Welcome to the wonderful (vast, and deep) world of LF!
Re Mark's comment above - I have a 300/500 convertible Symmar (from around 1962) and have read a little about it... Converted (at the longer length with the front unit removed) apparently these lenses have chromatic aberration. I think this means that the different colours (wavelengths) of light no longer converge at the same place on the image, and causes a softness in the corners away from the centre of the image. I'm intrigued myself, as I have an interest in softer focus lenses.
I have read that you can compensate somewhat for the loss in quality by using a yellow or orange filter (if the latter you would probably need to compensate by one stop). As you're unlikely to find a filter that will fit the front threads of the shutter you may have to just hang it there or bodge a filter with some tape to make it a 'push fit'. I think you would need to focus with the filter in place.
Just to emphasise - this is only when the lenses are converted (front unit removed).
Bookmarks