*Improved* Home-Brew Graflex RECESSED Lensboard...

[Scott --]

Hi, everyone -

Well, after my last attempt at a lensboard (http://www.largeformatphotography.info/forum/showthread.php?t=24287) worked, but lost me infinity focus with the Raptar 90/6.8 I've been trying out, I decided to make a recessed lensboard. The whole ordeal is chronicled over to nelsonfoto.com (http://nelsonfoto.com/v/showthread.php?t=9478) (which is, by the way, a really nice forum with lots of great people, for anyone who hasn't been there yet). But, in a nutshell, here 'tis:
http://i80.photobucket.com/albums/j185/bliorg/IMG_1685.jpg

http://i80.photobucket.com/albums/j185/bliorg/IMG_1686.jpg

The tub is a maple butt-jointed affair, painted on the outside with semi-flat paint (thought it was flat...) and flocked on the inside with SuedeTex black flocking (http://woodcraft.com/family.aspx?familyid=288). The front board is another piece of cherry. The whole thing nets me about 4 cm depth, which gets me infinity back when I drop the bed.

Film's on its way; I'll be testing this thing out next week. Wish me luck!
Scott

[Ash]

Good luck!!

[Gene McCluney]

This is very puzzling to me. I have a Super Graphic just like yours. I have a Graflex Optar 90mm lens that came with it. It focuses on infinity well out onto the rail, and does not need to have the bed dropped unless I am shooting a vertical shot. In your photos you show your Super Graphic with two sets of infinity stops. My 90mm Optar works with the first set of infinity stops. There is no doubt that I am getting a 90mm field of view. No doubt at all. I am truly puzzled as to why your Raptar requires such a radical difference in front standard position. The only lens I have that requires leaving the standard on the internal rail is a 65mm Super-Angulon, but it is in a helical focusing mount...so I can do rough focus by just sliding the standard backward and forward, then locking it down, then fine-tune the focus with the focusing mount on the lens. Of course the 65mm requires that the front rail be dropped even for horizontal shots.

[Scott --]

Gene, I wish I knew what the deal was. I've gotten several emails from people saying the same thing as you. Unless I'm doing something seriously backwards (always possible, often probable), it just focuses way back on the rails.

This picture is the 90/6.8 Raptar (mounted on a Super board) focused at infinity:
http://i80.photobucket.com/albums/j185/bliorg/IMG_1665.jpg

It's on the bed rails at this point, but just barely. Predicatably, it gave results like this:
http://i80.photobucket.com/albums/j185/bliorg/crop234.jpg

Dropping the bed opened the gap between the inner and bed rails enough that, to get infinity focus, the standard would have to stradle the two sets of rails, right in the gap. Which is why I went through this whole recessed board exercise.

Not sure why it focuses where it does. It's sharp enough when focused, so I don't think there's a reversed element anywhere, but anything's possible.

BTW, the first set of stops on the bed are for my Optar 135/4.7.

Scott

[Ash]

that's so weird. I kinda like the camera bed in the pictures, but i'm sure it would be very frustrating otherwise ;)

[Gene McCluney]

The photo you posted above showing the bed rails in the photo is exactly the view I get with my 90mm Optar when photographing a vertical without dropping the bed, but my lens is sitting firmly on the focusing part of the rails. Simple matter to tilt the bed, then raise and correct the tilt of the lens with the adjustments on the front standard. The 90mm Graflex Optar is a small lens just like the Raptar, rather than the newer Super-Angulon style of WA. Mounted on a black lensboard just like your Raptar was, it could be mistaken for it. Probably my first set of infinity stops are further back on the rail, but rest assured the 90mm Optar functions entirely on the focusing part of the rail. It is indeed a puzzle.

[Gene McCluney]

You know, I was just wondering....perhaps the 90mm Graflex Optar was designed specifically for the Graphic line of cameras, and the Raptar was not. This might explain the better focusing position (rail wise) of the Optar.

[Brian C. Miller]

The Optar could have a retrofocus design, thus allowing it to be used further out on the bed.

[Scott --]

FWIW, this page (http://www.cameraeccentric.com/html/info/wollensakcatd/design.html) shows the Raptar wide angle f/6.8 lens design. Not sure how to tell if it's retrofocus (doubt it, considering the trouble I'm having...).
,

[jnantz]

hi scott

looks like a nice lensboard you made there!
lucky for me, i have a pacemaker speed graphic and my
raptar used to sleep on a flat lensboard. like you, i always
dropped the bed when i used it ( but the front standard remained in
the box of the camera ).

[Brian C. Miller]

The Wikipedia retrofocus design (http://en.wikipedia.org/wiki/Wide-angle_lens) page has an illustration of the retrofocus design. An element is added in front of the main group to provide a wider view angle. Your lens is definitely a normal short-focus design.

[Scott --]

Interesting link, Brina. Thanks.