'Front cell' vs 'unit' focussing

[Dralowid]

(I guess this is mainly relevant to older folders and later fixed lens cameras. My interest here is in folders, Cero Dollina, Welta, Balda etc, lenses, Zeiss, Senheil, Schneider)

When looking at 35mm folders it seems there was a significant price difference at the time between cameras that had front cell focussing and those where the whole lens moved.

For mechanical reasons all the 35mm range finder folders I have found are unit focussing.

In reality, with comparable lenses, do you think it make that much difference to the end result?

Michael

 

[sevo]

Unit focusing means 1cm of movement for a 100mm lens that goes to 1m close focus - i.e. (assuming 50-75% overlap) more helicoid than you could collapse into folder shape. So a unit focusing folder needs a (complex and expensive) collapsible mechanism that moves the front standard while keeping parallel to the film plane. You can cover the same range with barely 2mm front cell movement on a triplet derived lens - which can be done with a plain thread, at a fraction of the cost.

Front cell focusing changes the focal length of the lens - and as the front cell is no achromat, this does affect the lens correction noticeably (a issue of the complexity feasible in pre computer days - modern internally focused lenses, which shift fully corrected groups for the same effect and purpose, often outperform their unit-focusing equivalents). At a designed sweet spot of f/11-16, this does not matter - but if you intend to shoot your folder wide open, get a unit-focusing one or live with some additional softness outside the range the makers optimized it for.

 

[Dralowid]

Yes it is easy to see the complexity when one compares Weltix with and without unit focussing. Of course the complexity increases still further with addition of a coupled rangefinder either focussed at the lens, Weltini, or on the body, Certo Dollina.

Taking your advice, for my next foray into old cameras I will try the Welta Ic which although without rangefinder has a unit focussing Tessar and a larger viewfinder.

Thanks,

Michael

 

[Roger Hicks]

(I guess this is mainly relevant to older folders and later fixed lens cameras. My interest here is in folders, Cero Dollina, Welta, Balda etc, lenses, Zeiss, Senheil, Schneider)

When looking at 35mm folders it seems there was a significant price difference at the time between cameras that had front cell focussing and those where the whole lens moved.

For mechanical reasons all the 35mm range finder folders I have found are unit focussing.

In reality, with comparable lenses, do you think it make that much difference to the end result?

Michael

Dear Michael,

In my experience, yes. Especially wide open.

Cheers,

R.

 

[FrankS]

Difference only at closer focusing distances and at wider apertures.

 

[Jack Conrad]

I've found that more complexity equates into more problems.
That's why I never date a woman with a bewilderingly complex selection of
of purses or shoes.
Cameras are no different. 🙂

 

[wallace]

The Super Ikontas have front cell focus. Why did Zeiss stay with that design? My Perkeo II has it too. These cameras belong to the best vintage folders for MF. On the other hand:
I love the design of the Welturs (with Tessar or Xenar) tried 3 of them but in comparison I found my Perkeo sharper.

wallace

 

[Ernst Dinkla]

In reality, with comparable lenses, do you think it make that much difference to the end result?

Michael

Almost ten years ago I asked a similar question and got some interesting replies:
http://photo.net/medium-format-photography-forum/004r7H


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