Question about lens boards, lens diameters, and spacers.

[TheAgeOfAnalog]

I've been using a Beseler 67SC for a few years, but have recently upgraded to a 45MX on a MCRX frame. The 45 came with a single lens board and a decent 50mm. I have two lenses, a 50mm and an 80mm and boards for my 67, which are much smaller. Obviously, I need more 4x4" lens boards for the 45, but can I use the lenses from the 67? The mount is a much smaller diameter. Also, I'm seeing 4x4" lens boards on eBay with either a stepped area around the mounting hole, or what looks like a spacer. What are those needed for?

[reddesert]

Measure the lenses' thread diameter. The standard is 39mm thread, but some older lenses (Schneider in particular?) have a 25mm or 32.5mm thread, and there are some really big lenses with a larger thread.

50mm will work for printing from 35mm, 80mm from 6x6, but you'll need a longer lens like 150mm to print from 4x5.

The 4x4 lensboards for 23C and 45 are the same. There are all sorts of slightly different shaped lens mounting areas. The ones with relief around the mount hole are to allow mounting a lens that has thread length too short to stick through the full board thickness. The ones with a spacer are to get more extension for a long focal length lens. The KHB Photografix site shows a bunch of these board types, although they don't have them all in stock.

[TheAgeOfAnalog]

Thanks for the quick response. Ok, so as long as the 4x4" board has the correct sized mounting hole for the lens in use, there's no issue with using the lens being smaller in diameter, for example, the 50mm f5.6 Beseler lens with 25mm thread versus my 50mm f2.8 Compur with 39mm thread?

Measure the lenses' thread diameter. The standard is 39mm thread, but some older lenses (Schneider in particular?) have a 25mm or 32.5mm thread, and there are some really big lenses with a larger thread.

50mm will work for printing from 35mm, 80mm from 6x6, but you'll need a longer lens like 150mm to print from 4x5.

The 4x4 lensboards for 23C and 45 are the same. There are all sorts of slightly different shaped lens mounting areas. The ones with relief around the mount hole are to allow mounting a lens that has thread length too short to stick through the full board thickness. The ones with a spacer are to get more extension for a long focal length lens. The KHB Photografix site shows a bunch of these board types, although they don't have them all in stock.