Originally Posted by charjohncarter
And when you figure it out and have a CLA hope you don't get this on the first roll back: someone said it was shutter bounce??
Kodak 400 Max expired
by John Carter
, on Flickr
So be careful who you use for a CLA.
that is the first curtain rebounding into the edge of the film gate. It's a great example of what it looks like. You can see the basic exposure is consistent right across the film gate, the relationship between the two curtains looks good. But, when the first curtain has ended its run, the edge has rebounded back into the film gate over a few milliseconds, and that strip has not received the full exposure that the majority of the negative got.
It can be caused by curtains that have been over tensioned to compensate for a dirty or worn mechanism instead of getting it back to an acceptable condition. I'm not suggesting the person who worked on your camera did this. The fix could be as simple as adjusting the curtain brake which is meant to prevent the curtains rebounding when they have been set to the correct running speed.
The shorter the exposure time is, the greater a percentage of the nominal exposure this bounce event will be and hence, the easier it becomes to notice. By the time you have dropped the shutter speed to, say, 1/60 or even 1/125, whilst the bounce will still be happening, in most shutters that use the same curtain travel speed at all times, as a percentage of the nominal exposure time the bounce reduction in exposure is so insignificant that its effects are not usually visible.