Pre-war Angulon f/6.8 90mm filter size

Hi all, I recently got a 1930s 90mm Angulon, quick question. Every reference I've seen indicates a 40.5mm filter thread for the f/6.8 90mm Angulons, but that seems to be a newer version ( I assume same or similar optical formula, but the shutter mounting is different looks like). Mine definitely doesn't have anything like a 40.5mm mount, the only possible thread is around the front element, and looks to be ~24/25mm or so.

So, has anyone got the same older Angulon and successfully used a filter and if so what size ? Or is this not meant to be used as a filter thread at all ? I can't imagine that it wouldn't vignette a bit unless the filter was pretty thin.

Thanks, Daire

Use a push on type filter like a Series filter holder that fits over the outer edge of the front lens cell. Older lenses may have grooves at the front that look like a filter thread, but it is typically either a thread for a retaining ring/lens cell, or to break up specular reflections (ie grooved surface that reflects less light into the lens); not actually intended to take a metric standard thread-in filter.

Daire Quinlan said:

So, has anyone got the same older Angulon and successfully used a filter and if so what size ? Or is this not meant to be used as a filter thread at all ? I can't imagine that it wouldn't vignette a bit unless the filter was pretty thin.

Click to expand...

I've used a step-up ring, from memory a 27-52mm ring but it may have been smaller. It worked and it didn't vignette. But it didn't screw in far so it wasn't very robust.

reddesert said:

Use a push on type filter like a Series filter holder that fits over the outer edge of the front lens cell. Older lenses may have grooves at the front that look like a filter thread, but it is typically either a thread for a retaining ring/lens cell, or to break up specular reflections (ie grooved surface that reflects less light into the lens); not actually intended to take a metric standard thread-in filter.

Click to expand...

Yeah that's what I was thinking. doesn't look particularly as though it's meant to hold a filter, as FotoD below seems to confirm.

FotoD said:

I've used a step-up ring, from memory a 27-52mm ring but it may have been smaller. It worked and it didn't vignette. But it didn't screw in far so it wasn't very robust.

Click to expand...