H25 starts transmitting before the exposure is complete.

Question regarding:Phase One H25, H20, H101, H10, H5, LightPhase, PowerPhase FX / FX +, PowerPhase, PhotoPhase and StudioKit.
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H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Sat Oct 04, 2014 7:20 pm

I have an H25 mounted on 500C/M. It works correctly at short shutter speeds, but, at anything over 1/8 of a second, it starts transmitting the image to Capture One before the exposure is complete (with the shutter open), causing longitudinal streaking.

The rear pin on the camera extends completely, and the same problem occurs using a different camera body. Rotating the back (so that the rear pin gets read by another slot) does not change the problem either, which leads me to suspect a configuration or software problem. Has anybody seen this before?
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Re: H25 starts transmitting before the exposure is complete.

Postby Ulf » Mon Oct 06, 2014 10:55 pm

Hi

Most likely you have a shutter in the lens which is on the last leg.

Verify with a different lens and contact Hasselblad for service of the lens.
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Ulf Liljegren
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Thu Oct 09, 2014 3:19 am

Hi, Ulf.

I was under the impression that it was the pin on the back of the camera body rather than the flash sync that determined when the back was to stop recording (and to start transmitting), no? I had likewise assumed that the flash contacts were only supposed to short briefly at shutter opening and could not determine exposure length. How does the back determine when to stop the exposure?

In any case, you were right that changing lenses fixed the problem. The lens works beautifully in normal (non-digital) use, so I wouldn't have suspected it. I suppose that I'll need to send it in for service.

Best wishes,

Frank
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Thu Oct 09, 2014 3:37 am

Hmm. I got out the ohm meter, and the other lenses do indeed keep the flash contacts closed for the duration of the exposure, so this lens is definitely doing something wrong.

Anyway, thanks very much for your insight on this.
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Re: H25 starts transmitting before the exposure is complete.

Postby Ulf » Thu Oct 09, 2014 12:28 pm

Hi

The pin of the body simply "wake up" the back so it is ready to capture.
Just like you discovered, it is the lens which specify the length of the exposure.
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Fri Nov 07, 2014 6:46 am

Okay. Now (after a week of everything working fine) I have a slightly different problem.

The transmission now waits until I release the shutter release button, but the exposure is black (all pixels zero). I confirm that the lens shutter and the rear shutter stay open, and I assume that the wait to transmit implies that the lens contacts and the lens cable are delivering a correct signal to the back. I assume that the FireWire cable is not at fault since otherwise the software would complain.

I don't know exactly what I could be doing wrong, but the problem must be with me. I've tried two different lenses, two different bodies, two different backs (both H25), and three different lens cables. I even tried tilting the back off of the camera slightly during the exposure (during the capture sequence blinking with the shutter release depressed) in bright light, and the image still came back completely black (with no underexposure warning, though). How can this be? Where do I look next?
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Re: H25 starts transmitting before the exposure is complete.

Postby Ulf » Fri Nov 07, 2014 11:02 am

Most commonly here is that your computer does not provide enough power.
The only computer that provides enough power is the old Mac Pro.
If you are using Mini mac, iMac, Laptops or any combo with Thunderbolt adapter then you need a power conditioner of some sort.
Phase One makes one, there is also some different types of firewire hubs available which have AC power.
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Fri Nov 07, 2014 5:05 pm

Okay. I'll try that.

Any idea as to why it would have worked and then stopped working? It puzzles me.
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Fri Nov 07, 2014 5:59 pm

Ooh. I figured it out.

I'm running this off of a PowerBook G4. I was using it for a long time with wall power or briefly unplugged with the battery fully charged, and it worked consistently. I tried this again, and it still works consistently in this arrangement. I've been doing field work recently, and I started using the system without wall power, which is when it stopped working. I guess that my car battery + inverter assembly will be following me whenever I do field work in the future.
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Re: H25 starts transmitting before the exposure is complete.

Postby NN635475320989040521UL » Fri Nov 07, 2014 7:02 pm

So, how much power (or how many amps at 12 volts) does the H25 draw at peak? Is the peak only during exposure such that an array of filtering capacitors between the computer and the back would be sufficient?
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Re: H25 starts transmitting before the exposure is complete.

Postby Ulf » Mon Nov 10, 2014 12:53 pm

H25 are 100% IEEE 1394 compliant.
But your PowerBook is not.
That is the problem, it is on the edge and hence why it happens.
With a Mac PRO it would not be an issue.
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Re: H25 starts transmitting before the exposure is complete.

Postby NNN635740972721582801 » Wed Aug 19, 2015 11:16 pm

Ulf wrote:H25 are 100% IEEE 1394 compliant.
But your PowerBook is not.
That is the problem, it is on the edge and hence why it happens.
With a Mac PRO it would not be an issue.


Ulf,

Could you please answer the question about the H25 power consumption (current draw), asked above?

I don't doubt that it is within spec, but it would be useful to know how much power it requires.

Thanks.
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