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Compensating for the Konvas shutter angle and anamorphic extenters?


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#1 James Steven Beverly

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Posted 25 February 2010 - 09:31 PM

I've JUST finished reading The Camera Assistant's Manual (A GREAT read BTW, learned a lot) and was reading a section in the back about stop compensation on adjustible shutter cameras. There was a chart there that got me to thinking. The book mentioned that MOST fixed angle cameras were set at 180 deg which I already knew BUT I found out some time back that the Konvas, UNLIKE most people believe, is NOT set at 180 deg but at something like 150 or 155 degs which a shutter set at 150 deg, by the book's chart, called for a I believe a 2 stop adjustment, MY question is in order to match footage shot on my KSR-1 with a 150 deg shutter angle to say my Kinor C of PII which both have a 180 deg shutter angle, would I need to make the stop compenstation and DOES the fact that the larger element size of the OCT-19 mount lenses when compared to the OCT-18 lenses make any difference as well?

ALSO a lomo 100 and 150 round front anamorphic is nothing more than a 75mm with an extention built in. Now I have a set of macro lenses that have bellows like still cameras along with tube style extenters to increase ther focal length designed to fit my Kinor PII or a Konvas 2M. WHY couldn't something similar be built to extent the focal length of the Lomo anamorphics, an OCT-19 mount tube extender with the OCT-19 locking ring camera mount at one end and the male end at the other in 1.5 x and 2 x lengths like what is done on some 16mm cameras? Yes, you would have to compensate for the focus marks on the lens barrel but there should be a formula for that. It's GOT to me significantly cheaper to have extenders fabricated than spending 2400 bucks on a 100 or 150mm round front IF you can even find one OR spending the same ammount to buy a 75mm and have it converted to a 100 or 150.

AND are square front anamorphics the same thing, the longer 100 and 150mm just extentions of the 75mm, in particular, the 2 piece anamorphic OCT-18 mount anamorphics that fit my KSR-1?

Edited by James Steven Beverly, 25 February 2010 - 09:32 PM.

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#2 Olex Kalynychenko

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Posted 26 February 2010 - 06:18 AM

Konvas-1, Konvas-1M, Konvas-2M cameras have shutter disk with fixed angle of 150 degree.
The russian book show time of exposing of film for different shutter disk angle.
At 24 fps
the cine camera with shutter disk 150 degree will have time of expsing of film 1/58 sec
with 180 degree 1/48 c
The difference between 1/48c and 1/58c = 17%
1/48 s = 0.0208333 sec
1/58 s = 0.0172414 sec
1 stop - the difference at 100 % , 17% = near 2/10
The many digital light meters have scale 1/10 stop

But, need check of technical information of light meter.
The light meter Seconik L758 cine have Shutter-angle settings from 1 to 10o in 1o increments, from 15o to 270o in 5o increments plus 12o,17o,22o,144o and 172o individual settings.

Seconik L358 have cine mattering with shutter-angle 180 degree.

As of me, from practical experience, +/- 2/10 stops do not important at real shooting.
The more high error can have adjusting of aperture control of lens.
The matter is that, the every lens have adjustable interaction between real size of aperture hole and aperture scale.

The every LOMO lens have " T " stop scale. The "T" stop scale individual for every type of optical block.
If you set of aperture scale on 5.6 of OST-19 or OST-18 or Arri Pl lenses, the negative must have similar density ( If the lenses had correct adjusted T stop scale ).



WHY couldn't something similar be built to extent the focal length of the Lomo anamorphics, an OCT-19 mount tube extender with the OCT-19.


The technique of focusing of spherical and anamoprhic lens on short distance different.
The spherical lens can be adjust on short distance by moving of one part of optical block or full optical block.
The anamoprhic lens have complex design and consist from spherical lens and front anamoprhic component.
The spherical lens adjust on infity and total focusing of lens make by moving of optical component before anamoprhic component.
That's why, focusing of anamoprhic lens on short distance can be with special close up attachmnet only and do not work with tube mount extenders.
We build of front close up attachmnet on 150 mm BAS lens and had very good result.

