Gundlach Achromatic Meniscus Portrait f6 16-1/4" f stops: 6, 8, 12, 16, 24?

[Tin Can]

I have a nice one in hand, I have read about it below,

http://www.largeformatphotography.info/forum/showthread.php?18733-16-1-2-Gundlach-Achromatic-Meniscus-Portrait-lens&p=170873&viewfull=1#post170873

http://www.largeformatphotography.info/forum/showthread.php?73394-Gundlach-Achromatic-Meniscus-has-a-Removable-iris&p=699038&viewfull=1#post699038

Galli Pics lost here. http://www.largeformatphotography.info/forum/showthread.php?27056-lt-warning-gt-Boring-BS-Soft-Focus-Pics-lt-warning-gt-Spencer-Portland-Achromatic-Meniscus!&p=255337&viewfull=1#post255337

and of course here, page way down http://www.antiquecameras.net/softfocuslenses2.html


The f stops are odd, is this some other system? It's marked f6, f8, f12, f16, f24. Any ideas about the stops?

And no the iris is not unscrewing for me. But I didn't try really hard.

I will be shooting it with same era glass plate later tonight.

[Jim Jones]

The progression of f stops is logical, starting from f/6 and decreasing the exposure one stop for each of the marked stops. Using traditional f/numbers is better if one is using DOF charts or exposure guidelines from film data. The system on the Gundlach may be better for the less technical photographer who prefers a consistent system starting with the maximum aperture of the lens instead of the familiar f/number series.

[Tin Can]

Thanks, Jim. It does look geometrical. I just never saw that progression before.

I am definitely the less technical photographer.