Hi, A little bit of backstory first.. I recently found my grandpa's old SLR, a Praktica MTL5B with a Pancolar f/1,8 50 mm lens on it and thought I'd give it a go. The camera has an included light meter and on my first roll, it seems to have done a good job. Pictures came out nicely, or as nice as someone who's new to film photography could expect. In the meantime, I also found an old B&W expired film which I thought I'd try as well. The roll is a FORTEPAN SUPER 80 ASA. I know I need to go down 2 stops for every 20 years of age and since the film expired back in 1982, I have to go down to ISO 25. However, my in-camera light meter only seems to work if I set the ISO to 100 or above, so I though to myself I would just meter it with the camera set to 100 and then overexpose 2 more stops. Now. I also downloaded an app for light metering (Pocket Light Meter), but it gives me different results than the in-camera meter. For example, I set the camera to ISO 100, f/2,8 and to expose I had to set the shutter speed to 1/125. The app light meter however was telling me to go to 1/800. I tend to believe the camera since I already shot a roll and worked out fairly well, but you tell me... Can anyone tell me what's what? Thanks so much.