Magenta images with a Blad

[Justinr]

I'm afraid that I can only be a little vague on details here but today I met a lady having problems with an early Phase One back (tethered) on a Hasselblad. Basically she is getting magenta images on exposures longer than 1/8th with her standard lens. The lens has been checked out and seems fine but it doesn't do it with any other of her optics. I was able to have a quick play with her image in PS and it seems to me that it just stops recording the blue and green channels between 1/15 and 1/8th. To my shame I don't know my Blads so can't say which model the body or lens is, nor can I tell which model of Phase one back she has but may be able to find out if necessary. She hopes to try the lens with a different back soon but my hunch is that it's a sensor/digital problem rather than a lens one.

Justin.

[Nick-T]

I'm afraid that I can only be a little vague on details here but today I met a lady having problems with an early Phase One back (tethered) on a Hasselblad. Basically she is getting magenta images on exposures longer than 1/8th with her standard lens. The lens has been checked out and seems fine but it doesn't do it with any other of her optics. I was able to have a quick play with her image in PS and it seems to me that it just stops recording the blue and green channels between 1/15 and 1/8th. To my shame I don't know my Blads so can't say which model the body or lens is, nor can I tell which model of Phase one back she has but may be able to find out if necessary. She hopes to try the lens with a different back soon but my hunch is that it's a sensor/digital problem rather than a lens one.

Justin.

Well I'll let the Phase guys chime in but here's two thoughts.

On V system with longer than 1/15th (from memory) you must hold the shutter release down until the shutter has closed. Otherwise the mirror will start to move before the shutter has closed causing ghosting.


Second with older Imacon backs you had to tell the back if you were shooting longer than  1/8th or it would cause pink streaking. Is there a setting in the back menus or tethered software where you can set the exposure time?

Hope that helps.
Nick-T

[ThierryH]

I would "guess" as Nick: most probably the activation time of your sensor isn't long enough for the exposure time used, thus causing light hitting the sensor when it already reads out.

Try to increase the "exposure" time in software, if possible, always AT LEAST equal to the shutter time, if not longer.

Best regards,
Thierry

[digitalcameraman]

I'm afraid that I can only be a little vague on details here but today I met a lady having problems with an early Phase One back (tethered) on a Hasselblad. Basically she is getting magenta images on exposures longer than 1/8th with her standard lens. The lens has been checked out and seems fine but it doesn't do it with any other of her optics. I was able to have a quick play with her image in PS and it seems to me that it just stops recording the blue and green channels between 1/15 and 1/8th. To my shame I don't know my Blads so can't say which model the body or lens is, nor can I tell which model of Phase one back she has but may be able to find out if necessary. She hopes to try the lens with a different back soon but my hunch is that it's a sensor/digital problem rather than a lens one.

Justin.

Sounds like a bad lens shutter on the longer exposures on that lens. The shutter in that V lens should be sending a signal to the back that is is finished exposing, juts like on film. I would firs test at 125 and 250 of shutter speeds. Then got to the longer ones 1/8, 1/4, 1/2. That is where I have seen many of these V lenses break down and not work correctly. Dirty flash sync can also interrupt the signal that the back is looking for.

If this does not allow you the problem, then I would test another body. The body problems usually return an error that is a two shot time out error.

If it is a P back and not an older one she needs to make sure it it set for short latency to.


Good Luck.


Chris Snipes
Image Production, Inc
Phase One Reseller Florida
Phase One Test Studio

www.imageproduction.com
[email protected]

[Doug Peterson]

The lens can "check out" and still have a lagging shutter. The specifications they use at Hassy for measuring this are often not strict enough to guarantee perfect operation with Phase One backs.

We've had this happen with two lenses (of our customers) in two years.

The solution is to send the lens in again and explain the specific problem is a lagging shutter which is not lagging enough to fail their tests but which needs correcting none the less.

Without all the details it's impossible to be sure, but I'd put very good odds on a lagging shutter.

Doug Peterson
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[Justinr]

Phew!

Thanks for the prompt input gents, I have passed your comments on.

Justin.