Grunlach Hyperion, difference between

**erian** · 16-Jun-2020, 07:15

The https://www.antiquecameras.net/softfocuslenses3.html lists 6 different Gundlach Hyperion lens sizes.

The two biggest ones are Nr 5 that can be combined into sizes 14", 20" and 36" and Nr 7 that can be combined into 18", 36" and surprisingly again 36".

Can somebody explain this? Why should somebody want to have Nr 7 instead of Nr 5? What were the advantages?

**Mark Sawyer** · 16-Jun-2020, 10:02

On the No. 5, it's a triple convertible, a 20" and a 36" that combine to give a 14", The No. 7 is a double convertible, with two 36" elements that combine to give 18". They could have also offered a double convertible with two 20" elements that combine for a 10". Guess it was an easy option to offer. The only advantage would be for someone who wanted an 18" but not a 14" or 20". The 14" configuration would not cover 11x14, but not the 18" would.

What I find really odd is that both use the 36" at the rear, but have different barrel/flange diameters...

BTW, adding the two elements' focal length and dividing by four gives the total focal length, or at least close enough.

**erian** · 16-Jun-2020, 12:55

Originally Posted by Mark Sawyer

On the No. 5, it's a triple convertible, a 20" and a 36" that combine to give a 14", The No. 7 is a double convertible, with two 36" elements that combine to give 18". They could have also offered a double convertible with two 20" elements that combine for a 10". Guess it was an easy option to offer. The only advantage would be for someone who wanted an 18" but not a 14" or 20". The 14" configuration would not cover 11x14, but not the 18" would.

What I find really odd is that both use the 36" at the rear, but have different barrel/flange diameters...

BTW, adding the two elements' focal length and dividing by four gives the total focal length, or at least close enough.

Thanks! Would that mean that these lenses are then also optically different? Is the coverage and the maximum aperture of them the same @36"?

**Mark Sawyer** · 16-Jun-2020, 15:08

Originally Posted by erian

Thanks! Would that mean that these lenses are then also optically different? Is the coverage and the maximum aperture of them the same @36"?

I would guess almost certainly yes, all the 36" elements are the same, as symmetry solves a lot of design issues. And all the single cells were 2-elements designed to work alone or in combinations. That's a lot in common to come up with two separate designs for. But not knowing that lens well, there's always the off-chance they did something weird. Maybe someone else who has the lens will chime in.

jp · 16-Jun-2020, 17:36

I have a Gundlach Hyperion 9" triple convertible, and have never taken it apart. I have never even moved the f stop further than one stop from open. I just use it and don't play with it. I would not expect it to work the same. It has a different aperture scale for the different focal lengths... Remember aperture is basically focal length divided by lens objective.