Graflex.org

[RichS]

I thought I'd post this here in case anyone was interested.

Seems everyone asks the same question at least once. "What 4x5 lens is equal to my 28mm on my 35mm camera" or some variation. Or what angle of view will a 90mm lens have on a 4x5...
Most all answer I see equate lenses on the film diagonal. I didn't mind that for quite a while until I wanted a specific coverage. But who shoots film on a diagonal? I am concerned with the coverage on the long side of the film for a particular lens, especially wide angles. So I did some searching and found a formula that calculates a lens angle of view for a particular format. It's not exact, but close enough for comparisons. I then created a spreadsheet that allows entering in a lens focal length which gives th angle of view for the 4 formats I use. You can also enter a desired AOV and get back the lens focal length that gives that angle for the formats. I also created a chart starting from 1/8 inch and up to 60 inches and shows the AOV for each in the 4 formats. This all prints out to a 10 page chart and is very handy( for me anyway). So if anyoen has any interest in the spreadsheet, it's avalable in both excel and Lotus 123 formats at:
http://www.southbristolviews.com
at the bottom of the left menu.
Any suggestions are always welcomed, except adding the diagonal!


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"Ya just can't have too many GVIIs"
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[Tiltall ED]

I'm confused by your concept of diagonal!

I do not think it means using your camera, or taking a picture on a diagonal plane.

But when given for any lens, set at infinity, and focused on the camera's film plane, and viewing glass size. Or whatever film size you are using. A lens projects a circular image at the film plane, the film used is a square or rectangular masked area within this image circle, or the covering power of a lens, focused apon the film, or expressed as the maximum film size that can be used with the lens, the diameter of the circle of good definition, or angle of coverage. With the film size area, inscribed within this area, the diagonal being the diameter of good definition, and should be larger than the diagonal of the film mask size, allowing for more movement, or croping with the view camera.
So the width times height squared, where width=5, squared is 25, and height=4, squared is 16.
Added , 25+16= 41 which is the diagonal squared (or hypotenuse) and by finding the sq. root of 41= the length of the diagonal, being, 6.4031242 ( in this case inches)

Oh! Yeah, I almost forgot! Could you give a link for your spreadsheet, saved as a PDF files for us Macintosh users, either posted here or on your web page.

Thanks!



_________________
Only you and a camera, can capture an image, a moment of time, in a fraction of time! Why wait?

"Oh babe!, you're a hefty one!, spread your legs, raise up a little, turn to the left, and now right! You're the most beautiful................. tr

[ This Message was edited by: Tiltall ED on 2005-02-26 17:57 ]

[RichS]

You miss the concept of 'diagonal'. It has nothing to do with the camera and I stated "film diagonal". Again, it is the most 'standard' way people equate one format film to another when talking lens equivilents. And it is this I didn't agree with. It also has nothing to do with lens coverage. That's a whole different subject. The spreadsheet is strictly about equating a lens _viewing_ angle or coverage from one format to another format. Say a 21mm from a 35mm camera to a 75mm for a 4x5 camera.

Maybe you should just read my post again because every time I think of how to explain it again, it comes out the same way...

And what sense would it make to have an interactive spreadsheet converted into a static PDF image file? Sorry, it would lose it's function... There must be some spreadsheet program for the Mac that can translate a Lotus 123 or MS Excel file into it's native format. Sorry I can't help, but I don't use a Mac...

[Tiltall ED]

Well ! You sure haven't seen my lady friend use a camera ! She twists and turns that darn thing all sorts of diagonal ways !

Yah know what pard'nar, some of her photo's look pretty good !!

And she's pretty handy with spreadsheets too !, in fact when she saves them, she can save them as Excel or any other Windows format, and she uses a Mac, duel 2.0 GHz, G-5, to do it so that any computer user can read them!!

As for your spreadsheet, I did not try to download it, even if my G-5 can open it. I must of been off on a diagonal while reading the posts here!
Something I could really learn and interact with!





_________________
Only you and a camera, can capture an image, a moment of time, in a fraction of time! Why wait?
"Oh babe!, you're a hefty one!, spread your legs, raise up a little, turn to the left, and now right! You're the most beautiful.... tripod I use!

[ This Message was edited by: Tiltall ED on 2005-03-02 02:41 ]

[ This Message was edited by: Tiltall ED on 2005-03-02 02:43 ]