Anamorphic Lenses and Format Compression Ratios
REMARK: This text was originally written [with many thanks to the Widescreen Association, AWA -The Australian Widescreen Association, and the AWS - American Widescreen Society, and to Tony Shapps aka Mr. Widescreen...of the Widescreen Centre] by Mr. Martin W. Baumgarten. However some minor updates had been made, so the text now differs from the one released by Mr. Baumgarten.
Anamorphic Lenses and Format Compression Ratios[edit]
While not all inclusive, and perhaps some errors which sharp-eyed readers will point out...or add useful information of their own....it is a good starting point. Many Widescreeners have used virtually every conceivable combination of anamorphic lens and camera and projector combination. Simpler and older lenses that are not multicoated or coated at all....do worse for camera use than a better lens of course. As long as the projection intended lens can focus to infinity, it can almost always be used for filming as well as projection. The catch is how does the lens mate to a given camera lens....what focal length is the cut-off at, and can you live with the degree of cut-off to film at that minimum focal length.
The camera and projector A-lens adapters differ significantly and can't normally be used interchangeably. However.....the simple custom-mount once made by the Widescreen Centre, can be used on both with some simple ingenuity and also works well on slide projectors. Some of the lens brackets made for cameras are:
- Animex compendium type lens bracket with many x/y/z adjustments
- Custom-Mount
- Custom-Mount Deluxe (has rear camera lens threading)
- Rechter lens brackets
- Spondon Film Services brackets.
- BTB Mount (back-to-back A-lens mounts)
- Iscorama System (3-part 35mm system/adapter)
- No. 95 Mount (projector only mount for Eumig 8mm & similar) and some others.
The letter designations refer to the lens' size and which projection lenses in the industry it is intended to fit (varies also to the degree of 'throw' in a particular cinema). Some lenses are designed to work on both 16mm and 35mm projection equipment; yet will also work fine on 8mm, Super 8mm and 9.5mm projectors if you use custom brackets made to fit them or free standing adjustable A-lens holders. A free-standing unit for projection is great for home use as it allows ease of transferring the lens to any projector without any complications in setting it up. Since some lenses were designed for a longer projection throw....they usually have longer barrels. A long barrel isn't ideal for camera work...but if you can live with the various limitations, they can still be used. A lens such as the unique Iscorama 54...has a rear barrel diameter of 54mm and massive front optic diameter.....so much so...that it can be used with most large zoom lensed cameras throughout their entire zoom range. The lens makes for a weighty unit when combined with the camera and A-lens bracket....but for those wishing to film in the 2:1 aspect ratio using a 1.5x compression A-lens...this is the baby to do it.
I opted for the 2x format when I got into WIDESCREEN...since it is considered "Full-Scope" and offered the most variety for the money. Using a single lens, the KOWA 16-H, I can film in full CinemaScope and project with the same lens. Also...I can do still photography allowing for ultra widescreen 35mm slides in the 3:1 aspect ratio.....just breathtaking! And.....most theatrical releases in 8mm, Super 8mm and 16mm that are anamorphically compressed for these commercial release prints and digest films.....are done in the 2x compression ratio format. So....by buying one good lens....I got a lens that will give me 4 various uses. In fact...any good A-lens will give you back twice for your money...since you can use it for both photography and projection. There are some specialized still camera lenses and also a special enlarger lens for darkroom work so that still prints can be done from negatives or slides...but only in the 1.5x compression format. The KOWA 16-H (also known outside the USA as the 8-Z) is often referred to as the 'Kowa standard lens', and the KOWA 16-D is referred to as the 'Kowa-compact lens'.
