Here is an example:
https://www.flickr.com/photos/marcod...2963838558/in/
album-72157705868008995/

The blobs at the top left are the most visible ones, but
there actually are dust blobs across the entire frame.
And apparently the photographer wasan't even aware of
the dust, as the blobs are on all or almost all images.

The camera is a DSLR with an optical viewfinder and I#m
guessing that the images were not inspected during the
trip to Algeria, otherwise the photographer would have
noticed the dust on the sensor.

Actually, looking at the photos of previous trips (the
Namibia one of last summer for instance) the dust on the
sensor was already there, so it seems that the
photographer doesn't even know that the problem exists,
or simply doesn't care. or maybe likes that 'blobby'
look ;-)
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
https://tech.groups.yahoo.com/group/MyOlympus/
https://myolympus.org/ photo sharing site