How to determine max enlarging size for my setup?

Ian C · Feb 23, 2014

Eliminate the outer pair of parentheses to the right of the division slash.

We want to divide the quantity to the left of the slash by 2f, and then subtract 1.

I think that Excel follows the standard order of operations for algebraic expressions so that we can eliminate extraneous parentheses (which makes the expression easier to read as well).

It should look like the original formula.

= (d + sqrt(d^2 – 4*d*f) ) / 2*f - 1

gleaf · Feb 23, 2014

Used to do 35mm KB14 (asa 25) to 20x24 in the late '60's and early '70's when I had a lab available with a Navy grade Omega D series. If you want really big with limited grain the film and ASA options become seriously reduced. I believe some Dursts will roll over to Horizontal for long throws and really big images.

Doremus Scudder · Feb 23, 2014

Ian C said:
Eliminate the outer pair of parentheses to the right of the division slash.

We want to divide the quantity to the left of the slash by 2f, and then subtract 1.

I think that Excel follows the standard order of operations for algebraic expressions so that we can eliminate extraneous parentheses (which makes the expression easier to read as well).

It should look like the original formula.

= (d + sqrt(d^2 4*d*f) ) / 2*f - 1

Aahh... The problem is not my Excel formula, but rather my misunderstanding of the original!

Got it now! Thanks a million Ian.

...and, for those who want the right Excel string:

=(((SQRT((d^2)-(4*d*f)))+d)/(2*f))-1

Just replace "d" with the cell you want to enter the distance in and "f" with the cell you want to enter the focal length in.

Best,

Doremus

ROL · Feb 23, 2014

I imagine the OP to be happily enlarging away after some 2½ years. Don't forget when calculating maximum enlargement for the purposes of designing a table capable of handling said enlargements, to account for room to crop unless you're one of those inflexible, full frame, crop Nazis.

PKM-25 · Feb 23, 2014

MattKing said:
Dan:

While you are at it, see if you can convince the light source manufacturer to:

1) provide an Android App for it; and
2) develop an f-stop timer App as well .

If I am not mistaken, the B version should allow for the use of a separate timer.

How to determine max enlarging size for my setup?

Ian C

gleaf

Doremus Scudder

ROL

PKM-25

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