UV filters from 70s going purple??

[Archiver]

I just noticed something weird. The UV filters on my old Minolta and Pentax lenses have a purplish tint to them. They are Hoya Skylight 1B filters, bought when Dad got the lenses back in the late 70s. The lenses were kept in a cabinet or wardrobe for years until I got them out in the mid 2000s. Yesterday, I decided to give them some sun and a clean by the window, and noticed that each filter has a purple tint that is clearly visible when placed on a white background. None of my other UV filters that were bought from the mid 2000s onwards have this tint.

Would the filters have had this tint when originally purchased? Surely not. Has anyone seen this before?

--- Okay, I just looked up the Hoya Skylight 1B filter and found that not only are they still produced, but they are supposed to have this tint! It is intended to reduce the blue in bright daylight photography. I had no idea about this! What a fun and random thing to learn. And I thought there was something wrong with them, hahaha!

 

[zuikologist]

I had thought the pink and purple tinted UV filters are the higher quality type and the lower cost usually grey tinted filters are of lower quality/lesser or no coating.

 

[weizenkeim]

don't know if it has s.th. do with the quality but some filters always had this purplish tint.

 

[joe bosak]

Yes I went through this too: a skylight filter is not the same as a uv filter. Seems skylight filters are really from the film days.

 

[Archiver]

Yes I went through this too: a skylight filter is not the same as a uv filter. Seems skylight filters are really from the film days.

I'd never even heard of a skylight filter. What's funny is that Dad had these on all his lenses from the late 70s. Minolta MC and MD Rokkor and Pentax-M SMC. It was really odd to see them side by side, all the the same tint.

 

[Dwig]

Real Skylight 1A filters are slight tinting filters and will have a very slight pinkish tint visually. Their tint will be doubled if viewed with a white card when the light striking the card passes through the filter to light the card and back through the filter again to be viewed.

Real UV filters are more of a band-pass or cut-off filter. Over most of the spectrum, they pass all light uniformly but sharply attenuate the very high frequency blue/violet end of the visible spectrum and the near UV portion. These generally look very faintly brownish to the eye. Some are "stronger" than others. That is, their cut-off frequency is slightly lower, deeper into the visible.

Both filters lost all photographic value by the mid to late 1960s when the problems that they were made to fix were fixed in the newer color films' layered emulsions. They should have fallen off the market, but some marketing wizard grabbed onto the idea that they could be sold as physical protection for the lens. Given the extremely high markup on filters, this gave retailers a big incentive to push the idea.

Since modern (read: last half century) usage doesn't involve any real filtering, today's UV and so-called Skylight filters don't need to have any particular spectral absorption curve they are generally very weak and lack some of the more expensive materials/dyes (real classic Skylight 1A often used some expensive chemical components).

 

[DownUnder]

For about ten years from the late 1990s I went through a Purist phase and had all of my Nikon skylight filters removed and replaced with clear optical quality glass. I had read about this in a book by a travel photographer-writer of that time, and thought this would be the way to go.

By the mid-'00s the cost of quality optical glass and the work involved in fitting it into Nikon filter frames was high and I gave up doing this. I still have ten or so clear optical filters on my AFD lenses. Close inspection of my (now almost all digital) images show no color cast at all, whereas the original skylight glass gave my images a slight reddish tint.

Anecdotal, yes. I can't recall who the author of that travel book was as I no longer have it in my library. She was a well-known American (lady) photographer of that era. Someone may remember her. I think the book was one of the then-popular Petersen guides.

I also have a small fortune (everything cost more in Australia, then and now) invested in Nikon B&W filters, in fact the entire range. The ambers and blues I usually avoided unless they came my way secondhand and dirt-cheaply, so I have a few. Ditto the old Nikon F era polarisers, somehow I've managed to acquire about six of them, in their lovely leather cases. Antiques.

All this is now the stuff of past memories, ha!

Dwig (#6) summed it up well for me. The '60s was the era when we mostly used B&W filters. Now, nobody does much.