Using GPUImageLookupFilter on a movie file produces black screen

Using GPUImageLookupFilter on a movie file produces black screen

I am moving my code over from a still image application to one that
produces movie files. There is a problem however with the following code
where the final output is a black movie screen using the
GPUImageLookupFilter filter. Can anyone spot what I am doing wrong or what
I may have missed.
GPUImagePicture *lookupImageSource = [[GPUImagePicture alloc]
initWithImage:[UIImage imageNamed:@"ExtremeVintage1.png"]];
[lookupImageSource processImage];
filter = [[GPUImageLookupFilter alloc] init];
[movieFile addTarget:filter];
[lookupImageSource addTarget:filter];
Thanks