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Author Topic: Help needed understanding lens specs. Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 08-01-2005 01:57 PM                        I find it confusing trying to figure out what lens will give me what picture size. The Isco calculator is confusing and I also bought a slide rule ICECO and thats just as confusing. Some lens are marked in " while others in MM. Is there a general formula that works with all lens and easy to use. Thanks!!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-01-2005 02:04 PM                     the focal length of the lens can be expressed in either inchs or millimetres historically imperial lens sizes were made in 1/4" inch increments and metric sizes were in 5mm increments nowday all sizes are made the slide rule is very straight forwar set the throw first set the image size you want usualy the arrow on top is image heigth with the various formats widths below Then red off the lens size for the format in question (on most that is expressed as apperture heigth)  |  IP: Logged Aaron Sisemore Flaming Ribs beat Reeses Peanut Butter Cups any day! Posts: 3061 From: Rockwall TX USA Registered: Sep 1999 posted 08-01-2005 02:31 PM                     Use the Bell Cinema lens calculator, its VERY easy to use compared to the ISCO and Schneider software suites. You can get it right here at Film-Tech!! -Aaron  |  IP: Logged Ed Inman Expert Film Handler Posts: 103 From: Jackson, Mississippi USA Registered: Jul 2004 posted 08-01-2005 03:42 PM                        For flat prints: 75mm equals 2.95 inches (approx. a traditional 3" lens) 100mm equals 3.94 inches (approx. a traditional 4") 125mm equals 4.94 inches (approx. a traditional 5") 150mm equals 5.91 inches (approx. a traditional 6") A full mm to inches conversion chart is available in the downloadable www.iceco.com catalog. Ed  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 08-01-2005 04:21 PM                     1 inch = 25.4mm.....not that hard  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-01-2005 04:21 PM                     Ed said quote: For flat prints: Conversion applies to any lens not format specific  |  IP: Logged Alan Gouger Jedi Master Film Handler Posts: 501 From: Bradenton, FL, USA Registered: Jul 2000 posted 08-02-2005 09:03 AM                        Aaron Thanks for the calc. Perfect. Gordon With your instructions I was also able to figure out the slide rule and compared the results with the Bell Cinema lens calculator to confirm I was correct. Richard thanks for the conversion. Thanks everyone Im all set  |  IP: Logged

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