New 75mm Hypergon Lens

[Mark J]

The foggy area is directional, so it's not just due to the spinner being shiny on the inside. Are you sure you have the correct split between with/without the spinner ?
Ok, also, does the arm that holds the spinner need blackening ?

[amansjeanphilippe]

Hello
optically speaking, bright spinner and mirror aperture are a problem...
Do tests sun on you six

J.Ph.

[Mark J]

Ok, also, does the arm that holds the spinner need blackening ?

I'll scratch that comment, the main arm for the spinner shouldn't be in the light path.
On your negative, is the centre of the lens axis central to the scene on the right, or is there an offset while you have that density test strip ?

[Mark Sawyer]

The foggy area is directional, so it's not just due to the spinner being shiny on the inside.

The light reflecting off the spinner is directional, though.

[Mark J]

Yes, good point - if for instance the sun was off to one side.

The easy way to de-bug this whole issue is to put the spinner in place, open the shutter, remove the ground glass panel and put your inside the rear of the camera looking for glints from the spider/spinner though the lens. A sunny day would be best.

[ic-racer]

The lens was centered on the 8x10 sheet. I did a second identical image with the same exposure sequence and the dark slide all the way out, but did not process that sheet yet.

[ic-racer]

Since the spinner is acting like a lens cap for the center of the field, it probably needs to be very close to the lens too.
This one looks to be almost touching.

[ic-racer]

The shiny pieces were painted flat black taking care not to get paint on the ball bearing:

[ic-racer]

To improve the function of the aperture waterhouse stop, I added a 0.1mm 'wavy-washer' to the assembly, then applied blue loctite to the screw.

Attachment 244797
Attachment 244798
Attachment 244799

[ic-racer]

Ready for more testing:
Attachment 244800