Are the black blobs on these pictures indicative of shutter failure on my Canon 5D (mark I)?
They started to show suddenly, ie. I saw nothing resembling that before on my pictures and starting from certain photo they are always there. They are only visible on photos taken at shutter speeds faster than 1/250 sec: these photos (of the sky) were taken at increasingly higher shutter speeds: at 1/250 it’s still ok, at 1/320 grey shadow starts to appear in the lower right corner, turning into black blob at around 1/640 and reaching almost maximum at 1/2500. Please, ignore the upper right corner, it was difficult to get a clear shot of the sky in the middle of the city and the slight shadow there might be a nearby tree.
Other photos taken at different apertures and with different lenses (or without a lens), with a mirror lockup, with synchronization on 1st or 2nd curtain look more or less the same.
I raised the mirror up (using 'Clean sensor' option) and there's nothing obviously wrong, ie. no parts of the shutter are sticking out and sensor looks reasonably clear.
Any ideas what this could be? And if so, is there anything reasonably simple that could be done "in the field"? (I'm NOT a photo technician!): I still have around one month of travelling in Laos/Thailand to do and probably will only be able to send 5D for professional repair once I' back in Europe.