85 f/1.2 L II vs. 85 f/1.8 : How Much Brighter?

[Fleetie]

I currently have the 85mm f/1.8 , and I'm thinking about getting the 85mm f/1.2 L II version.

I think:

Stops_Difference = 2 * log_2 ( f_no_1 / f_no_2 )

So in this case:

Stops_Difference = 2 * log_2 ( 1.8 / 1.2 ) = 2log_2(1.5) ~= 1.17 stops.

So, superficially, one might expect to gain just over 1 stop of extra brightness by using the L lens.

But that assumes that the optical transmittance of the lens as a whole remains the same.
Given all the extra glass thickness (I am guessing) in the f/1.2 model, do we really get that much extra
light?

How much brightness gain do we *really* get?

 

[akiskev]

In this case you get what you expect. 1 full stop of extra brightness!
Apart from that, you get more creamy out of focus parts too! Compared to the 85mm 1.8, the 1.2L does not suffer from bokeh fringing and octagonal highlights at medium diaphragms.
The drawback? Slower autofocus speed due to the massive optic elements!
Hope I helped.

85 1.2L

85 1.8

 

[Loswr]

According to the DxOMark measurements, the 85L has a full stop greater transmission (1.4 vs. 2.0 T-Stops). So, the 85L loses a little bit more light (relatively) with the greater amount of glass.

In practice, on my 7D (which is the only body on which I've shot both lenses), the 85L appeared to meter a little brighter than the 85/1.8. Not sure if that's a firmware characteristic specific to the 7D, or more general.

By way of general comparison between the two lenses (I currently have the 85L, had the 85/1.8 before that), the 85L is slightly sharper, has a bit less longitudinal CA (bokeh fringing), and IMO delivers better color and contrast. The 85L also focuses much slower.

Overall, I'm very pleased with the 85L and glad I upgraded from the 85mm f/1.8 (although I wouldn't want to shoot sports with the 85L).

 

[Fleetie]

Thanks, guys.

I was worried that all that extra glass thickness might significantly negate the extra light grasp.

As my camera is a 7D, I need all the light I can get.

I won't have the money for a few months yet, and when that time comes, if a 5D3 is looking imminently available (i.e. has been announced and looks to be in the shops soon) I'll probably get that first. If the 5D3 is still looking ages away, I'll get the 85L.


Martin

 

[Axilrod]

Thanks, guys.

I was worried that all that extra glass thickness might significantly negate the extra light grasp.

As my camera is a 7D, I need all the light I can get.

I won't have the money for a few months yet, and when that time comes, if a 5D3 is looking imminently available (i.e. has been announced and looks to be in the shops soon) I'll probably get that first. If the 5D3 is still looking ages away, I'll get the 85L.


Martin

Dude with all the lenses you have youd be crazy to buy an 85L, get a damn 5D2! Especially now that the 5d is 2000. You'll effectively have more lenses with the diff sensor sizes. I love my 85L but much more on a full frame.

 

[Orion]

I currently have the 85mm f/1.8 , and I'm thinking about getting the 85mm f/1.2 L II version.

I think:

Stops_Difference = 2 * log_2 ( f_no_1 / f_no_2 )

So in this case:

Stops_Difference = 2 * log_2 ( 1.8 / 1.2 ) = 2log_2(1.5) ~= 1.17 stops.

So, superficially, one might expect to gain just over 1 stop of extra brightness by using the L lens.

But that assumes that the optical transmittance of the lens as a whole remains the same.
Given all the extra glass thickness (I am guessing) in the f/1.2 model, do we really get that much extra
light?

How much brightness gain do we *really* get?

visit this page if you want another opinion that compares all versions:

http://www.the-digital-picture.com/Reviews/Canon-EF-85mm-f-1.2-L-II-USM-Lens-Review.aspx

 

[Edwin Herdman]

How much brightness gain do we *really* get?

Well, that's an answer you'll only get if you measure both lenses in T-stops. In terms of the difference in brightness, though, I think it's got to be very close to the number you came up with - just over 1 stop extra aperture should equate to the same amount of extra brightness.

 

[Forceflow]

Have you considered the Sigma 85 1.4? I find this one a very nice compromise between the 1.2 and 1.8 that Canon offers. It's not cheap, but only costs about half of the Canon 1.2. The copy I have is perfect and what I found on the internet in terms of quality was all really good.
I know a lot of people shun Sigma, but I find that they have some very interesting high quality in-between lenses. And as long as you buy it in a brick and mortar store that let's you test the lens on your body the QA problems Sigma might have isn't really an issue.