The russian Square anamoprhic lenses had special clouse up glass attachment for shooting with short distance.
The minimum distance of focusing of 35BAS-4-15, 50 mm have 1.5 m, but, have two additional distance scales with minimum distabnce of focusing 1.0 m ( greq scale ) and 0.5 m ( red scale ).
This is two additional scales use with front glass close up atatchmnets.

The similar attachment have Foton-A, front anamoprhic adapter of Foton zoom lens.
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#3 James Steven Beverly

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Posted 27 February 2010 - 07:24 PM

Konvas-1, Konvas-1M, Konvas-2M cameras have shutter disk with fixed angle of 150 degree.
The russian book show time of exposing of film for different shutter disk angle.
At 24 fps
the cine camera with shutter disk 150 degree will have time of expsing of film 1/58 sec
with 180 degree 1/48 c
The difference between 1/48c and 1/58c = 17%
1/48 s = 0.0208333 sec
1/58 s = 0.0172414 sec
1 stop - the difference at 100 % , 17% = near 2/10
The many digital light meters have scale 1/10 stop

But, need check of technical information of light meter.
The light meter Seconik L758 cine have Shutter-angle settings from 1 to 10o in 1o increments, from 15o to 270o in 5o increments plus 12o,17o,22o,144o and 172o individual settings.

Seconik L358 have cine mattering with shutter-angle 180 degree.

As of me, from practical experience, +/- 2/10 stops do not important at real shooting.
The more high error can have adjusting of aperture control of lens.
The matter is that, the every lens have adjustable interaction between real size of aperture hole and aperture scale.

The every LOMO lens have " T " stop scale. The "T" stop scale individual for every type of optical block.
If you set of aperture scale on 5.6 of OST-19 or OST-18 or Arri Pl lenses, the negative must have similar density ( If the lenses had correct adjusted T stop scale ).





The technique of focusing of spherical and anamoprhic lens on short distance different.
The spherical lens can be adjust on short distance by moving of one part of optical block or full optical block.
The anamoprhic lens have complex design and consist from spherical lens and front anamoprhic component.
The spherical lens adjust on infity and total focusing of lens make by moving of optical component before anamoprhic component.
That's why, focusing of anamoprhic lens on short distance can be with special close up attachmnet only and do not work with tube mount extenders.
We build of front close up attachmnet on 150 mm BAS lens and had very good result.

The russian Square anamoprhic lenses had special clouse up glass attachment for shooting with short distance.
The minimum distance of focusing of 35BAS-4-15, 50 mm have 1.5 m, but, have two additional distance scales with minimum distabnce of focusing 1.0 m ( greq scale ) and 0.5 m ( red scale ).
This is two additional scales use with front glass close up atatchmnets.

The similar attachment have Foton-A, front anamoprhic adapter of Foton zoom lens.


Thanks for the information, Olex. I wasn't sure what the book listed as the stop compensation so I quickly looked it up last night. The chart recommends a -1/3 stop for a 150 deg shutter angle, like you mentioned, not critical in most real world situations but maybe slightly significant if you're dealing with a critical matching situation.

I'm not sure if I'm understanding you on the idea of rabricating 1.5x and 2x extenders for the 75mm round frong Lomo anamorphic lens. Are you saying, this will not work because of the complicated optical block or would adding a pricision made extender in effect increase the focal length of the lens?
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#4 Olex Kalynychenko

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Posted 28 February 2010 - 02:11 PM

I'm not sure if I'm understanding you on the idea of rabricating 1.5x and 2x extenders for the 75mm round frong Lomo anamorphic lens. Are you saying, this will not work because of the complicated optical block or would adding a pricision made extender in effect increase the focal length of the lens?


If we told about additional rear optical extenders 1.5x and 2x, like optical extenders of zoom lens OPF-18, I do not test of this devices with prime anamoprhic lenses.
I hope, 1,5x, 2x optical extenders can work, need test.

But, if you think, to use of 1,5x and 2x rear optical extenders for diminution of minimum distance of focusing of lens, this is mistakenly.
The optical extenders cut of part of image only and do not change of disctance scale of lens.
The optical extender change of aperture scale of lens only.

I told about simply lens mount extenders, tube with camera lens mount from one side and lens mount from other side.
This is tubes will work with spherical lens, but, do not will work with anamorphic lenses.
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