This listing is certainly not all inclusive. However, the following will give the reader an informative representation of some lens names, their compression ratios, approximate light loss to be expected, and some other related factors. Anamorphic lenses can be used for achieving distorted photographic effects, but their main use is to expand the 'normal' vision of camera lenses and thus alter the aspect ratio to that of a WIDESCREEN format. Three main Widescreen formats exist, although there are various others; especially those used in optical printing machines to create an anamorphic release print of an already Widescreen format such as films shot in 65mm and then released on 35mm. With a variety of motion picture formats in existence, and their associated camera gate aspect ratios (which can vary again if filmed anamorphically), variable compression lenses are utilized in optical printing to enlarge or reduce a given format/gauge to another. These specialized lenses are then only used in laboratory conditions and are too unique and expensive for actual camera use. I will cover the lenses that are and have been used photographically in cinematography; some also can be and have been used for Widescreen still photography. Some of these lenses were primarily intended for projection use. However, since they will focus to infinity, they can also be employed for photographic use as well.
| LENS NAME | COMPRESSION RATIO | LIGHTLOSS (in F/Stops) | REMARKS |
|---|---|---|---|
| Beaulieu-Iscorama-Schneider | 1.5x | 1/4 | 10mm prime lens, focusing: 5ft - infinity |
| Bell & Howell | 2x | 1/3 | focusing: 5ft - infinity |
| Bolex/Moeller | 1.5x | 1/3 | focusing: 2m - infinity |
| Centascope | 1.5x | 1/4 | fixed focus |
| CentaVision | 2x | 1/3 | made by Isco, focusing |
| Cinepro | 2x | 1/3 | |
| Dyaliscope | 2x | 1/2 | |
| Delrama | 2x | 1&1/4 approx. | fixed focus |
| Delrama | 1.5x | 1&1/4 approx. | fixed focus |
| ElmoScope | 2x | 1/3 | |
| Expandascope | 2x | 1&1/4 | |
| Fantascope | 2x | 1/3 | |
| Filmorama | 2x | 1/3 | |
| Hexascope | 2x | 1/3 | |
| Hypergonar (CinemaScope) 16/35mm | 2x. | 1/2 | focusing |
| Hypergonar (CinemaScope) Large 16mm | 2x | 1/2 | fixed focus |
| Hypergonar (CinemaScope) Small 8mm | 1.75x | 1/2 | fixed focus |
| Ikonomorphot | 1.5x | 1/2 | |
| Iscorama 36 & 46 | 1.5x | 1/3 | |
| Iscorama (CentaScope) | 2x | 1/3 | |
| Iscorama 54 | 1.5x | 1/4 | |
| Iscorama SPA | 1.5x | 1/3 | slide-projector-adapter |
| Iscorama Widescreen-2000 | 1.5x | 1/3 | fixed focus |
| Kenko(scope) [also Cambron] | 1.75x | 1/4 | |
| KinoScope | 1.5x | 1/4 | fixed focus |
| KonicaScope | 1.5x | 1/3 | |
| Kowa (16H,8Z, etc) | 2x | 1/3 | focusing: 5ft - infinity |
| Kowa PA-35 (In-Flight) | 1.75x | 1/3 | focusing: 5ft - infinity |
| Magnascope (enlarger lens) | 1.5x | 1/3 | complete focusing |
| Petrascope | 1.5x | 1/4 | |
| Proskar | 2x | 1/3 | |
| Polestar | 2x | 1/3 | |
| Palamorphot | 1.5x | 1/4 | crude slide lock focus |
| Sankor 16-C | 2x | 1/3 | focusing: 5ft - infinity |
| Sankor 16-D | 2x | 1/3 | focusing: 5ft - infinity |
| Supa-60 | 1.5x | 1/3 | focusing |
| Sun A-Lens | 2x | 1/3 | focusing |
| Totalvision/Ruralscope | 2x | 1/3 | |
| Sankyoscope | 1.5x | 1/3 | fixed focus |
| VistaScope {8mm format} | 1.5x | 1&1/4 approx. | fixed focus |
| VistaScope {16mm format} | 1.5x | 1&1/4 approx. | fixed focus |
| Widescreen S-60 | 1.5x | 1/4 | fixed focus |
| Widescreen 2000 | 1.5x | 1/4 | fixed focus |
| YashicaScope | 1.5x | 1/3 | fixed focus |
The stated light-loss amounts are averages and actually are slightly more than measured at times; to err on the safe exposure side. If using a TTL metering system as is present in most modern cameras, then the meter will compensate for any light loss. This listing is to assist those that will use manual exposure cameras with separate hand held light meters, so these values can be factored in as compensation. Additional compensation is required for certain long zoom lenses on their telephoto end, and also for any filters that may be used.