 

[Loswr]

As my camera is a 7D, I need all the light I can get.

Dude with all the lenses you have youd be crazy to buy an 85L, get a damn 5D2! Especially now that the 5d is 2000. You'll effectively have more lenses with the diff sensor sizes. I love my 85L but much more on a full frame.
[/quote]

I've got to agree with Axilrod on this one. I, too, had a 7D and wanted more light. As you are considering, I did change out my 85/1.8 for an 85/1.2L II. Yes, it's great on a 7D. But then I got a 5DII. Since then, the only lenses that have been mounted on my 7D are the 100-400mm for shooting birds, and the 17-55mm a few times (because when hiking to shoot birds, I'd rather carry just another lens instead of a second camera and lens). For everything else, I use the 5DII.

In fact, I had a similar discussion to this one on TDP at the time, and one of the responses was, literally, "Dude, just get a 5DII!" (sounds eerily familiar!).

One good point from that discussion - since the crop factor affects effective focal length, but also effective aperture in terms of depth of field, the 7D + 85mm f/1.2L yields almost exactly the same framing and DoF as the 5DII + 135/2L. Using a lens that costs half what the 85L does, on a FF body, yields IQ that's substantially better than the 85L on the 7D. Eventually, I actually tested them head-to-head.

 

[Fleetie]

Neuro, that was an very interesting, well-executed and thorough comparison you did between the 2 options.

I cannot dispute your conclusion about IQ either. It speaks for itself.

But in my particular case, I absolutely refuse to buy a 5D2 at its current point near the end of its life-cycle. I am not desperate for a FF camera. I love my 7D, and I can, and will, hold onto it until the 5D3 comes out. Actually, I do most of my shooting in the spring/summer anyway, so winter is a quiet time for me, photographically, so I currently have no problem sitting on my 7D and waiting.

Basically, I like what my 85/1.8 gives me on my 7D, but I'd like a stop more of light. This thread tells me that the 85/1.2 will give me just that, plus better bokeh.


If I do decide to buy the 85 f/1.2 L II, I can gain light now, on my 7D, and still enjoy its awesome IQ and bokeh when I get the 5D3. albeit with different framing. If at some point, I want the 135 L, then I can still go ahead and buy that.

If I buy the 5D2 now, I'll simply have to sell it when the 5D3 comes out. (Well, not HAVE TO, but I would do so. I'll definitely KEEP the 7D.)

Nevertheless, I am grateful for the opinions put forth by the contributors to this thread.

 

[Edwin Herdman]

Somehow I'm not surprised Neuro would have a couch like that.



(There's a couch with the same pattern here but in green instead...whether that signifies something I can't say.)

Great comparison anyhow - the 5D does much better in that scene, especially on the solid back wall and metallic highlights (the text on the actual SpyderCube didn't really convince me for the 5D at f/2 but it is better in all other apertures and all other parts of that image crop).

I've been seriously considering the FF camera (or at least 1.3X if one is made available, against all expectations, at a 7D- or 5D-like price) and this doesn't hurt that notion. I do like having a longer lens but the myriad IQ problems are somewhat aggravating.

 

[Loswr]

Somehow I'm not surprised Neuro would have a couch like that.



(There's a couch with the same pattern here but in green instead...whether that signifies something I can't say.)

LOL. Actually, that's just a couch cover - something that comes in handy with two toddlers in the house! ;D

 

[epsiloneri]

Eventually, I actually tested them head-to-head.

Very nice test. The reason the FF wins out is probably that it is much more difficult to manufacture a lens that produces the same IQ on APS-C as on the FF, even with (almost) identically (for the scale) spec:ed lenses. The 85/1.2L lens would also have to be 1.6x sharper than the 135/2.0L in order to be fully equivalent, which it clearly isn't. This is also the reason why one shouldn't expect L-glass to always outperform EF-S lenses on APS-C sensors, even if they are legendary on FF. Same thing applies to MF lenses on FF - not necessarily a good idea!

 

[Loswr]

This is also the reason why one shouldn't expect L-glass to always outperform EF-S lenses on APS-C sensors, even if they are legendary on FF.

I certainly don't - there's plenty of evidence that the 17-55mm beats out both the 24-70mm and 24-105mm when all are compared on the same APS-C body. Even the lowly 18-55mm kit lens, stopped down a bit, beats out many L lenses at similar apertures.