Regarding a feature visible in a digital image described as "0.12 pixel in size", does the fraction of a pixel refer strictly to size, or is brightness also involved?
It refers strictly to size, however I believe reducing the size of a light source reduces its luminance exponentially.
To get to an eighth of a pixel, you have to use something called an compression algorithm. I don’t understand how it works, but my husband has done something like it. Here’s a link to a reference book that explains it. books.google.com/books?id=5o4YR0dFcacC&pg=PA140&lpg=PA140&dq=1/8+pixel&source=bl&ots=kooxfxJKSz&sig=ACfU3U0v5l-x7Jm_tEvz_iIB5yR3rxV9zQ&hl=en&sa=X&ved=2ahUKEwitq_DF5L7gAhUKPN8KHasdA1kQ6AEwH3oECAgQAQ#v=onepage&q=1%2F8%20pixel&f=false
It refers to the size of the object in relation to the size of a pixel on a given digital image. “Dimness” wouldn’t relate in any way.
You are speaking a foreign language. One, I do not understand.
You can’t have a fraction of a pixel. What is they are referring is the angular size of the Earth is that small, but there was enough light to register on that one pixel of the CCD.