Light-loss varies depending on how complex the A-lens is in its construction. Simple lenses are often of a monoblock design, or use just two single elements at either end. The simple two element design yields the least light loss of all, but is not corrected for astigmatism, curve-linear distortion and good colour correction as are the more complex lens designs. The Iscorama lenses (with the exception of their late 2x lens which is virtually identical to the Kowa 16-H but with actual rear camera filter threads to fit 49mm diameter and front filter threads) employ a unique focusing design. The prime lens behind it is set to infinity and only the anamorphic lens needs to be focused. However.....this method of focusing was only incorporated into their popular 1.5x lenses; as some of their very early ones require the common practice of both the prime and A-lens being set to the same distance setting for correct focusing (with some optical variations on certain camera lens & A-lens combinations). Some lenses such as the VistaScope and Delarama lenses (made by Delft in Holland) use a bent mirror and monoblock design which eats up just over 1-Stop of light. Also...due to the cement of the optics, often a slight tinting of the image might be noticed; but usually isn't objectionable unless there is severe discolouration in the lens unit itself.
KOWA lenses: These are quite popular and were also marketed under the name of Singer/Sankor, Bell & Howell, Elmo, and a few others. Since there is often confusion on these Kowa lenses...I'll go over them in a bit more detail below. Design variations exist to accommodate projection use on various projectors that they were intended to be used on. D.O.T. Industries in Rochester, New York, USA which was the official importer and dealer at one time, also sold a variety of specialized projection brackets for various anamorphic lenses. Although almost any anamorphic lens can be used for actual photography in filming (or some for still photography), there are various limitations as to lens size (diameter of main camera lens), zoom range utilization, focusing etc. This is based on camera lens & anamorphic lens (or A-lens as us Widescreeners refer to them as) combinations and compatibility. Also, note here that these lenses often have odd and non-camera compatible rear threading. That is because the threading was originally designed to be used with various adapters and as is to fit certain projection lenses on 16mm movie projectors.
To use these and many of the above listed lenses on a camera, it is important that you manufacture or purchase a special A-lens bracket which will secure the lens to the camera's tripod or movie light socket and hold it in position over the main camera lens. There were and are various brackets made depending on which lens you planned to use. IF using the ISCORAMA 1.5x lenses, and you have a camera lens whereby the front standard does or doesn't rotate....you could affix the lens directly to the camera lens for use. That is, again, because only the A-lens is focuses, so it doesn't lose it's correct orientation. The A-lens has to be orientated over the camera lens so that when viewed from the front, the A-lens optical oval appears in a perfect vertical stance. The A-lens is normally aligned visually thru the viewfinder, or aligned via a top marking on the lens.
The following are all 2x compression ratio lenses which will yield an approximate aspect ratio of 2.66:1 from the 'normal' 1.33:1 camera frame format. This compression ratio is also known as "fullscope" or "CinemaScope."
| Kowa 16-A | A mid-size lens with approximate 49mm rear flange diameter, and a long barrel length. |
|---|---|
| Kowa 16-D | A very small compact lens with 43mm rear flange diameter. |
| Kowa 16-C | A mid-size lens with a long rear flange with approx. 49mm diameter. |
| Kowa 16-F | A mid-size lens with a compact length at 5ft setting and a longer length at infinity setting with an approx. 52mm rear flange diameter. |
| Kowa 16-H | A mid-size popular lens with an approx. 52mm rear flange diameter. |
| Kowa 8-Z | Identical to the 16-H lens (this designation was used in Europe). |
| Kowa PA-35 | A large-size lens with approx. 54mm rear flange diameter. This lens is in the 1.75x compression ratio [yielding an average aspect ratio of 2.25:1 from the standard 1.33:1 camera frame format] |
Of the above Kowa 2x lenses....only the 16-H & 8-Z work the best since they have a very short length at their infinity setting, thus allowing minimal vignetting (referred to as 'cutoff' by Widescreeners) at the minimum allowable focal length. This minimum focal length varies depending whether you are using a small prime lens or a zoom lens. On the majority of Super 8mm cameras, there are zoom lenses. The more useful ones for WIDESCREEN filmmaking are those with zoom ratios of 6:1 or less, since their front optic diameter is closer to that of the rear A-lens flange diameter of 49mm on the Kowa lens.
