What on Earth is a K-1 filter?

[John Kasaian]

Hello! I was reading the "aerial photography" chapter in an old Graphic Graphle x Photoggraphy book and it mentioned that an aero 1 filter is similar to a K-1 f ilter. The aero 1 might be useful for the aerial shots I'm taking depending on the filter factor involved, but I'm guessing its unavailable or no longer made, at least in the size I need-52mm--so a K-1 might be the closest thing available, but what is it? I'm hoping it is a #2, which is still made and probably has a f ilter factor my f9 lens can tolerate at 1/250ths. Anyone out there know the an swer?

[Doremus Scudder]

A K-1 is a yellow filter, otherwise known as a number 6 filter. K-2 is the commonest, the number 8 yellow filter. Your 2 filter is lighter, but may work for your applications. The purpose of using a yellow filter in arial photography is to remove the haze caused by scattered blue light. Any yellow filter will do that to some extent. Hope this helps, ;^D)

[James Meckley]

As I recall (my reference books are at home), K-1 is "old terminology" for a light yellow filter, perhaps a 6 or an 8 in modern terms. Should be readily available as a 52mm screw-on. I'll look this up for you when I get home if no one else responds.

[David Karp]

The others are right. These are the "old" filter designations. A K1 is the same as a yellow #6 in today's terminology. It should be no trouble for you to get one in 52mm. My 35mm rig is so old that most of my old 55mm filters have the old designation. I am only 44, where did the time go?

[Per Volquartz]

Dave Karp!!!

44 is no age...and you have plenty of time!!!

[Steve Feldman]

Dave, Per,

Your comments remind me of an old Pete Seeger lyric.

"How do I know my youth is all spend? My get-up-and-go has got-up-and-went. And through it all, I think back and grin. And think of the places my get-up has been."

Oh yes, and a light yellow filter is good to use in b & w portraits also.

Regards, Steve (55)

[John Kasaian]

Thanks for the great advice! As I am staring down the barrel at 50 myself, its reassuring to know that most of my LF photography gear is older than I and still works! Thanks!

[David Karp]

I am not worried about my age. It just surprises me sometimes on the rare occasion when I think about it. I don't feel any different than I did when I first obtained those old designation filters, just not in quite as good shape. (But still good enough to lug my monorail and gear on my back for miles of hiking.) As far as I am concerned, I am just getting started!

When did they change the filter designations anyway? Does anyone know why it happened?