[Scythels]

I am wondering why the mirrorless lenses are generally less "harmonic" than the DSLR designs. 

I would imagine that it is partly forced due to the register distance and digital medium, in lenses which are either symmetric or ultra-wide angle designs they essentially must make the lens rearside telecentric - meaning the chief ray travels roughly parallel to the optical axis instead of hitting the sensor at an angle.  Here you see a 12mm f/1.2 lens for roughly 1" chips:

 

http://i.imgur.com/4y51FxB.jpg

 

The green ray bundle originates off-axis and travels to the edge of the sensor - clearly it is the chief ray (I would know since I optimized this lens, but I am trying to clarify as I often reference the chief ray and I am not sure people know what it is).  The center ray of the bundle is the 'actual' chief ray.

 

See how the angle at which light approaches the sensor is slight?  that means this lens is 'nearly' or 'somewhat' telecentric.  If the center green ray were a straight line parallel to the dot-dashed line it would be a truly telecentric lens. 

 

Because the rear element diameter will rival the size of the sensor, you are forced into a nearly telecentric design space.  Due to the troubles with digital chips and obtuse angles, it would be natural to just go all the way.

 

But a telecentric design forces several potentially nasty conditions on the design, so you lose degrees of freedom to optimize with.

 

There is also the question of size- take the 12mm f/2 from olympus for example.  If you scaled that lens to FF you would genuinely have a 24mm f/2 without changing anything but the size of everything.  However, the increase in rho by a factor of 2 would enormously increase aberrations with dependency on rho and you would likely become staunchly limited by 5th order aberrations. 

 

Anyway, that lens is quite small.  In an academic or research sense it is often easily possible to produce a diffraction limited design (I would ignore most people using the phrase diffraction limited online - photographic lenses are very rarely DL).  The trouble is the many many restrictions imposed physically.  You want the rear element +=2mm from the flange distance to avoid an excessively long lens, but it physically cannot get too close.  You have unfair restrictions placed on you for lens diameter and length.  You are also limited in the materials you may use by price or availability.  Here is an abbe diagram:

 

http://upload.wikimedia.org/wikipedia/co...iagram.png

 

If you find BK7, that is usually the left termination point.  BK7 happens to be super easy to make and is very common - it is the cheapest materials and most materials are listed in the catalog as a multiple of the price of BK7.  When designing lenses, the left cap for glasses that are allowed is usually BK7 - beyond that is the "low dispersion" realm where glasses cost 60x+ what BK7 does. 

 

On the other side there is LaSF.  LaF materials are fine generally.  LaSF are hard to make and hard to work with.  They are fragile and universally 100x+ the cost of BK7.  If you use them they quite literally drive the discussion regarding price of the lens.

 

Restrictions like these physical and material ones cause photographic lenses to often be not as good as we'd like.  Cinema lenses have many of these problems relieved through much larger bodies and much higher prices. 

 

I will reply more later - class soon.

 

Still, the distortion is very disappointing.  Canon's 16-35 is equivalent but has values of rho much larger and a larger field while having a better correction without costing much more.

 

edited to add more:

 

the tl;dr of above is that there are more constraints in mirrorless lens design (which is quite ironic, as the removal of the mirror removes one constraint but the mechanics and packaging add more than the one taken away).

 

The additional constraints hurt the design by limiting what can be corrected.

 

The sensor could contribute to the vignetting and definitely does contribute some, as sensors always will, but I am skeptical that the vignetting is not mostly optical.  Vignetting is a 'valid' corection mechanism for corner performance if the customer or designer is okay with a loss of energy at the edge of the detector.

[Klaus]

Is the center noticably (visually) softer @ 24 than the other vocal lenghts (2650 vs 3050) ?

 

Well, you will see a hint of softness compared to the cracking sharpness at the other focal lengths.

Nothing to be worried about though.

[Rover]

"Not always very useful" is answering what, exactly?

F4 compared to f5.6 is not very useful a difference on APS-C with an UWA zoom, in my opinion. You are not gaining a lot of shallow DOF (to say it mildly) and exposure time wise it is still an UWA anyway.

 

I too have had the crappy put together Tokina 12-24mm f4 (which would have worked just fine on that APS-H camera) and do not get why its constant f4 would be of any advantage.

 

And that is not worth €600 or €731 to me.. 

Stupid quotation system. "Not always very useful" was quoting yourself, and it was the second question. The first one you asked was why the price was higher than comparable Canon EF-S and EF-M options, and then you said  the Fuji has a bigger focal range than both and is constant f4 which is a part of explanation. Not to mention the better build quality of the Fuji vs. the EF-S.

 

The Tokina does not play exactly well with APS-H sensors, it only starts working without heavy vignetting almost halfway through the range -- I tried.

