Patt 743 Painted Lenses

[charl.ie]

Hi All,

 

We've been going through our yearly maintenance, and have finally gotten round to attempting to fix our lot of broken Patt 743s. We have found that some of the lenses have black paint around the outside of the ridges, whereas others don't (black on right, normal left):

 

 

Any ideas as to why some are painted? Were some sold like that, or have they been a victim of an unfortunate accident? Should we clean it off, or does it make no difference?

[Whiskers]

Colouvred risers, the black on the steps of a Fresnel lens, Strand sold these as an option in 60s and 70s /c was the designation, They were sposed to reduce the spill outside the beam of a 123 / 223 They were produced in batches and you had to wait until there were enough orders before they would make yours. Did not do a lot in practice but as the rising surface contributes nothing to the beam its probably OK to leave them.

[csg]

They were sold like that as an option, called "colourved" or something like that - the idea was to reduce scatter. I would leave them alone, reduction in light output in the main beam should be negligible.

[IRW]

A similar thing to the modern 'concentric rings' then?

[vinntec]

A similar thing to the modern 'concentric rings' then?

Ah yes, spill rings and a parabolic reflector - now you are talking! Oh concentric rings you say, better put my walking stick away then. Although looking at images on Google suggests they are not much different - come back Pageant, all is forgiven!

[gareth]

A similar thing to the modern 'concentric rings' then?

 

 

The same principle, yes. The photo actually gives a pretty good insight into how/why the idea works - the point on the lens which is directly beneath the camera is showing virtually no black at all, but the further 'off axis' you get the more black becomes visible.