For example...using a SANKYO XL-620 Supertronic camera, and the Kowa 16-H lens, my 'cutoff' or minimum usable focal length is in the 15mm to 17mm range. I have to give a variable range here...since it does change slightly depending on the distance focused as there is some lens extension on the camera lens to slightly affect this. However....a focal length of 15mm on a Super 8mm camera using a 2x anamorphic lens will yield an 'effective focal length' of 7.5mm in the horizontal plane. That is because the compression of the A-lens is only in the horizontal plane. Yet since the camera lens is actually set at 15mm, just about the 'normal' focal length for Super 8mm, there isn't any wide angle distortion present as would be if the camera lens were zoomed all the way to wide angle of 7.5mm filming 'flat'(without an A-lens).
If you try and use a Super 8mm camera with a zoom ratio of 8:1, then the 'cut-off' will most likely be at a longer focal length.....perhaps 25mm to 30mm. Although you won't have any wide angle capability.....this is still usable....since even at 30mm, the 'effective focal length' when using a 2x compression A-lens would be 15mm. And 15mm is considered near 'normal' for Super 8mm; whereby a normal perspective is achieved. If you use a 10:1 or 11.4:1 zoom lens camera such as a CHINON, ELMO or NIZO for exampled....the 'cut-off' point would be even at a longer focal length such as 40mm or thereabouts. Also, a large stepdown ring would have to be used to avoid having the A-lens come into physical contact with the front optic while in use. This still isn't a total loss, as I have often used the 16-H with a NIZO S-800 to achieve a CinemaScope image at times when I required a long telephoto magnification. To go even further....the A-lens could be used over a 135mm, 200mm or longer still camera lens mounted to a BEAULIEU interchangeable lens camera.
Most of this also applies to 16mm and Regular 8mm cine cameras, which have lenses with similar physical attributes to front optic diameter which would allow for a good or poor match-up to the A-lens you plan to use.
So, to go over projected image formats...the anticipated aspect ratios of the following main formats are:
- 1.5x from the 1.33:1 standard camera frame format = 2:1 aspect ratio projected
- 1.75x from the 1.33:1 standard camera frame format = 2.25:1 aspect ratio projected
- 2x from the 1.33:1 standard camera frame format = 2.66:1 aspect ratio projected
NOTE: The aspect ratio is stated for a matter of comparison....since not all projectors crop the images to the exact 1.33:1 camera ratio (nor all cameras for that matter), so upon projection thru an anamorphic lens the actual perceived image might be slightly less or slightly greater than these aspect ratios. And....the size of the screen and black masking or curtains used, would also slightly alter the projection aspect ratio enjoyed.
