alundeb wrote:
The measured T-stops are 1.4 and 1.6


But the f/1.4 has 2.1EV vignetting and the f/1.2 has 2.4EV, which is about 1/3 stop more. Wide open, the f/1.2 lens is not brighter than the f/1.4 lens in the corners.

Many would say this is more than they would try to fix in post for both lenses, so it doesn't matter. Others might want to correct the corners, and since this is about all the dynamic range headroom you might have on current Canon bodies, the f/1.2 is not practically shootable wide open for them.

(By f/2, vignetting on the f/1.4 lens has fallen to a usually correctable 1EV and on the f/1.2 lens to 0.75EV. Source:

http://slrgear.com/reviews/showproduct.php/product/140/cat/10
http://slrgear.com/reviews/showproduct.php/product/1000/cat/10

.)

I have the 50mm 1.4, and, as it turns out, I have a lot of other lenses. That said, there are other lenses that I would buy before upgrading my 1.4 to a 1.2. It is an upgrade, there is no doubt, but to me that money is better spent elsewhere given my perception of the relative performance of the 1.2 and 1.4 lenses (i.e. the 1.4 isn't really bad.) I would probably have a different priority if I shot much of my work at 50mm, but I tend to be wider or longer for the shooting that I do.

I am enjoying this thread. This reminds me of all the prior 50mm threads in the past.

FWIW I bought the 50L. It was worth it to me.... Had only a small part to do with the 1/2 stop

melcat wrote:
alundeb wrote:
The measured T-stops are 1.4 and 1.6


But the f/1.4 has 2.1EV vignetting and the f/1.2 has 2.4EV, which is about 1/3 stop more. Wide open, the f/1.2 lens is not brighter than the f/1.4 lens in the corners.

Many would say this is more than they would try to fix in post for both lenses, so it doesn't matter. Others might want to correct the corners, and since this is about all the dynamic range headroom you might have on current Canon bodies, the f/1.2 is not practically shootable wide open for them.

(By f/2, vignetting on the f/1.4 lens has fallen to a usually correctable 1EV and on the f/1.2 lens to 0.75EV. Source:

http://slrgear.com/reviews/showproduct.php/product/140/cat/10
http://slrgear.com/reviews/showproduct.php/product/1000/cat/10

.)


Neither one has even remotely enough vignette for my taste. In the old days I used a special filter for vignette but now I add it in PP.

Nobody compares 1.4 and 1.8 ?
Here we go:
http://photo.net/equipment/canon/ef50/

It's alot more on lenses other than the f-stops
I've used 1.4, 1.2 and not yet 1.0 or 1.8 and decided to keep my current stellar copy of the 50mm f1.2L.

hsk06 wrote:
It's alot more on lenses other than the f-stops


+10000

mttran wrote:
hsk06 wrote:
It's alot more on lenses other than the f-stops


+10000

+20000

I have both the 50/1.2 and the 50/1.4.

Stopped down, the difference in sharpness is very small. The 50/1.2 has usable sharpness wide open, the 50/1.4 not so.

The 50/1.2 has very good color and contrast, but the 50/1.4 is quite good in this regard too.

Build quality of th 50/1.2 is better.

The 50/1.2 is twice as heavy as the 50/1.4 (but that doesn't bother me)

The 50/1.2 has some CA when shooting wide open, the 50/1.4 has less CA. However, in the latest version of Lightroom this can be corrected very easy.

Everyone should dedice for theirselves if these differences are worth the (much) higher price of the 50/1.2. For me as I like shooting 50mm, this was a no-brainer

http://lex1963.home.xs4all.nl/foto/Lex/Canon_50_1.2.html

Hulot wrote:
so what reading do you get from your camera? what aperture can you dial in manually?

1.2 - 1.3 - 1.4 - 1.6 - 1.8 - 2
or
1.2 - 1.4 - 1.6 - 1.8 - 2

I am not owning a 50L so I cant tell

The 1DX + 50/1.2L shows 1.2, 1.4, 2 with full stop increments; 1.2, 1.4, 1.8 with half-stop increments; and 1.2, 1.4, 1.6, 1.8 with third-stop increments. Does this mean that f/1.2 is a magical f-stop that is all three; full-stop, half-stop, and third-stop? No. It's simply how Canon decided to implement its EV steps.

My discussion was about the definition and correct usage of f-stop. Nothing more. Saying that f/1.2 is a third stop different from f/1.4 is incorrect. It's based solely on geometry, and that's all. How it's implemented in a camera doesn't change the correct definition.

