Quote:Polarisers at such wide angles? Even at 24mm there is usually a very obvious sky gradient effect when used outdoors, unless there are other applications where this isn't a problem?
Not sure why you say this. The sky is only a problem if you over rotate the CPL. In any case polarizers are needed if you want to redue reflections. But more importantly, without a filter thread it would make working with high ND filters a pain.
Having said this, I want to use this lens for night photography, so filters are not such an issue. For me, the lens needs to be good to great at f1.4.
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Quote:Polarisers at such wide angles? Even at 24mm there is usually a very obvious sky gradient effect when used outdoors, unless there are other applications where this isn't a problem?
24mm with polarizer:
http://dave9t5.zenfolio.com/p869197257/e3bb6a67d
24mm with polarizer:
http://dave9t5.zenfolio.com/p869197257/h...#h266d9934
In the former, the vertical format has the same width as roughly a 50mm lens.
In the latter, the clouds partially obscure the lateral gradient, but the polarizer also cut a lot of glare off the asphalt and foliage.
That said, with 24mm you do have to be careful with composition and angle to the sun. Polarizer with 20mm is probably too limiting for me, but obviously rules are meant to be broken.
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35mm is the same vertical as 50mm hoizontal 
So, 24mm vertical is similar to ~35mm horizontal.
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Quote:The MTF is at f1.4. So, pretty good, considering. It will no doubt perform pretty well closed down a bit. Heavy beast, though.
I can't imagine having a bag full of top primes, nowadays... Sigma 20mm f1.4, Zeiss Otus 28mm f1,4, Canon 35mm f1,4 II, Zeiss 50mm f1.4 Milvus, Canon 85mm f1.2, what a heavy bag that is going to be!
BC, I agree with you, every producer is after F1.4 or 1.8 and extra weight, and extra $. IMO f2.0 will do the trick for most of us (non pro users) and will save on weight and money.
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I think I wait until they bring the first 20-500/2 on wheels. Can't be much heavier than all of the latest glass.
I sold my wheelbarrow to pay for my AF20mm F2.8, I no longer need it!;... 
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Quote:35mm is the same vertical as 50mm hoizontal
So, 24mm vertical is similar to ~35mm horizontal.
Ah, thanks. Couldn't figure it out exactly off the top of my head. Probably should've figured it should be something like (3:2)*24mm....
Don't tell Sigma this, they'll start marketing their primes as two-lenses-in-one.
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10-17-2015, 10:55 AM
(This post was last modified: 10-17-2015, 10:59 AM by Rover.)
Quote:Polarisers at such wide angles? Even at 24mm there is usually a very obvious sky gradient effect when used outdoors, unless there are other applications where this isn't a problem?
Suppose the question is, how good is it compared to its nearest rivals? Not something that shows up on MTF, but I'm more interested in their claim of low coma far above absolute resolution (night usage).
Anyone know how to correctly convert the illumination chart to stops? Is it a 2x or sqrt(2) factor per stop?
Generally a stopped down lens will be better than a wide open one. So using a f/4 lens at f/4 will generally not be as good as a f/1.8 lens at f/4. Of course it varies with the specific lenses you compare, and the values may be different.
Guess the 16-35/4 L IS is laughing at all of us. Though, of course, it's an exception rather than rule. But from my experience, lenses like Sigma 20/1.8, Canon 28/1.8, Canon 50/1.4 are all cut from the same cloth - just not really good until stopped down a couple of stops. 28/1.8 couldn't win prizes one stop down, though became somewhat acceptable.
The 24/1.4 L II that I have looks pretty decent wide open - not razor sharp but printable. By the way, it happened to be the lens that captured the final moments of the paper I work(ed) in until yesterday. Just because all the office cameras have already been put under lock and seal to prepare for liquidation, and in I wandered with just the 24 and the 1D Mark IV...
http://nvspb.ru/media/numbers/6078/pdf/12.pdf
To put it on topic... that day I wished it could've been a 20 (or my camera a full frame one). 
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I went straight to Sharpness and then to Summary where the tester concluded with "I think there is nothing left to say…".
Someone will have to explain to me why this doesn't reflect the MTF numbers.
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