GRAPHIC KOWA 610mm LENS CONSTRUCTION?

[Daniel Strasshofer]

Maybe someone can help to identify the lens construction of my Graphic Kowa 610mm.
6-7 reflections?



https://flic.kr/p/oCSz9t

[StoneNYC]

Sorry to interject,w hat's the reported IC on this?

I've been curious to understand the reflection counting as well so I hope someone answers the OP.

[Daniel Strasshofer]

I can`t find any information for that lens! (Maybe I can find the time to test the IC on my new 12x20", but I have to build a lensboard first)

[8x10 user]

I have never seen a 610 kowa. Nice find!

[John Schneider]

Counting reflections is really more of a dynamic process. Use a point source (like an LED), close the shutter or unscrew the elements so that you're looking at only one element, and then slowly tilt the lens. The number of reflections tells you the number of glass interfaces, the relative intensity tells you the type of interface (air-glass or glass-glass), the direction the reflections move when you tilt the lens tells you the direction of the curvature of that interface (convex or concave), and the speed with which the reflections tells you a bit about the degree of curvature of that interface (i.e., the glass-glass interface on the middle and inner cemented lens elements of a Dagor are unusually steeply curved, so that reflection moves rapidly as you tilt the lens).

And sometimes one of the interfaces is so nearly flat that you have to position the light source just right to see the reflection (which is what I imagine happened in this picture). Assuming so, and seeing that the 7 reflections visible in your pic are all closely grouped (= shallow curves for all interfaces), and making an assumption that a 610 f9 barrel lens is likely a process lens, it's probably the classic 4-element Artar-type construction IMO. But checking the front and rear element separately would be a big help.

[StoneNYC]

Counting reflections is really more of a dynamic process. Use a point source (like an LED), close the shutter or unscrew the elements so that you're looking at only one element, and then slowly tilt the lens. The number of reflections tells you the number of glass interfaces, the relative intensity tells you the type of interface (air-glass or glass-glass), the direction the reflections move when you tilt the lens tells you the direction of the curvature of that interface (convex or concave), and the speed with which the reflections tells you a bit about the degree of curvature of that interface (i.e., the glass-glass interface on the middle and inner cemented lens elements of a Dagor are unusually steeply curved, so that reflection moves rapidly as you tilt the lens).

And sometimes one of the interfaces is so nearly flat that you have to position the light source just right to see the reflection (which is what I imagine happened in this picture). Assuming so, and seeing that the 7 reflections visible in your pic are all closely grouped (= shallow curves for all interfaces), and making an assumption that a 610 f9 barrel lens is likely a process lens, it's probably the classic 4-element Artar-type construction IMO. But checking the front and rear element separately would be a big help.

With a name like Schneider it must be true ...

Yes I'm sure you're tired of hearing that... I said it anyway

Thanks!