Film exposure issues

Hello all, this is my first thread, and hopefully the start of many more!

I've just delved into the world of film, and there are some shots of the London underground which are pretty much unusable. The rest of the shots (some underground even!) are perfectly fine. I'm really hoping that it's nothing wrong with the camera I'm using (a Canon A-1 with a slightly eroded mirror, which technically shouldn't affect the image). I just need to know about the problem, but ways of fixing it would be absolutely great. Thanks! :)

Both look badly underexposed. It would be helpful to know ISO and if at all possible what you can recall of the exposure info. Flash used? It's harder to diagnose film issues because unless you wrote down the info usually all we get is ISO. Two possibilities, underexposure in camera or under development. If some of the frame on the same roll are good then it's probably in camera. If one roll is consistently dark it's more likely underdevelopment.

Also, any chance the film was run through an airport baggage screening machine? X-rays are death on many film stocks. Again it would affect the entire roll not random frames.

The other possibility is that even though your ISO and corresponding exposure values are correct, the clockwork that drives the shutter is unreliable or the shutter itself is not timing properly. Does the camera make any unexpected noises when the shutter releases? Canon film bodies of that age had a know issue with the shutter mechanism. It was called Canon Squeal. If you have it you'll know.

The bright lights look properly exposed though, how were you metering for the exposure?
Or did you forget to change the exposure on the first few shots underground perhaps.

I was shooting with a Kodak Ultramax 400, and as far as I can remember the camera was set to shoot at 400 iso for the whole thing. These pictures were taken halfway down the roll anyway, so it's can't be the metering issue.
Forgot about the x-ray, the film must have passed the darned thing at least 4 times now. The pictures still look decent so I hope my undeveloped slides aren't affected as well. Or are they more prone to high-frequency waves?
I haven't really heard a squeal, and judging by your comment it's meant to sound quite prominent.

Cheers!

You say other frames from this roll are exposed OK? What's different, if anything, about the conditions?

Were you shooting Aperture priority, shutter, manual, or program?

I had an AE-1 whose shutter wasn't timing incorrectly, but the rear curtain would stick partway across, leaving a slightly brighter vertical bar, which I see in 3 places on your second picture.

I don't recall what metwring modes the A-1 had other than the basic center-weighted averaging. I don't think this is a metering problem. I kinda think the camera was set out of range, i.e. shutter priority with a speed too high for the maximum aperture.

It would be interesting to see some of the good pictures to compare their situations. And are these scans of the prints, or the negatives? You have to use the negatives, really, to get an idea of what the camera did, because there's absolutely no telling what the photo lab did with the prints. I say that because the second one is not so much dark from underexposure, it's washed out with a lack of contrast, which tells me it's a print the lab tried to save by pushing their machine's buttons.

(Of course, the problem becomes that to scan the negatives you have to have a film scanner, which isn't cheap, or a flatbed scanner with adapters, which can be horribly inaccurate!)

the second one is not so much dark from underexposure..

I do not want to say anything about this matter -- Film Exposure Issues. So i want some time to take my Decision about it.