


As I understand it, among nonphotographic chemists, there is a difference, but in photographic chemistry, the + and : are used interchangeably. I've taken to using the + symbol to avoid the ambiguity.

Originally Posted by lee
I agree with Dan (dancqu) 1:2:100 = 1+2+100
lee\c
The plus, "+", is what I used now and then. Using it is a step
towards spelling it out.
Now I don't think the + should be used. Using it is a step away
from the universally used : for denoteing ratios. Dan

Originally Posted by Bruce (Camclicker)
Then, if you are saying "to", you
mean 2 parts diluted "to" five parts ...
thanks to all
I nor yourself in your OP did mention "diluted". Ratios, one : one,
1:1, one to one, 1 to 1. The convention is the colon, : . Dan

Oh come on guys, must you make photography this complicated???

Originally Posted by Bruce (Camclicker)
Is a ratio of 1:2, 1 part X plus 1 part Y to make 2 parts or is it 1 part X plus 2 parts Y to make a combined 3 parts?
Would a PMK developer that calls for combing parts of 1:2:100 yield 100 ml or 103?
Bruce;
When you are working with photographic chemistry, make it easy on yourself and change all the colons ":" to plus signs "+". This is the way it should be expressed anyway.
True ratios will just mix you up, and in reality can't normally be expressed in an easy way when using more than two like quantities (like mls). In other words, the PMK "ratio" is expressed incorrectly simply because it has more than two quantities. It should be 1+2+100, and that's really the only way it makes sense here.
Just in case you want to know, to express a developer dilution of (one part Dektol plus two parts water) in a ratio, it would be written 1:3. The second numeral of a ratio (the three in the Dektol example) is the total of parts needed for the solution. The first numeral (the 1) indicates one of the parts that make up the total, in this case the Dektol. Mechanical ratios work the same way, (think of two pulleys, one three times the size of the other). The larger pulley is three feet in diameter, the smaller one foot. One rotation of the larger rotates the smaller three times. A ratio of 1:3.
If this is all mush to you, just go back to my first sentence and mix with confidence.
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Originally Posted by Dean Williams
...to express a developer dilution of (one part Dektol plus two parts water) in a ratio, it would be written 1:3. The second numeral of a ratio (the three in the Dektol example) is the total of parts needed for the solution. The first numeral (the 1) indicates one of the parts that make up the total...
So then a dilution of 1:1 would be a solution with one part of the
first numeral and zero parts of what ever else; the second numeral
minus the first equalling zero. "The second numeral of a ratio...is
the total of parts... .
Any wonder I'm not convinced?

Originally Posted by dancqu
So then a dilution of 1:1 would be a solution with one part of the
first numeral and zero parts of what ever else; the second numeral
minus the first equalling zero. "The second numeral of a ratio...is
the total of parts... .
Any wonder I'm not convinced?
Thank you! I was wondering if I was the only one who saw the problem.

Talk about a tempest in a teapot. Get back to work fellas
Mark Layne
Nova Scotia
and Barbados

I used to know how to mix photographic chemicals. Now I have no idea what I'm doing. Send help. My head is about to explode!

Originally Posted by dancqu
So then a dilution of 1:1 would be a solution with one part of the
first numeral and zero parts of what ever else; the second numeral
minus the first equalling zero. "The second numeral of a ratio...is
the total of parts... .
Any wonder I'm not convinced?
Look, I just put that last part in there in case Bruce wanted to know how a TRUE ratio was figured.
If we all just replace the colon in a dilution with a plus it will save a lot of head scratching. Remember that first of all.
When Kodak says "D76 1:1" they mean one part D76 and one part water. I don't know why they use the ratio thing here (the colon) instead of a plus sign. It's been used for a long time though, and they probably won't change it. I'm sure the chemists who work for Kodak know the difference between a ratio (expressed with a colon) and additive notation (expressed with a plus sign). We want additive notation to make things easier, and, so things like a ratio of 1:1 don't cause so much misunderstanding.
The definition of a ratio is: "The relation of two quantities of the same kind." So, the ratio of:
1:0 is a misnomer. You can't have a ratio with only one quantity
1:1 is what we call stock solution. One part developer in a total of one part. That's a 100% solution.
1:2 is half stock and half water.... and so on.
There are three ways to express a ratio, and maybe this will help clear things up: 1:1 or 1/1 (like a fraction) or 1 divided by 1. If you use the fraction method you will see that a 1:1 ratio is 1 or for our purposes, stock solution.
Again, Kodak uses the colon to denote an additive notation, while Ilford and Agfa (and others) use the more conventional plus sign.
Just remember to replace the colon with a plus sign and all this ratio stuff won't matter.
[COLOR=Sienna][FONT=Arial]Some days are diamonds. Some days a tree crashes through your roof.[/FONT][/COLOR]

