=====Cooke Varotal 20-100mm T3.1 ===== 
{{ :lens:20240912_130733.jpg?direct&400|}}
==== Summary ====
==== Tech Specs ====
| Manufacturer    |Cooke|
| Series          |Varotal|
| Model           |-|
| Focal Length    |20-100mm|
| Max Aperture    |T3.1|
| Min Aperture    |T22|
| Format          |-|
| Image Circle    |-|
| Minimum Focus   |28 in.|
| Focus Rotation  |-|
| Iris Blades     |-|
| Optical Design  |-|
| Squeeze         |none|
| Front Diameter  |144mm|
| Filter Thread   |-|
| Focus/Zoom Rod  |-|
| Native Mount    |PL|
| Data Protocol   |-|
| Length          |12.6 in.|
| Weight          |5216g|
| Body Telescope  |none|
| Body Material   |Aluminum|
| Focus Drive     |Manual|
| Iris Drive      |Manual|
| Zoom Drive      |Manual|
==== History ====
Country of Origin: - \\
Release Date: 1971 \\
Launch Price: - \\
Design Revisions:\\

==== Service ====
<nodisp 8>
Known Issues: \\
<wrap note>1. when 144mm front mask (held on with set screws) is removed, the OD of the lens is now 139mm but the front element is exposed to damage. use caution if removed! There may be some variations in some models.\\
2.  The Cooke/Techo 20-100 had an option to convert it to an 18-90mm Techno performed by Henri Choscicki in Rome at Technovision. He took a stock Cooke 20-100mm T3.1 and added an extra front and rear element to make it wider and faster. If either conversion element is missing, it might have little difference from the original 20-100mm lens. </wrap>\\
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Service Manual: [[staff:servicedb:cooke20-100|Disassembly/Re-assembly]] \\
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Full CLA: **14 hrs.**\\
<wrap note>Enter relevant notes here</wrap>\\
Re-collimate: **2 hrs.**\\					
re-center front optics: ** full CLA + 3 hrs.**\\	
<wrap note>+ 1 hour for each 3 rollers</wrap>\\
C/A front optics: **5-7 hrs.**\\
<wrap note>moving focus group can have powdered contamination inside assembly due to 2 element edges sitting directly on each other. assembly may have lock ring difficult to access (BE CAREFUL! do not chip exposed element) or clamps holding optics into place.</wrap>\\
Zoom Spring: **$20**
<wrap note>(sits under teflon follower block) straight (not conical). old ones (like the ones we have in stock) were weak and would allow the teflon block to get pushed and and shift optics. At some point a stronger spring was made available.</wrap>\\
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**Accessories:** \\
<wrap note>Lens support: ID: 3.918", no integrated motor bracket, #38209039</wrap>\\
</nodisp>

==== Notes ====
==== Media ====