes a big difference to infinity sharpness.

    Has anyone else had experiences like this ? It is worth the effort as the Hasselblad V system is a real pleasure to use.

    Regards

    Neil

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    Re: Hasselblad cfv-39 sensor in wrong place

    Neil

    Thanks for the detailed info.

    I had the privilege to test a CFV-50 earlier this month - and was very impressed by the image quality - if the photos were sharp...despite solid tripod and mirror lock-up!

    Taking your info into account may explain our experience.

    It certainly is a joy to use the old V system bodies - I just wish the outcome were more predictable.

    best, S

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    Re: Hasselblad cfv-39 sensor in wrong place

    So let me get this straight. You have just made the argument for Hasselblad to calibrate and sell their digital backs as a unit (as in H4D40-50-60), a decision for which they have been soundly criticized. Hmmm.

    Greg

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    Re: Hasselblad cfv-39 sensor in wrong place

    I have used a Hasselblad V digital back for two years and I thought it was really good. Happy with the images, great results.

    And then... I saw the results from a 503 V body which was effectively matched to my digital back. The difference it makes is shocking. So much sharper out to infinity.

    Really glad I took the time and effort to get this done.

    Regards

    Neil

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    Re: Hasselblad cfv-39 sensor in wrong place

    . So much sharper out to infinity.


    I take this to mean "So much sharper when focused at infinity" ?

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    Re: Hasselblad cfv-39 sensor in wrong place

    Yes that's right. When the lens is set to the infinity stop. The images are so much sharper for far distance objects. Objects a few kilometres away are very sharp now.

    Regards

    Neil

  17. #17
    alexisgc33
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    Re: Hasselblad cfv-39 sensor in wrong place

    Oh man... I just got a 500c/m & a 503cw to use w/a rental Cfv-39 back! hearing this is not cool :'( Anyway you can post samples?

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