[Class A]

I don't know about the present generation of ART lenses, but having looked at the internals of even some very recent Sigma lenses, I can tell you that aside from optically, they are defintely not "professional grade."

Can you please elaborate to which lens models you are referring to and which other, professionally-grade OEM lens models you are comparing them to?

One certainly hears significantly less about (HSM) AF failures on Sigma lenses compared to (SDM) AF motor failures on Pentax lenses. On many lenses Sigma uses a ring motor type which is a lot more robust than the micro motors used for SDM.

[Aristophanes]

Sharpity sharpity sharp!!

Like being cut by the most gigantic club around.

[Class A]

The SDM motor I'd say is a special case ( and a bit of a red herring, since the previous posts were taliking about the Limited lenses with screw drive, not the * zooms). I am talking more about general quality of construction and materials being used.

Pardon? A "red herring"?

The SDM issue is not a "red herring", it fundamentally relates to what makes a lens "professional grade" as the latter particularly entails reliability. The SDM issue is a big problem, it must have cost Pentax numerous sales and a lot of reputation.

I do not see a substantial discussion focused only on "Limited lenses" and the post from Winder you responded to just made a very general statement about "professional grade, high speed lenses"; it was by no means reducing the context to Limited lenses.

I suspected that you did not really have convincing arguments regarding Sigma producing second-grade lenses and your response did not convince me otherwise.

- Sigma uses plastics for a lot of comonents where OEMs (Pemntax/Nikon/Canon/Olympus) use metals. This includes critical components like focusing gears.

Don't we all emotionally respond to metal whereas rationally we should acknowledge that often modern synthetic material is the better choice?

Synthetic material can be more temperature stable, respond better to knocks, can be manufactured to meet lower tolerance requirements, etc.

I guess we should all avoid Pentax DSLRs because the material directly behind the metal bayonet that is crucial for robust mounting with optical precision is an example of using "plastics".

- Sigma will often tape components together where others will use set screws. Structurally, this need not be a problem, but in hot temperatures, the adhesive can soften and things loosen up

I know that they have done that in the past with their cheap budget lenses.
Can you provide an example of an inadequate use of tape in an EX series lens, for instance?

- overall mechanical tolerances and fit appear to be generally poorer

I don't think your impression ("appear") counts much.

Many Pentax lenses have mechanical issues. The 16-50/2.8 was plagued with decentering; DPR could not find one in three DA* 55/1.4 without an optical issue, a PF users went through five copies and still couldn't find a satisfactory one. Even the FA 31/1.8 is notorious for having a loose front group (hood wobbles) or a loose middle group (wobbles when you shake the lens) or both. An FA 31/1.8 without issues is a fantastic lens, but there are many copies around which do not achieve the intended performance because of manufacturing tolerances.

I'm not trash talking Pentax lenses (although I wish for the price you are paying for an FA limited the QC would be better) but it is simply not true that Pentax build is beyond reproach while Sigma uses cheap parts.

- Sigma is notorious for not licensing communications protocols, but rather reverse-engineering them.

This has no relevance to the topic at hand.
I guess the use of "red herring" would actually be appropriate now.
It seems like you have a bias against Sigma to which you are of course entitled.

The problem is, when newer bodies (particular Sonys and Canons) have come out, they have been unable to communicate with legacy glass. Sigma has on occasion re-chipped lenses, but they have not done so for every model, and they generally will only supply the service for a shor ttime.

I have had an out-of-production lens serviced by Sigma with no issues. On this forum, I have heard many praises for Sigma service with chips being exchanged for free and with quick turnarounds. I cannot remember one story where a user was turned down because their lens was only "serviced for a short time".

- The exterior paints and finishes used on Sigma lenses are low quality and are notorious for chipping, flaking, and degrading.

I do not know which Sigma lens models you are talking about.

My EX series lenses do not exhibit any of these problems.

To get back to the term "professional grade": Many pros use Sigma lenses. Lindsay Adler is a prominent example. She uses Sigma lenses exclusively on a Canon camera. I'm sure she is paid by Sigma, but I do not believe that she would have accepted the deal if the lenses were not fit for professional use.

