Fixed focus 4x5 camera

[Degroto]

Bit by bit my camera comes together. It looks like crap (still). Sorry I don't have photo's yet. As good as I could I managed to get infinity in focus and subsequently have tried ever since to get a filmholder in the plane of focus :-) Just a bit more and then painting the insides black and go for a testride with the camera. Propably my second attempt will be one following all the advise I have gotten here :-). Will post some photo's soon though... to be continued...

[Degroto]

@Steve I use a 65mm super angulon wide angle lens. I decided to use the Sinar lens board because it is already on it and I don't have the proper tools to take it off.

[McGirton]

From where do I measure de focal lenght of the lens? From the plate where the lens is attached?

Hello from France!

This is a frequently asked question

What you want is to set the proper distance between the lens mount and the film.
Hence, to do this, the knowledge of the focal length is not really useful, as strange as it may seem!
What you need is a distance given by lens manufacturers, named "flange focal distance" or sometimes "Flange Focal Length" (e.g. in Fuji lenses documentation).
This is the distance between the back side of the shutter and the focal point. The focal point is where an image of a far-distant object is projected sharp.
Now in order to properly set your lens mount in front of your film holder, you have to take into account the film holder's depth, which is for modern film holders compliant with the ANSI standard
- 2" x 3" and 4" x 5" : 5.0 mm +- 180 microns (0.197" +-0.007")
- 5" x 7" : 5.8 +- 250 microns (0.228" + - 0.010")
- 8" x 10" : 6.6 mm +- 400 microns (0.260" + - 0.016")

If you already have a springback with ground glass, simply focus the image of a distant object, no computation is required.

And if you wish to fix-focus at the hyperfocal distance, instead of infinity, starting from the flange focal distance, you'll need to slightly increase the length between the lens and film by a small amount, to be easily computed according to your working f/number, focal length and sharpness criterion.

You can have a look at this article (in French) by Gilles Barbier who built a fix-focus camera for the 5x7" format.
http://www.galerie-photo.com/barbier-hybis-90.html
In this case, focal length was 90 mm, the sharpness criterion was 150 microns, the working aperture f/16, hence the offset required to focus at the hyperfocal distance instead of infinity was 3.3 mm.

I've seen your replies a couple of times in different threads regarding this question, so OP excuse me if I highjack this one for a question. If I want to set up a fix-focus camera with a 90mm Super-Angulon, I have a Flange Focal Distance of 99mm and a Back Focal Distance of 67mm. Do those numbers change ragarding the F Stop? If I wanted to have the image sharp at f8, would the distance of the lens to the film change at f22? Or is f16 / f22 just a more "comfortable" area for the setup. The 67mm BFD should stay the same, no matter the how the lens is stopped down, correct?

[Dan Fromm]

FFD at infinity is FFD at infinity is FFD at infinity ...

BFD at infinity is BFD at infinity is BFD at infinity ...

Both are independent of aperture.

When you set your camera up, focus the lens, don't rely on published FFD. Lenses as made rarely have the focal length engraved on them or the FFD published in the brochures. For best results, focus the lens or measure its FFD at infinity.

[McGirton]

Yes, first I will confirm the distance with my full plate camera, then with the one I am building. It's a custom 6x12 so no ground glass, but I am making one to confirm the focus. Thanks!

[Degroto]

McGirton: No problem as long as I learn something from it :-). I have decided to go back to the drawingboard. My experiment that I was working at was a hopeless disaster :-D. My next attempt will be a pinhole first. If the camera is nice and sturdy that leaves me time to figure out the focus issue. I decided to take apart the lens so I can make a camera the "same" size as a 4x5 filmholder. A lens wrench tool is underway. I have to figure out what I can use as the focus plan of the lens. Is that where the aperture is or somewhere else? Is it at the back of the shutter? So back to reading this thread once more for information. A couple of photos. At the moment held together by ducktape. That will change. Also the small peices of wood on the inside will be replaced for larger ones the will go all the way along the inside of the camera so the filmholder will rest on it completely. This is more for distance measuring and stuf. A tiny spot of glue to hold it in and yet easy to take it of again. Of course the home made pinhole will be attached to the outside.

[Jac@stafford.net]

I make simalars.

For point-n-shoot at ordinary subject distances focus is critical. Choose wisely according to your habit. A focusing mount is best and worth the investment.

Here is my 4x5" with 47mm ƒ5.6 Super Angulon in a focusing mount. (It also has a ground glass back.) My next version on the bench at the moment uses the 47mm XL for more even coverage. The depth of the body will have to be deeper via a spacer.



Hope this helps.

[Degroto]

Thanks. For some reason I am worried if the whole steup wil cover the whole negative. It will but still. Where did you get the screwthingy so you can attach the camera on a tripod? One for a decent price?

[Jac@stafford.net]

For some reason I am worried if the whole steup wil cover the whole negative. Where did you get the screwthingy so you can attach the camera on a tripod? One for a decent price?

Is 50-cents a decent price?

There a couple good options for either 1/4" or 3/8" mounting. For the camera shown below, the bottom piece is oak. I used a three prong T-nut inserted from the top, and recessed so that it is flush at the top. (I choose a T-nut with shallow teeth or grind them down a bit.)

Another approach that works when you have a blind hole (cannot work from the top-down) is to use a threaded insert like this one. I like this particular kind because of the long lead which fits snugly in the predrilled hole to guide installation properly. Use bar soap to lubricate the brass threads to ease the installation.

The back is often the finicky part. For this camera I used a *Jay Bender 4x5 back. For all the others I find a used Graflex universal. It makes life so much easier.

*Jay has retired, but sometimes you can find them.

[Havoc]

Bit like my try to make a pinhole for 4x5:

Used alu because I have some around. The large hole is made so that a Fuji SWD 75 can pass through but so far I only tried with a pinhole taped in place. To have a tripod screw I'm going to recover the mounting plate from a broken camera. Easy to find and a source for other pieces as well.

I should continue so it is ready for pinhole day.