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Atracksler
22-Mar-2016, 17:04
Looking at a few old lenses, they are measured in inches, like 8.5" and 6.5". What would be an equivalent focal length in mm? They both look like wide angles, just wondering how wide...

Jac@stafford.net
22-Mar-2016, 17:10
The easy short-cut so you do not even need to know how to calculate is to use Google.
For example, type 12 inches in mm and the answer will pop up.

ryanmills
22-Mar-2016, 17:10
Its a silly thing but its obvious in a way you think its wrong at first. You can convert it from inches to mm to get the same size but they tend to get rounded. For example 300mm is a 12" or and 8.5" would be 210mm, etc

koh303
22-Mar-2016, 17:17
Wow, its amazing what you can find on google these days.

vinny
22-Mar-2016, 17:32
Let me google that for you.........

Two23
22-Mar-2016, 17:34
I just use the quick approximation of 1 inch is 25mm.


Kent in SD

Oren Grad
22-Mar-2016, 17:55
1 inch = 25.4 mm

Kyle M.
22-Mar-2016, 18:29
Metric size/25.4=inches.

Inch size X 25.4=mm.

David Lobato
22-Mar-2016, 20:39
There's an app for that.

Alan Gales
22-Mar-2016, 22:41
Just type in your inches and you get your millimeters. :)

http://www.metric-conversions.org/length/inches-to-millimeters.htm

Atracksler
23-Mar-2016, 03:28
Sorry, that was far more obvious than I had possibly imagined.

Doremus Scudder
23-Mar-2016, 07:04
Easiest, most precise and least technical: Inches x 25.4 = mm

It's easier for me to do this on a calculator than use a conversion app.

Also easy is memorizing a few approximate equivalents for common sizes: (2" = approx. 50mm so we count by twos) 4" = ~ 100mm, 6" = ~150mm, 8" = ~200mm, 10" = ~250mm, 12" = ~300mm, etc.

Doremus

DrTang
23-Mar-2016, 07:26
who knows - it's magic