Strange color issue

[spark]

Hi all,
I just encoded my (first) DCP movie from a B/W apple prores source 1920x1080 at 24fps. 150mbps.
DCP-o-matic padded it to 1998x1080 which is fine.
I tested the DCP in two theatres here around and everything was fine.
Then the movie was sent to other cinemas and some projectionist reported a strange issue with not better defined "green stains" over the black and white picture.

During the encoding process i keept all seetings to their defaults. No filters. The "convert from" combobox was correctly set to rec. 709, the same reported by the source prores file.
Audio is 4ch pcm 24bit (L-R-C-LFE)

Any idea?

[mytbyte]

From the top of my head I can only say that it's not the encoding problem if the same DCP played fine on 2 other systems...it's some issue with the paricular system, so others here my offer more ideas, especially if you supply the model of the server and projector in question...

[Carsten]

Find out which server and projector these test showings were played on.

B/W is rare nowadays. They should check wether other commercial B/W stuff displays correctly, e.g. find some B/W trailers.

Maybe they can pause the movie and take a photo with a smartphone and send it over to get a better idea about the issue.

- Carsten

[spark]

Thanks all.
I asked the producer to contact the projectionists in order to know exactly the sever name and better infos about the problem.

As far i know, a BW picture is just a regular picture where the crominance is zero, so why expose those problems only in some cinemas?
In the fact the movie has some colored logos at the beginning, but the most is BW

alessandro

[Carsten]

Some projectors may show color blotching because of dirt, grease, etc. in the lightpath. These may be hard to notice with 'normal' color material, but show up more annoying with B/W footage. Without a better idea what 'green stain' actually is, it is hard to decide what goes on.

- Carsten

[spark]

Well, this is not the case because the backup BD copy worked great on the same projector.

[carl]

Hi,

OK, that's interesting. Do we have any projector details yet?

Can you provide the DCP in question, or perhaps a DCP of a clip of the problematic source file?