What is the 35mm focal length equivalent of a 65mm medium format lens, 6x7 to be specific. Isn't it approximately half? What is the factor? Thanks, Greg

-- Greg (gjaugie@home.com), May 31, 2000

Answers

It depends if you're talking about Horizontal angle-of-view, Diagonal aov, or vertical aov. Manufacturers like to give diagonal aov because it makes their lenses sound wider than they really are. Users, on the other hand, very rarely hold their cameras on the tilt to get all the subject in. Hardly anyone is interested in vertical aov to the best of my knowledge.

So, to answer your question, the equivalent on 35mm is either 33mm (56 degrees Horizontal AOV), or 30.5mm (71 degrees Diagonal AOV), and the corresponding factors are either 36/70 (horizontal) or 43/92 (diagonal). Didn't you guys do any geometry at school? :^)

-- Pete Andrews (p.l.andrews@bham.ac.uk), June 01, 2000.

That was trigonometry, not geometry, when I was in school.

-- Bill Mitchell (bmitch@home.com), June 01, 2000.

Michael K. Davis has a nifty calculator for comparing focal lenghts:

http://www.smu.edu/~rmonagha/mf/lenses3.html

-- Chris Ellinger (ellinge@umich.edu), June 02, 2000.

Kodak Professional Photoguide, Sixth Edition, P. 42: a small analog chart (nomograph), but looks to be close to 33 deg.

-- Paul Harris (pharris@neosoft.com), June 02, 2000.

To Bill Mitchell,

Trigonometry is a part of geometry, when I last went to school. From the Greek: trigonom which means triangle and metron which means measure

To Greg,

You will have to calculate first the ratio of the diagonal of the 35 mm format and the diagonal the 6x7 format. Then apply that to whatever horizontal/vertical angle to are comparing in the two formats. You will have to have a rudimentary knowledge of trigonometry to accomplish that. And you cannot always trust the magazine's comparisons.

Good luck

Wladimir

-- wladimir schweigert (sgert@golden.net), June 06, 2000.

Hi Wladimir. When I was in school, Euclid was still in the first edition scroll. No doubt there have been some corrections since then. Regards, Bill.

-- Bill Mitchell (bmitch@home.com), June 06, 2000.