How to Figure Friggin Focal length and f Stop Thingies.

[Ole]

Instead of measuring the distance from the wall to the node (wherever that may be), I measure the size of the projected image of the window. You will need a few more calibration points for this, but it has the great advantage that it works equally well for telephoto lenses and others where you don't know where the node is.

My "calibration set" is a casket set with 7 cells from 150mm to 750mm focal lengths. That gives me a sheet of cardboard with eight lines - left edge of the window, and one line for each 100mm step. Projecting the image of the window with the left edge lined up with the base line, it's easy to read off the focal length directly to within a +/- 10mm tolerance.

Without a casket set some calculation may be needed to make FL lines on the cardboard, but three or four known lenses should be enough.

Tortellini are too large for this, but spagetti-widths should be a useable unit of measure.

 

[Uhner]

Cool. I will try this on the lens on my Bilora Bonita.

Cheers

Claes

 

[richard ide]

Mention of "Marco Polo" brings to mind the little known fact that he was probably the first venetian blind.

 

[removed account4]

jason

you git another film award for this one

good stuff you make, but...
you didn't eat your props this time around ?
guess you are on a low carb, low-cheese diet

john

 

[matti]

But how much tortellini do you need for ten feet?

/matti

 

[JBrunner]

But how much tortellini do you need for ten feet?

/matti

Larger measurements can be made in other units, like bread loaves, or women.

 

[Ian Grant]

Larger measurements can be made in other units, like bread loaves, or women.

We worry about you Brunner, but I suppose we have to allow for it after all you are in SLC.

But are those American women units, or the very much slimmer EU women units

Ian

 

[matti]

Larger measurements can be made in other units, like bread loaves, or women.

I see, five women = ten feet, right. Thanks for the tip!

/matti

 

[JBrunner]

We worry about you Brunner, but I suppose we have to allow for it after all you are in SLC.

But are those American women units, or the very much slimmer EU women units

Ian

uh... one woman= two hand widths ...

(God... I'll likely get flamed, by a righteous babe, and rightly so)

 

[wheelygirl]

Hello, to one and all!
If you guys haven't noticed you are all a bunch of delightful loons as in loony! Thanks JB, for the good-quality giggles!!

 

[DarkroomExperimente]

Hello, to one and all!
If you guys haven't noticed you are all a bunch of delightful loons as in loony! Thanks JB, for the good-quality giggles!!

I'm confused about the loon linear measurement method

do you stretch out the loon's neck all the way?

 

[wheelygirl]

Dear DE
Yes, but oh so gently, so as not to harm the poor critter!