Due to an over-zealous light meter in an old Praktica SLR, I have a roll of film that's about to be developed that is very much under-exposed. By testing the exposure readings from my Nikon D50 DSLR against the readings of this camera, it turns out I need to set the ISO dial that SHOULD be on 400 down to somewhere between 25 and 50, alternatively when the correct exposure should be 1/30, the camera reads it should be 1/500. In short, the film has been exposed at about 4 stops under (correct my maths if I'm wrong).
Would it be possible to push process this film, with correct exposure, and not have too many negative side effects? How far can an Ilford HP5 400 be physically pushed, or is that a how long is a piece of string question? And has anyone done a 4-5 stop push and had acceptable results/have examples?
It's a rather broad question but I'm just wondering what to expect. I really don't want to have the shots hideously under-developed, but I don't know whether it's salvageable! The other film I had developed using the same readings (C41) came up with some insane green grain, but there are some okay if slightly spooky, grindcore album, photos from it. I just assume that was due to being over-exposed during the scanning phase (hence the grain).
Thanks in advance, Matt.