Luminous Landscape Forum

Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: chrisg77 on June 14, 2009, 01:22:23 am

Title: Green "flare" on Phaseone H25 with Flexbody
Post by: chrisg77 on June 14, 2009, 01:22:23 am

Does anyone have an idea what would cause this green "flare" consistently from the left? It is intermittent in that is comes and goes (almost 50% though), but I have no idea why.

The setup:
H25 back tethered to MacBook Pro w/fw power boost or Powerbook G4
Hasselblad Flexbody w/ multiple lenses (120mm CFi, 80mm CF)
Sample images were shot with strobe illumination, shutter speed 1/125s, f11.

The Flexbody is new to me and I'm NOT getting this with either 201F body or a Cambo wide camera. Not a light leak due to being intermittent and rotates with back when back is mounted vertically. I've switched lenses, FW cables, laptops, covered Flexbody in dark cloth to no luck. As well this is not related to shifting or tilting as I get it at all zero on Flexbody as well. Somehow this seems tied to the Flexbody, but always coming in from the left of a horizontal frame (bottom on vertical). Intensity does vary and will come and go. As you can see from the vertical images, when I remount the back vertically 'it' still flares in on the same side.

Is this a dark calibration issue, something with the Flexbody shutter release? The only maybe solution (rubber chicken dance) that seems to get a reduced occurrence is to do the following: Fully cock Flexbody, release first to close diaphragm, wake back and count 3sec., release shutter. The waiting to release after waking the back seems to be the key step.

Example Images:
(http://www.arch-clig.com/test/h25/Test2_036006.jpg)(http://www.arch-clig.com/test/h25/Test2_035994.jpg)

Same without Green:
(http://www.arch-clig.com/test/h25/Test2_036004.jpg)(http://www.arch-clig.com/test/h25/Test2_035997.jpg)

Thanks
Chris

Title: Green "flare" on Phaseone H25 with Flexbody
Post by: Rick_Allen on June 14, 2009, 01:30:20 am

its a result of the lens shutter not closing at the same time that the flash sync port signals that its closed. Usually cleaning the flash sync port will fix it. Seems strange that you are getting it with different lenses. Have you tried different wake up cables?

Title: Green "flare" on Phaseone H25 with Flexbody
Post by: Dustbak on June 14, 2009, 02:54:43 am

I had this phenomena with my Hasselblad back and flexbody. The same lenses on a 503CW worked flawlessly, it turned out my Flexbody needed a CLA, specifically the release mechanism. It was indeed a sync problem between shutter and back. Your problem looks like the same thing even though with me it wasn't green but magenta.

Title: Green "flare" on Phaseone H25 with Flexbody
Post by: chrisg77 on June 16, 2009, 07:02:44 am

Thanks both Dustbak and Rick, much appreciated feedback. I think I'm in agreement that the body needs a CLA and that the cause is the release mechanism. Similar to Dustbak the problem occurs with multiple lenses while the same lenses work perfectly on 201f body. As well tried multiple wake cables and get green on both (they also work fine on 201f body). I will ship off the body and if I learn anything more I'll try to post here again for others down the road.

Thanks again.

Title: Green "flare" on Phaseone H25 with Flexbody
Post by: Phil Indeblanc on June 16, 2009, 02:07:46 pm

I don't use the Flex body, but I have had this happen....As mentioned, I think it is a sync/timing issue. With wakeup cable timing,  I have also noticed it interrupt the flash causing it to not fire. It is hard to get into a somewhat fast pace with the wakeup cable.