100 f/2 or 85 f/1.8 - CA / Sharpness diff?

My 85 f/1.8 is a great focusing lens and in poor lighting conditions works well, but in strong lighting and wide open, there is a lot of CA.

Is the 100 f/2 any better? I know they're cousins but are they twins?

The 100 f2 isn't any better in the CA/fringing department so in that regard, yes they are like "twins".

n1as wrote in post #7969540
My 85 f/1.8 is a great focusing lens and in poor lighting conditions works well, but in strong lighting and wide open, there is a lot of CA.

Is the 100 f/2 any better? I know they're cousins but are they twins?

nicksan wrote in post #7969573
The 100 f2 isn't any better in the CA/fringing department so in that regard, yes they are like "twins".

I've always thought the 100 is slightly better when it comes to PF and CA, but that's from hearsay. I've never yet shot with one.

Kind regards, Wim

Yeah, they are like twin brothers that are identical except one at his veggies and grew a tad taller.

Every test I have ever seen has them with identical optics (including CA) and AF. You just have to pick between an extra 1/3 a stop of light, or an extra 15mm of reach.

I was just thinking, an 85/1.75 and a 100/f2.05 would have the same physical aperture sizes. Maybe the lenses even have identical aperture mechanisms, too and that is why the 100 is a tad slower. The numbers could just be rounded to the clean 1/3 stops while not being exactly 1.8 and f2. Elements, AF motors and aperture elements could all be shared, with only the physical barrel being a couple mm longer on the 100. Sounds like a good plan for Canon and cheap to make 2 lenses that way.

tkbslc wrote in post #7969799
Yeah, they are like twin brothers that are identical except one at his veggies and grew a tad taller.

Every test I have ever seen has them with identical optics (including CA) and AF. You just have to pick between an extra 1/3 a stop of light, or an extra 15mm of reach.

I was just thinking, an 85/1.75 and a 100/f2.05 would have the same physical aperture sizes. Maybe the lenses even have identical aperture mechanisms, too and that is why the 100 is a tad slower. The numbers could just be rounded to the clean 1/3 stops while not being exactly 1.8 and f2. Elements, AF motors and aperture elements could all be shared, with only the physical barrel being a couple mm longer on the 100. Sounds like a good plan for Canon and cheap to make 2 lenses that way.

They're very similar, but not the same. The 85 F/1.8 has a lens element (and a lens group) extra.

Looking at the block diagram, they are really only similar for the first 4 elements, and even those first four are different.

Kind regards, Wim

well there goes that theory!

Sounded good in my mind.

tkbslc wrote in post #7969870
well there goes that theory!

Sounded good in my mind.

Well, they are related to each other. They certainly look like they were designed in tandem , and they might share the diaphragm mechanism, who knows .

Kind regards, Wim

The photozone.de tests would seem to confirm the general similarity of the two lenses, but the better CA/fringing behavior of the 100mm. From the 100mm f/2 review: "It's interesting that the figures are marginally better compared to its more popular sister lens (EF 85mm f/1.8 USM)."

8 Mp APS-C Reviews:
85mm: http://www.photozone.d​e …8-usm-test-report--review
200mm: http://www.photozone.d​e …m-lab-test-report--review

15 Mp APS-C Review:
85mm: http://www.photozone.d​e/canon-eos/421-canon_85_18_50d

FF Review:
85mm: http://www.photozone.d​e …eos_ff/419-canon_85_18_5d

It's been a while since I've owned the 85 1.8 so...

But CA/PF is clearly evident even on scenes with modest contrast but that's really no surprise.

I am trying to recall how the 135L performed in this regard.

The 100 f2 is great for street shooting and that's what I have been using it for. A nice and cheaper alternative...but the 135L is definitely calling me...again...for the third time. But I think I have now "discovered" the ~100mm focal length, so much so that I can definitely imagine myself hanging on to the 135L now!

wimg wrote in post #7969795
I've always thought the 100 is slightly better when it comes to PF and CA, but that's from hearsay. I've never yet shot with one.

Kind regards, Wim

"Better" relative to the 85 1.8...sure...but it still easily CA's/Fringes.
Yuk...but then again, I am probably spoiled by my 200L, which never seems to exhibit CA/fringing!

How is the 135L in that regard? Better? Worse? About the same as the 85 1.8/100 f2?

GeoffSobering wrote in post #7969923
The photozone.de tests would seem to confirm the general similarity of the two lenses, but the better CA/fringing behavior of the 100mm. From the 100mm f/2 review: "It's interesting that the figures are marginally better compared to its more popular sister lens (EF 85mm f/1.8 USM)."

8 Mp APS-C Reviews:
85mm: http://www.photozone.d​e …8-usm-test-report--review
200mm: http://www.photozone.d​e …m-lab-test-report--review

15 Mp APS-C Review:
85mm: http://www.photozone.d​e/canon-eos/421-canon_85_18_50d

FF Review:
85mm: http://www.photozone.d​e …eos_ff/419-canon_85_18_5d

From lightrules' comparison. View "original" size and look at the wheel shot for CA. Looks about just as bad on the 100 (or maybe worse in this shot).

http://www.pbase.com/l​ightrules/image/808816​68

nicksan wrote in post #7969939
"Better" relative to the 85 1.8...sure...but it still easily CA's/Fringes.
Yuk...but then again, I am probably spoiled by my 200L, which never seems to exhibit CA/fringing!

How is the 135L in that regard? Better? Worse? About the same as the 85 1.8/100 f2?

Well, IME, the 85 F/1.8 is really bad in this regard (worst lens I have experienced when it comes to PF), and I haven't noticed any yet with the 135L, while it only took two shots to notice this with the 85 ... .

Kind regards, Wim

Wimg.

Not good for Mr. Wallet. Not good at all!
It figures...I went through 2 135L's already. Each time it got lost in the mix. But I've discovered the FL...and want one badly. And when I do, the prices go up. (Got my first one for something like $700 IIRC!) That's life I suppose.

The 100 f2 is really a nice lens. But you know how superficial I am with the "L" lenses right?

wimg wrote in post #7970064
Well, IME, the 85 F/1.8 is really bad in this regard (worst lens I have experienced when it comes to PF), and I haven't noticed any yet with the 135L, while it only took two shots to notice this with the 85 ... .

Kind regards, Wim

nicksan wrote in post #7969931
It's been a while since I've owned the 85 1.8 so...

But CA/PF is clearly evident even on scenes with modest contrast but that's really no surprise.

I am trying to recall how the 135L performed in this regard.

The 100 f2 is great for street shooting and that's what I have been using it for. A nice and cheaper alternative...but the 135L is definitely calling me...again...for the third time. But I think I have now "discovered" the ~100mm focal length, so much so that I can definitely imagine myself hanging on to the 135L now!

From my experience so far, no comparison. The 135L is way better in this regard, without a doubt .

Kind regards, Wim

Wim...you are pure evil. EVIL!

wimg wrote in post #7970090
From my experience so far, no comparison. The 135L is way better in this regard, without a doubt .

Kind regards, Wim