There's this guy…

Joanna Carter

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… in one of the Facebook LF pages I occasionally drop in on, who has stumbled across something called a Garutso lens balancer, usually used for movie lenses, to increase depth of field, but that he thinks could be made to work for LF.

For some reason, he feels movements would not do because he seems to want to shoot people with a wide open aperture, in limited light

Personally, I think he's barking up a non-existent tree but I was wondering if @Ian Grant had any ideas or thoughts I could pass on to him?
 

Ian Grant

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Having seen Mr Stephe R Garutso's 1946 Patent it appears rather backward and out-dated. Back then few plasmat lenses were used because they needed coating due to the large number of air/glass surfaces, and it was new technology.

The major issue just after WWII was most lenses were poorly corrected for wider apertures. Now all LF lens designs are optimised for f22 and at a push f16 and some designs are better at wider apertures than others. Poorest is the original Cooke Triplet, the modern Rodenstock Geronar is a MC version, next is the Tessar & type (Xenar etc), and finally the Plasmats -Symmars, Sironars and equivalents. There's about a stop difference in sharpness between each, a Plasmat at f8 is roughly as sharp as Tessar at f11 and a Cooke Triplet at f16.

I think the mistake Joanne is the poster is mistaking lens correction and overall improvents in sharpness with increase DOF, as is the Garutso Patent. We live in different times today Garutso has been surpassed by the aspheric lens element which allow amazing corrections particularly with zoom lenses.

It's unlikely we'll see any new LF lenses for some time, first we need a new supply of shutters, my fasest LF lenses are a 135mm CZJ f3.5 Tesaar and an 6" f3.5 Dallmeyer Press.

I'd actually suggest the poster goes and looks how those lenses were used, after all there was also the 165mm f2.8 Tessar and there's amazing images made with these lenses, suggest he buys Paris by Night, Brassai. Then tell me which tree he's barking up and my Dalmation will go cock his leg there :D

It's not the lens it's the person using it . . . . . . . . .

Ian
 

Collas

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You can still get a brand new Cooke lens from Robert White, though the only one in stock is the 10 x 8 format Cooke Series XVa Triple Convertible Large Format Lens - Copal 3s Shutter which is a snip at £3999. Which is still cheaper than the Cooke PS945 229/f4.5 Large Format Soft Focus Lens - Copal 3s Shutter.

Nick
 

Ian Grant

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I have a few TTH Cooke lenses, came with cameras except one for around £15. At £3999 for a XVa I think they'll make to order, must test my Turner Reich Triple convertible came free with a shutter :D

Going back to Joanne's question, I can't see how you can make a lens of the same FLhave more DOF han another at a wide aperture. Overall sharpness yes.

Ian
 

David M

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It may not be relevant in this case, but I recall hearing of a photographer who said that cheaper lenses had "bags of depth of field" and expensive ones didn't. I believe that this was a reporter from the good old days, using something like a Speed Graphic. I have no information on the actual lens. As the inferior lenses had no really sharp detail, the out-of-focus blur was not made evident by comparison.
 

Ian Grant

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There may be some wisdom in that story David, if we think of of pre-WWII cheap LF lenses they were Rapid rectilinears and later Dialytes, mid range would be Tessar and type, and top end Dagor's, Protars and a few early plasmats.

The Dialytes would have the best correction and overall sharpness particularly at wider apertures but their 6 internal air/glass surfaces mean there's a loss of contrast very noticeable compared to a Rapid Rectilinear or Dagor/Protar with only 2 internal air/glass surfaces. An uncoated Dagor or Protar has about the same contrast as a modern coated (or MC) Plasmat, an uncoated Plasmat suffers contrast drop like the Dialytes, a Tessar is inbetween.

After WWII the Dialyte design largely disappeared, Rodenstock coated a few Eurynars, and Kodak sold their 8"/203mm f7.7 Anastigmat coated as the 203mm f7.7 Ektar, coating these lenses made a huge improvement in contrast. The Dialyte design was also used for Process lenses, usually slow f9 maximum apertures.

It would be interesting to test a 210mm f6.8 Geronar (Cooke Triplet), 203mm f7,7 Ektar (Dialyte), 210 f6.3 Osaka Commercial (Tessar), and 210mm f5.6 Symmar S (Plasmat) to see if there was any apparent difference in DOF at say f8, all are coated lenses.

Ian
 

David M

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Yes.
Being a bit more academic, Depth of Field is the product of aperture and the acceptable circle of confusion. Increasing the Circle pf Confusion automatically delivers a bigger number for DoF.
 

Ian Grant

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Yes.
Being a bit more academic, Depth of Field is the product of aperture and the acceptable circle of confusion. Increasing the Circle pf Confusion automatically delivers a bigger number for DoF.
And a less sharp image particularly when enlarged. I remember some years ago calculating my own DOF tables for my LF lenses because I found the COC critera use unrealistic, I still have the tables in a notebook but have never referred to them. I think the first time I'd done something similar was for my 80mm f2.8 Sekor lens on a Mamiya C33 which I was using to shoot a jewellery catalogue 1976/7 DOF and sharpness was critical.

Ian
 

David M

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We have been barking up the wrong tree.
The Garutso lens is a correction lens with a hole in it, but it seems to have been built into the lens rather than added like a filter.
We should remember that this is for 35mm moving pictures where the image is inherently very poor and apparent sharpness is achieved by overlaying successive images.
A typical on-screen picture might be an actor in the centre of the screen with some kind of scenery around, which would naturally be out of focus. The Garutso lens would leave the central area focused by the primary lens and the periphery would be re-focused by the Garutso annular lens.
I think we can see that on a large format image, the difference between the two areas of focus might be visible as a circular patch.
Here's a reference to an article in Popular Mechanics:


There's a lot of other fascinating stuff in there too.
 
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Ian Grant

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I've read the complete Garutso Patents, all three and the illustrations are nothing like the magazine article. Firts the lenses are convex with the centre removed and the inner edges blackened or you'd have severe contrast reduction but this will also act as a slight diaphragm on the edges of the image and the FL of the edges of the image will differ to the centre so not a flat field of focus.

Could this be done in an easier way, very likely. We are looking at the exact opposite of a flat field lens, a typical LF lens (of 35mm/MF) is not fully corrected, in simple terms with no correction if we focus at full aperture at20 ft in the centre, then objects at the edges of the frame at 20ft are sharp so a curved field. In practice our lenses fall in between as they have some correction.

Garutso however wants objects in the centre which are closer to be camera to be sharp at or near full aperture, and then the plane of focus to shift backwards as we progress to the edges of the frame. This gives the illusion of greater DOF. but there must be some costs in terms of overall sharpness.

Ian
 

David M

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Yes indeed. I did suspect that the Popular Mechanics article might be a little bit (ahem!) popular. Good enough for this bear of very small brain. The result might be a stepped field rather than a curved one, but this is a trivial point.

A small but irrelevant footnote: Although PM is published in Chicago, in 1950 they can still spell doughnut properly.
 
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