problems with P25 and long exposures

[michaelnotar]

i dont have a explanation for this, perhaps you can help.

it seems with exposures of 90 secs or longer, the right side of the image does odd things. in these scenes it developed a yellow bar that turned green and more pronounced as the exposure time increased, and in very long exposures of 4minutes or longer it went black too on the right edge.

i have some shots of a dusk shot where the outside is mainly blue and it the right side of the image when purpleish... kindof interesting how the right side is a color close to the rest of the image in both case.

P25 with 35mm lens on cambo wds, Time shutter position, Capture one one shot cable, processed in captureone 4 (also appears in v3 and ACR).

2 images attached. entire kitchen photo at 2 mins, sink closer photo at 4mins.

[jmboss]

michaelnotar,

Are use using a P25 or a P25+ ?

If your using a P25, Phase One only specs the digital back at 32 seconds maximum exposure time.

If your sample photos are taken with the P25 model, I would consider yourself fortunate that your images look this good.

Joe Bossuyt

[michaelnotar]

i have the regular P25... and i can have up to 90 sec exposures without any difference.

also i have seen the odd image problems at iso 50-200, so it doesnt appear to be just one iso.

[Panopeeper]

also i have seen the odd image problems at iso 50-200, so it doesnt appear to be just one iso

The ISO setting does not change anything on the image; it is only for the evaluation of the exposure.

Do you mind uploading this greenish raw file via yousendit? Some black frame shots (lens cap on, viewfinder sealed) too would be interesting, with different shutter times (like 30sec,  60sec, 120sec and 240sec).

[jmboss]

michaelnotar.

This was the explanation that was emailed back to me by Dave Gallagher at Capture Integration a little over a month ago:

"The P25 and the P20 were the first two P backs introduced.  With that, they have the same internal processing unit as the H20 and H25 but with the added heat of the battery, LCD, etc.  The assumption was that they could have the same exposure times as its H predecessor but they were wrong.    So, yes, the maximum exposure with them is somewhere between 30-45 seconds depending on the conditions.  Anything more than that will create a discoloration on the CCD near the battery."  

So it looks like your P25 is doing a really good job.

I wish my Leaf Aptus could do this.

I wonder if you could achieve even cleaner exposures by removing the onboard battery and using the FireWire terminal for power to your P25.

And if your first couple of long exposures produce the cleanest files; while the back is still cold.

Joe Bossuyt

[michaelnotar]

thanks, thats interesting and the right side of the image is the side by the battery so that makes sense.

i had problems with the FW powering the back, files dont teather and get messed up in transmission... so i bought the no power FW cable adapter which forces the back to use the on board battery.

hmm well i need those long exposures, those were dusk shots, i can understand if it was significantly longer, but at iso 50 f8-11 w/center filter of 2 stops 1-4mins exposures are the norm.

curious to know if my dealer is willing to work with me to trade towards a P25+ for a reasonable amount or perhaps there is a work around or something.

[DavidP]

Since the image is inverted, wouldn't the right side of the image be on the left of the back?

I had a P25 before and I would sometimes get that green edge shooting with strobe and shorter exposures when tethered to a mac laptop. I thought it might have something to do with not having enough power through the fire wire port, it never happened in the studio with a tower computer.

I never tried that long an exposure with it.


"thanks, thats interesting and the right side of the image is the side by the battery so that makes sense."