Topic: Positives in my negatives

[choppert]

Tally ho,

Sometimes when I develop a film a few of the frames, when viewed at an oblique angle, appear positive.

The tones are reversed and the negative looks like a transparency.

Is there a name for this effect?
Is there a reason it only happens on certain frames?  (my poor recollection is that it mostly happens on underexposed frames???)

Chops

[moominsean]

solarization? often fills in the negative areas, making it look like a positive. not sure why it would only affect a few shots, unless it was happening in camera. any scanned examples?

[LT]

it's a common phenomenon with underexposed negs and is a trick of the light - makes no difference in printing etc ... only you wont have much shadow detail of course.

[Francois]

The principle was widely used in the old days where the glass negative was laid on either black velvet or black lacquer.