does it have to be a helicoid?

[dirkfletcher]

Hello again,
Here a 4x5 camera that I just finished. Its more or less a larger version of the 2x3 camera I built a while back. I wanted something lightweight and compact for occasional 'sheet film outings'. This camera uses the same 2x3 Graphic front end (third camera I've build using one of these) and the super lightweight composite rear standard made by Mike Walker for the Ilford TiTAN 4x5 pinhole.

 

[Dan Fromm]

Cute. But what's the point of the clip-on rangefinder? I see half of the donor Graphic's focusing scale, which isn't particularly useful. If complete it could be used with just one lens. I know, you can always focus on the GG.

 

[moto-uno]

And for something much less attractive ( cheap and simple can be attractive ? )

 

[Dan Fromm]

Cute. But how do you focus it?

 

[BMbikerider]

gunner, there is NOTHING as precise as a focusing helicoid because there is no opportunity for wobbling or mis-alignment. In fact, I have often wondered why enlargers do not generally employ one instead of rack and pinion. - David Lyga

There have been enlargers that do have a hellicoid focussing, although none are in production now. (as far as I know) The UK companies of Gamer and Wray had them (Gamer had several) Then of course several of the Leitz B&W enlargers had them, Followed by their last model, the V35 colour enlarger had one. Although this enlarger was was essentially auto focussing, the hellicoid was used to help set up the autofocussing point. It seems that hellicoid focussing was the construction used by high end, very good quality enlargers.

Possibly the reason for not having them now is down to current enlarging lens design, especially the ones with the illuminated apperture ring. Turn the focussing stage and the illiminated section goes out of sight. Another reason will undoubtably be cost. A rack and pinnion focussing stage will be cheaper to make and is almost as good. (but not as easy to use.)

Let the corporate accountants loose in the design department and it all goes to worms.

 

[MattKing]

Bellows focusing greatly expands the range of lens and negative carrier combinations you can use on an enlarger without having to swap out anything other than the lens and carrier (and light condenser or diffuser).

You probably could replace the bellows on my Omega D6 with helicoid focusing, but you would most likely need several different helicoids, depending on which lens and carrier you are using.

 

[dirkfletcher]

Cute. But what's the point of the clip-on rangefinder? I see half of the donor Graphic's focusing scale, which isn't particularly useful. If complete it could be used with just one lens. I know, you can always focus on the GG.

When I photographed the camera the ground glass back hadn't been made yet (Mike Walkers design used small plastic spring clips to hold a film holder in place) so I couldn't calibrate a focus scale. The back was completed this morning so I'll be adding a calibrated scale for the 125mm and a second scale for the 65mm.

Here is how the back turned out if you are interested.

 

[Dan Fromm]

Thanks for the reply.