85mm dilemma L vs. 1.8

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Archive 2011 · 85mm dilemma L vs. 1.8

Grantland
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p.5 #1 · 85mm dilemma L vs. 1.8

i like these shot at f/1.2

i also have the f/1.8 and use it primarily for indoor sports.

grant

Dec 31, 2011 at 03:58 PM

RobertLynn
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p.5 #2 · 85mm dilemma L vs. 1.8

D. Diggler wrote:
RobertLynn wrote:

Just a small point, there is not a full f stop between f/1.2 and f/1.8.

I think the more important question than just looking at the f-stop scales is actual light transmission difference between the two lenses. When I was considering buying the L I actually did that comparison test when I had both lenses. Put both on a tripod aimed at the same subject and measured the light transmission at various wide f-stops. Don't have the results right at hand but I could look back at the image files again if anyone's interested in having the definitive answer.

I think you have quoted the wrong person. I did not say there was "not a full f stop between f/1.2 and 1.8". That was someone else. I quoted them, and said that I feel that they are incorrect, that there's actually MORE than 1 f/stop.

I don't mind being quoted, but please make the whole comment available.

stanj wrote:
RobertLynn wrote:

Just a small point, there is not a full f stop between f/1.2 and f/1.8.

That's correct. It's actually more than one stop. (1.8/1.2)^2 = 2.25, i.e. more than one stop, by more than just a rounding error.

Stan, not sure if you saw the "full" quote of what I said, because the above isn't the full statement, and the "just a small point...f/1.8" was me quoting someone else. I was using their scale, and I said that there's more than 1 f/stop.

Marko wrote this,
marko1953 wrote:

"Since there is a stop between 1.8 and 1.2, ".

Just a small point, there is not a full f stop between f/1.2 and f/1.8.
Typical one-quarter-stop f-number scale
f/# 1.0/ 1.1/ 1.2 /1.3 /1.4/ 1.5/ 1.7/ 1.8/ 2/ 2.2 /2.4/ 2.6/ 2.8

<~~~~~~~~~~~~~~~Marko

And I responded to it with, the below post. For whatever reason it has the "whole post" in white, like I wrote it, but I only wrote from, "Perhaps I'm confused....seeing photos you post".

I am sorry for the confusing. I was just questioning the guy *(marko) who said that there's not a full f/stop, but pointing out in 1/4 increments, that it's MORE than one f/stop.

marko1953 wrote:

"Since there is a stop between 1.8 and 1.2, ".

Just a small point, there is not a full f stop between f/1.2 and f/1.8.
Typical one-quarter-stop f-number scale
f/# 1.0/ 1.1/ 1.2 /1.3 /1.4/ 1.5/ 1.7/ 1.8/ 2/ 2.2 /2.4/ 2.6/ 2.8

1.21.8 <~~~~~~~~~~Marko

Perhaps I'm confused. A quarter of something is 1/4. Meaning 4/4 is 1, and 5/4 is 1 and 1/4.

Start at 1.2
Move up 1/4 to 1.3 (1/4)
Move up 1/4 to 1.4 (2/4)
Move up 1/4 to 1.5 (3/4)
Move up 1/4 to 1.7 (4/4)
Move up 1/4 to 1.8 (5/4).

Isn't that more than one f/stop? Maybe it's the metric system and I'm confused.

@daweiye. Dude, don't you ever talk down your stuff again. You're an excellent photographer. It's not as often as I would like, but I enjoy seeing the photos you post.

Dec 31, 2011 at 04:46 PM

RobertLynn
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p.5 #3 · 85mm dilemma L vs. 1.8

marko1953 wrote:
stanj wrote:
RobertLynn wrote:

Just a small point, there is not a full f stop between f/1.2 and f/1.8.

That's correct. It's actually more than one stop. (1.8/1.2)^2 = 2.25, i.e. more than one stop, by more than just a rounding error.

I think you are right!!!
If we multiply the diameter of any circle by the square root of 2 we have calculated a revised diameter that is twice as big. Stated another way, to double the light gathering power of a lens we multiply the current diameter by 1.414. We don’t need to be so exact so we can use a shortened value of 1.4.

Conversely to reduce the light entering the camera by half, we multiply the current diameter by 0.707. This is the inverse of 1.4. We can also divide by 1.4 to get the same answer but the preferred way is multiplication by 0.707.

With the initiation of electronic light metering and precision lens making, it became possible to fine-tune the diaphragm using 1/2 f/stop adjustments. The multiplier is the fourth root of 2 which is 1.189. For finer adjusts, (mostly never needed) 1/3 f/stop which uses the sixth root of 2 which is 1.122

Full f/stop number set using 1.4

1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 – 32 – 45 – 64

Note each value going right is its neighbor on the left times 1.4.

Each number going left is its neighbor on the right times 0.707.

½ f/stop number set using 1.189
1 – 1.2 – 1.4 – 1.7 – 2 – 2.4 – 2.8 – 3.4 – 4 – 4.8 – 5.7 – 6.7 – 8

1/3 f/stop number set using 1.122
1 – 1.1 – 1.3 – 1.4 – 1.6 – 1.8 – 2 – 2.2 – 2.5 – 2.8 – 3.2 – 3.5 – 4 – 4.5 – 5 – 5.6

So going up from f/1.2 , (x 1.4) you get f/1.7 (rounded up slightly)
So you are correct......
the difference between f/1.2 and f/1.8 is actually slightly more than a full f stop

Thank you. I believe that Stan, and the other gentleman thought that I was stating it differently, because only part of the quote was used, and also that for whatever reason, when I quoted you, the text appeared as white, as if I wrote it.

Dec 31, 2011 at 04:50 PM

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