 

Re: the shallow DOF... it's not be all end all of photography. A lot of the times... quite the opposite. That's not something I would really want in an ultrawide anyways - maybe there are some very specific usage cases, I can't think of any that would benefit me in my work. You could probably get what you want anyways by focusing close.

[Brightcolours]

Stupid quotation system. "Not always very useful" was quoting yourself, and it was the second question. The first one you asked was why the price was higher than comparable Canon EF-S and EF-M options, and then you said  the Fuji has a bigger focal range than both and is constant f4 which is a part of explanation. Not to mention the better build quality of the Fuji vs. the EF-S.

 

The Tokina does not play exactly well with APS-H sensors, it only starts working without heavy vignetting almost halfway through the range -- I tried.

 

Re: the shallow DOF... it's not be all end all of photography. A lot of the times... quite the opposite. That's not something I would really want in an ultrawide anyways - maybe there are some very specific usage cases, I can't think of any that would benefit me in my work. You could probably get what you want anyways by focusing close.

A higher price is reasonable, I question the amount of higher-ness. The FF Canon L is in the same ballpark, which makes the Fuji price look even more excessive. 

I know the Tokina can't be used at 12mm on the 1D APS-H, but it can well be used with it and give a similar wide FOV as it gave with your APS-C camera (at about 15mm)  (and also can be used on FF at about 18mm). That was my point... 

 

Why is constant f4 with an UWA a big plus for you, what constant f5.6 won't give?

[felix]

Hm.. Prices are a funny thing because there are so many things that influence them and the market - as in demand and supply - probably plays a rather limited role in the case of lens pricing (it is a very rigid/imperfect market from a theoretical point of view). Therefore, it is difficult to make cross-comparisons of lenses for different systems made by different manufacturers based on optical design and performance. Yet we still do it a lot - including myself


Regarding the Fuji 10-24: It may be a pricey lens and probably excessively so, but that is actually part of Fujifilm's strategy (and Olympus' and Sony's with FE). Their target customers are (mainly) men who are 40-60 years old and make 100.000$+ a year (these numbers are from an interview with an Olympus sales rep who was talking about the OM-D line, which is Fujis main competitor). So, Fuji probably doesn't want to deliver the best bang for the buck, because they don't need to. Which is really kind of a shame for Fuji users like me.. or Klaus

The Canon 10-18 STM and the Tokina lenses are targeted at a very different audience and therefore priced more competitively.

[dave9t5]

I for one rarely shoot over f/4 with wide angles.  Faster apertures make plenty of sense on wide angle, if not more.  Long lenses have plenty of shallow DOF.  Wide angles have trouble limiting DOF, so the faster the better please in order to isolate subjects.  

 

Most WA zooms have poor min. focussing distance so I stick with primes.  Getting closer is another way to gain WA subject separation.

 

15mm f/4:



 

14mm f/4:



 

10mm FE f/3.5:



 

10mm FE f/4:



 

 

Hmm, a lot of drink photos....here's a non-drink photo:

 

15mm f/4:

[dave9t5]

Beside shallow DOF, sometimes the advantage of bright lens is that it's just plain dark!

 

15mm f/4 1/6sec (hand-held...Pentax IBIS, heh heh):

 

[stoppingdown]

Agreed.

[Rover]

A higher price is reasonable, I question the amount of higher-ness. The FF Canon L is in the same ballpark, which makes the Fuji price look even more excessive. 

I know the Tokina can't be used at 12mm on the 1D APS-H, but it can well be used with it and give a similar wide FOV as it gave with your APS-C camera (at about 15mm)  (and also can be used on FF at about 18mm). That was my point... 

 

Why is constant f4 with an UWA a big plus for you, what constant f5.6 won't give?

1. Fuji is... Fuji. They seem to stick with the higher-end impression and keep their users stuck with that, so maybe they thought they could get away with some extra margin.

2. Ah, that's called "hindsight"... I sold the Tokina and got the Canon 17-35L thinking that my first 1D would follow shortly... but the old 30D stuck for a year more (not that I would complain too much... better that camera than none at all).

3. F4 seems like a nice balance between speed and usability (as in bulk/weight/cost), especially with today's higher available/usable ISO. I'm contemplating the switch from 16-35/2.8 to 16-35/4 IS for that reason: I almost stopped needing f/2.8 in that range, and I have a 24/1.4 anyways for when I do, but the quality of the /4 seems a bit nicer (and the darnable hood is a lot smaller!) This Fuji 10-24 we're discussing looks like a carbon copy of the 16-35/4, only for APS-C (and the notion has suddenly become fashionable, with 3 sloer 16-35s on the market, all from different companies).

[Scythels]

The 10-24 might be a spec copy, but the lens design of the 16-35 and the 10-24 are only similar in that they are retrofocus lenses.