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Problem with pin-point light sources
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Adrian


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Registered: May 2012
Location: Yateley in Hampshire
Posts: 204
users gallery
This was a time-exposure (25s at f/16). What are the fine streams of light coming from the bright lights in the picture? I've not seen anything like this before. Any suggestions as to what is causing the problem and how to correct it? It's not a printing problem (visible on the negative). The film was developed on a spiral in a tank with agitation 15s every minute. Another frame (of the same picture, same exposure) has exactly the same characteristics.
Date: Sun, 20, January, 2013 Views: 2628
Filesize: 39.0kb, 110.3kb Dimensions: 989 x 999
Additional Info
Keywords: Problem with pin-point light sources
Film make, size & rating:: HP5+ 120, EI300
Film developer & temp:: HC110 1:33, 20C
Lens focal length, aperture & speed:: 80mm f/16, 25s
Tripod used Y/N:: Y
Paper:: MGRC-IV
Paper developer & temp:: IMG 20C

Author
Thread  
Martin Aislabie

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Registered: November 2008
Location: Stratford-upon-Avon, England
Posts: 1,608
Tue, 22, January, 2013 7:35pm

Looks to me like the film has been wound on while the shutter is still open.


Its the only reason highlights get dragged down the negative - nothing else was bright enough to leave an impression on the film.


Martin
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Keith Tapscott.

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Registered: June 2009
Posts: 961
Wed, 23, January, 2013 6:37am

It is definitely a flare problem. All of the streaks are in line with the lights.


Try again at a wider lens aperture, providing it gives adequate depth of field and see if that helps.
You didn't mention which lens you used on your camera or if a lens hood was used.


As Martin mentioned, you may have wound the film with the shutter still open.
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Adrian
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Registered: May 2012
Location: Yateley in Hampshire
Posts: 204
Thu, 24, January, 2013 1:04pm

Thanks for the comments Martin, Keith.


I used an Zenanon 80mm lens (the camera is a Bronica SQa) without a lens hood. The shutter was set to "T". I used the mirror lockup too. I suppose the shutter must have shut once I released the cable release. I then wound on the film which re-engages the SLR mirror too.


If it was a flare problem, why would the streaks only go down the film. I would have thought they would have gone upwards too. But I didn't have a lens hood, so it could be flare I suppose. I didn't notice the streaks in the view finder.


If it was film wind-on, then I understand why only the brightest features show up, but why would the streaks fade-out or end?


It's still a mystery. I'll check out the camera to see (a) if I can get it to flare and (b) take a close look at what the shutter/winder does in "T" mode.
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MartyNL

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Registered: September 2010
Location: based in The Netherlands
Posts: 2,447
Thu, 24, January, 2013 8:53pm

Hi Adrian,
It's commonly the case that the "B" bulb setting opens and closes on one press of the shutter release. Where the "T" time setting takes 1 press to open the shutter and a second press to close the shutter... But I'm not familiar with your camera.

------------------------------
MartyNL
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Adrian
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Registered: May 2012
Location: Yateley in Hampshire
Posts: 204
Thu, 24, January, 2013 11:00pm

Ah! It turns out I wasn't familiar with my camera either. I've just had a fiddle with it (no film in) and found that in order to shut the shutter one has to slide the "T" control to the normal "A" position. Pressing the shutter release again or advancing the film doesn't close the shutter. So what I did is open the shutter, make the exposure then relaxed the shutter cable (and as you say that's "B" style operation not "T") then wound the film on. The shutter remained open all the while I was doing this and won't have shut again until I'd unmounted the camera from the tripod and re-locked the shutter in the "A" position.


The trouble is, I rarely use long exposures on my Bronica SQ so had forgotten how to do it properly.


Mistery solved!


Thanks.
Adrian
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