Some Specifications:
- KOWA 16-H (or 8-Z) lens
- Magnification (horizontal).....2x
- Distance Scale.................5ft to Infinity
- Rear Barrel Diameter...........52mm
- Length.........................84mm
- Net Weight.....................530 grams
- Filter thread..................none (must use add on Centafit {72mm} or similar)
- Rear Barrel Threading..........50mm
- Light-loss Absorption..........1/3 F-Stop or less
- KOWA 16-D (compact lens)
- Magnification (horizontal).....2x
- Distance Scale.................5ft to infinity
- Rear Barrel Diameter...........43mm
- Length.........................92.5mm
- Net Weight.....................290 grams
- Filter Thread..................none
- Rear Barrel Threading..........43mm
- Light-loss Absorption..........1/3 F-Stop or less
- ISCO CENTAVISION (sold by Widescreen Centre in England and Scoptimax in Germany)
- Magnification (horizontal).....2x
- Distance Scale.................5ft to infinity
- Rear Barrel Diameter...........52mm
- Length.........................87mm (at infinity setting, 81mm at 5ft setting)
- Net Weight.....................520 grams
- Filter Thread..................72mm
- Rear Barrel Threading..........49mm
- Light-loss Absorption..........1/3 Stop or less
- ISCORAMA-54
- Magnification (horizontal).....1.5x
- Distance Scale.................2m to infinity
- Rear Barrel Diameter...........78mm
- Rear Lens Element Diameter.....54mm
- Length.........................102.5mm (maximum)
- Net Weight.....................1000 grams
- Filter Thread..................95mm
- Rear Barrel Threading..........77mm
- Light-loss Absorption..........1/3 Stop or less
- ISCORAMA-42
- Magnification (horizontal).....1.5x
- Distance Scale.................2m to infinity
- Front outside diameter.........87mm
- Rear Barrel Diameter...........43mm(?)
- Rear Lens Element Diameter.....42mm
- Length.........................83mm (maximum)
- Net Weight.....................750 grams
- Filter Thread..................82mm
- Rear Barrel Threading..........62mm
- Light-loss Absorption..........1/3 Stop or less
- ISCORAMA-36
- Magnification (horizontal).....1.5x
- Distance Scale.................2m to infinity
- Front outside diameter.........76.2mm
- Rear Barrel Diameter...........52mm(?)
- Rear Lens Element Diameter.....36mm
- Length.........................73.9mm (maximum)
- Net Weight.....................400 grams
- Filter Thread..................72mm
- Rear Barrel Threading..........49mm
- Light-loss Absorption..........1/3 Stop or less
- ISCORAMA WIDESCREEN 2000
- Magnification (horizontal).....1.5x
- Distance Scale.................none (fixed focus range 6m-inf)
- Front outside diameter.........59mm
- Rear Barrel Diameter...........49mm
- Rear Lens Element Diameter.....36mm
- Length.........................50mm (maximum)
- Net Weight.....................225 grams
- Filter Thread..................none
- Rear Barrel Threading..........49mm(?)
- Light-loss Absorption..........1/3 Stop or less
- SANKOR 16C
- Magnification (horizontal).....2x
- Distance Scale.................5FT to infinity
- Front outside diameter.........63.5mm
- Rear Barrel Diameter...........43mm(?)
- Length.........................99mm (at Infinity setting)
- Net Weight.....................500 grams
- Filter Thread..................none
- Rear Barrel Threading..........42mm
- Light-loss Absorption..........1/3 Stop or less
- SANKOR 16D (aka JAN 16-D)
- Magnification (horizontal).....2x
- Distance Scale.................5ft to infinity
- Front outside diameter.........74mm
- Rear Barrel Diameter...........52mm
- Length.........................129mm (at Infinity setting)
- Net Weight.....................700 grams
- Filter Thread..................none
- Rear Barrel Threading..........50mm
- Light-loss Absorption..........1/3 Stop or less
I hope I've been able to provide some useful information here to those interested in anamorphic lenses for use in Super 8mm filmmaking. Brackets can be designed and made up by those able to do so, or ordered (after providing the precise measurements) from places such as: The WIDESCREEN-CENTRE and thru Les Rechter of the Australian Widescreen Association. Due to the decline in Widescreen interest and those willing to join organizations, suppliers of various lenses and brackets have shrunk down to less than a handful. Often you can get brackets for projectors since these are quite common from professional projection supply houses, but getting a lens bracket made to use on your specific camera might be more difficult. A little forethought and ingenuity is called for in most cases and those persistant enough to go ahead and also patient enough to wait to have a bracket made, will be able to embark on their WIDESCREEN adventure. Since necessity is the mother of invention, there are many possibilities that one can come up with using various step-up and step-down rings, old odd lens barrels and fittings striped from various lenses and devices.
