Fujinon L 420 on 400mm of bellows

Hi, i finaly paid for my 7x17. It is wide angle non folding design with 400mm bellows. I already have beauty 355mm lens for it.
But I was curios what is the longest lens I can mount.
Fujinon 420mm L came to mind.
I checked the pdf and found following data
Distance from flange to rear end of the lens 30mm
Flange focal distance 400mm

Does it mean that with 3cm top hat lens board
I will have 3cm of focus range?

If your bellows extend up to 400mm, presumably you would have a little bit of focus range due to the thickness of the standards and the 5mm distance into the film holder. An extended lens board should enable you to focus closer.

thinkbrown said:

An extended lens board should enable you to focus closer.

Click to expand...

...but not by a whole lot. I.e. landscapes, OK. Portraits & still life, nope.

If the camera has say 20mm of standard depth and you add a 30mm extension on that 50mm of focus range should allow for focusing as close as 3.6 6.3 meters according to the math. Not exactly a closeup but closed than I'd expected tbh

(Edit: I can't type)

Hanging almost a kilogram of weight on the front with a top hat board? How sturdy is the camera?

With a 2" top-hat you could do a lot. That's up to you to decide if it's enough, and as mentioned, that 420mm is a heavy mother. I use a Fujinon T 600mm on my Toko (NOT Toyo) 4x5 field camera -- which has 360mm of extension. The 600mm is large, but not too heavy, and only needs 385mm of extension, so a 2" top-hat works fine for me. Depending on your camera, a top-hat might work for you too, but there might be some logistical obstacles -- like getting the rear element to fit inside the top-hat without vignetting.

But there are other alternatives, like the Fujinon T 400mm (260mm of extension), but I doubt that the T lenses will cover your film. Anyway, here is their complete rundown of lenses with IC size and FFL:

http://www.subclub.org/fujinon/