The t-stop discussion introduced by alundeb is based on how much light actually enters a lens,
http://www.fredmiranda.com/forum/topic/1146363/1#10943054

The discussion on how the 50/1.2L is different from the 50/1.4 includes f-stop, t-stop, and many other considerations. In this case, I'm talking about a well-defined, lens geometric property that is not based on how much light gets it, nor how a particular camera implements it. f-stop is f-stop, period.

jcolwell wrote:
gdanmitchell wrote:
You are absolutely correct that the difference between f/1.4 and f/1.2 is less than half a stop.

Nope. He's wrong. f/1.2 is a half stop larger than f/1.4. To be more precise, f/1.189 is a half stop larger than f/1.414. I think it's quite fair to round 1.189 to 1.2 and 1.414 to 1.4 - don't you?

The math is based on powers of sqrt(2). Here's lists of full stops, half stops and third stops from f/1 to f/4, rounded to one decimal place.

full stops
f/
1
1.4
2
2.8
4

half stops
f/
1
1.2
1.4
1.7
2
2.4
2.8
3.4
4

third stops
f/
1
1.1
1.3
1.4
1.6
1.8
2
2.2
2.5
2.8
3.2
3.6
4


P.S. there is no YMMV - it's all in the math.



Well your math is right, but the one thing we don't know is how Canon has rounded the numbers. The f/1.2 can come from rounding 1.189 up to 1.2 if indeed it is half stop, but it can also come from rounding down (√2)^(1/3) = 1.224, to 1.2 if we are talking 1/3 stops. So in fact f/1.2 could also be 2/3 stop faster than f/1.4.

I did not read the whole thread. But ever tried to focus manually with a Canon 1.4 or 1.8?
I like to have the possibility to change focus manually, when AF does not hit what I want it to. Ever tried this with a 1.8/1.4?

Ralph

Well with the 1.8 you need to push the AF switch to manual and the focusing ring is very thin. Not much fun to MF.
Additionally, I found that with the 50/1.8II I don't dare sell photo's that were taken below f/2.5. Between f/1.8~f/2.2 the image is too soft and it contains uneven soft spots across the frame. From f/3.2 it gets pretty good and by f/8 it is plenty sharp.
The 50/1.8II is good for street photography with apertures smaller than f/2.8. It is no good for weddings and the like.

Ralph Conway wrote:
I did not read the whole thread.Ralph
Too bad you missed the pizza part.......

Ralph Conway wrote:
I did not read the whole thread. But ever tried to focus manually with a Canon 1.4 or 1.8?
I like to have the possibility to change focus manually, when AF does not hit what I want it to. Ever tried this with a 1.8/1.4?

Ralph

The focus ring on the 50 f1/.8 is seriously a sick joke, it's about 3mm wide. The build of this lens is truly craptacular.

Pixel Perfect wrote:
Well your math is right, but the one thing we don't know is how Canon has rounded the numbers. The f/1.2 can come from rounding 1.189 up to 1.2 if indeed it is half stop, but it can also come from rounding down (��2)^(1/3) = 1.224, to 1.2 if we are talking 1/3 stops. So in fact f/1.2 could also be 2/3 stop faster than f/1.4.


Good points, Whayne.

I just measured the 50/1.2L apparent aperture as 42mm +/- 1mm (+/- 2.3%). That gives an f-stop of f/1.191 +/- 0.024, or from about f/1.17 to f/1.22. In any case, f/1.2 seems to be an appropriate value to use for the EF 50/1.2L.

Some lenses underexpose wide open. Some dont. If one underexposes half stop say 1.4 and 1.2 doesnt could be a stop. If 1.2 underexposes and 1.4 doesn't might be equal in speed. Be surprised if a big difference at f/8.

Moved the AF/MF 5Dc+50L samples to a separate topic:

http://www.fredmiranda.com/forum/topic/1147523

With all of the discussion on light difference and transmission loss I went on over to DXO to see if they had T Stop ratings in their lens reviews. Not only do they have them I was rather surprised when I discovered that they seem to vary from body to body... for example, according to DXO's tests, the 50 f/1.2L has a T Stop rating of:

1.4 on the 1DsIII,
1.5 on the 5DII,
1.6 on the 7D, and
1.7 on the 450D

If that is true then you could be looking at a transmission loss of anywhere from a half stop to one full stop depending on what body you have. I went ahead and sent this over to Roger at LensRentals as a topic/test suggestion for their blog as I'd be interested to see this is in fact true.

@dshipley

snapsy already mentioned that in this very thread :
http://www.fredmiranda.com/forum/topic/1146363/0#10942644

To answer your question, technically: by moving from 1.4 to 1.2, you get approximately 25.99% more light.