Originally Posted by willwilson
I guess he is referring to the exacting requirement for plane parallelism of the front & rear standards to operate an ultrawide angle lens: any minor tilt, not visible on a field camera, will amplify the error margin for focussing. Detents, or zero-neutral positions at 0 +/- tilt of standards, shifts and axis.
I used to use Greg's set up on the Chamonix whole plate format [6 1/2 x 8 1/2 inch] with the Schneider Super Angulon XL 90/5.6 lens. With front bed tilt, moving the front rail out of the way, it is operable albeit challenging. This is the widest lens I've been able to use on the whole plate format. The ground glass of the Chamonix is average; neither bright nor outstanding but serviceable. Moved on now to use the Argentum whole plate set up with the 90mm XL lens and it is less troublesome since the front standard operates without the rail intrusion of the Chamonix. The screen seems to be just higher grade glass and easier to focus. That's just my perception although at 90/5.6, a degree of extreme focussing diligence is the norm.
On 4x5 format, the Beattie Intenscreen; the Wista or Ebony bright screens only permit a central area of focus before the whole ground glass glares reflection. This is one reason why using a helicoid focussing on 4x5 lenses like the Schneider Super Angulon 47mm XL f5.6 - particularly with a centre filter - is more deft and smooth - on a Silvestri Hermes which has a rigid solid aluminium billeted chassis with exact plane parallelism to the lens axis. That is - no rear movements: any 4x5 inch camera with a fixed rigid back and no movements like the L shaped Ebony 45S, Argentum Architectural 4x5 or Titan Walker XL have a market for ultra wide angles. Their screens are all very different. The Ebony is the brightest which is also one of the hardest to focus. A 75mm Super Angulon f5.6 is pretty easy to focus - and a Grandagon 75mm f4.5 even more impeccably so. Perhaps the challenge is not the lens ... a 6x Silvestri loupe (pretty hard to get a hold of now) just offers that extra snap over a 4x with the cripplingly tight 8x loupe.
Having had a Chamonix F type whole plate camera, the groundglass is not the last word either, so you have a few options, including inserting a fresnel on the ground glass too. Hope you can work through it. It's rewarding an ultrawide angle set up can be configured. It's a specialist field and most of us ultra wide angle shooters don't conform to the algorithms of standard LF photography
Kind regards
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