[ElJamoquio]

Synthetic material can be more temperature stable

I'd have to see the specs on the plastics used to believe it.

Generally polymers have far more temperature growth. Even the glass-filled stuff generally brings it down to 'just' near-metal stability.

I agree with your point overall but this one is a little iffy.

[robbiec]

Lots of arguing over a lens that is probably the 2nd best overall in the 50s segment if sharpness / speed is your thing. If factors such as cost / value and sharpness then probably the best as its only competitor realistically is the Zeiss Otus which is over 3 times more expensive and MF only. Compared to the Pentax line up, it does highlight a certain laziness in lens development as realistically our lenses (Pentax) do not compete at this tier of optical ability. If I was setting out to refresh my lens line up I would go the following route, DA15, Sigma 18-35, Sigma ART 35, Sigma ART 50 (if it ever becomes available on K mount), FA77 Limited, DFA100 Macro. Arguments could be made for the FA31 instead of the ART 35 but no arguments could be made for the DA50 (built to a price, no DOF scale, plasticy), FA50 f/1.4 (too soft and lacking contrast until f/2 - even when augmented with a hood) or the DA*55 (too slow to focus and not designed as a flat 50 but a rounded 50 with pretensions to being an 85). So out of 6 lenses, 3 are Sigma and 3 are Pentax, 2 are based on old designs and are lacking modern features and the DA15 is probably the best new design Pentax has released over 10 years. Sigma on the other hand have 3 brand new designs which are either ground breaking (f/1.8 zoom) or near as dammit best in class even if cost is no option.
Quality wise I have heard no horror stories about the build of these ART series, they might lack the tactile delight of an FA Limited's aluminium or have the great hood design of a DA* but the are equal to or better than class best. I say this competition in the form of Sigma optical design is the mostly unheralded game changer for this industry. For too long the big players have played safe optically, rehashing old designs over and over, their time is now up and I would say that lens designers all over are frantically working around the clock with designs to get them back into the playing field. It used to be that Pentax had great optics and crap cameras, now it is the other way around

[Class A]

I'd have to see the specs on the plastics used to believe it.

I didn't really mean to say that the thermal stability is better than metal, sorry.

I believe I was thinking about the "Thermally Stable Composite" that Sigma uses. It has the same level of shrinkage as Aluminium with very good elasticity, so it seems like a high-tech (as opposed to "cheap") material to me.

BTW, there are many OEM lenses from respected manufacturers that use "plastic" internal lens mounts.

[ElJamoquio]

I didn't really mean to say that the thermal stability is better than metal, sorry.

I believe I was thinking about the "Thermally Stable Composite" that Sigma uses. It has the same level of shrinkage as Aluminium with very good elasticity, so it seems like a high-tech (as opposed to "cheap") material to me.

BTW, there are many OEM lenses from respected manufacturers that use "plastic" internal lens mounts.

No arguments with any of those statements.

[Belnan]

_______________________A 50 1.4___________________________________________________________ FA 43 1.9___________________


It seems Sigma is producing lenses that are far more appealing from a marketing point of view than other companies. They focus on sharpness at wide open as opposed to peak sharpness. I am not saying their lenses are not good but other companies realise that there are trade offs. Maybe in this day and age of pixel peeping and dxo mark scores that is what other companies should be focusing on as well not just the photo's they produce. Compared to the FA 43 the sigma is slightly sharper below 2.8 above that the aging pentax clearly beats it in center resolution or am I reading these incorrectly?

[Dice]

It seems Sigma is producing lenses that are far more appealing from a marketing point of view than other companies. They focus on sharpness at wide open as opposed to peak sharpness. I am not saying their lenses are not good but other companies realise that there are trade offs. Maybe in this day and age of pixel peeping and dxo mark scores that is what other companies should be focusing on as well not just the photo's they produce. Compared to the FA 43 the sigma is slightly sharper below 2.8 above that the aging pentax clearly beats it in center resolution or am I reading these incorrectly?

It is hard to derive any solid conclusions with regards to which has better resolution from the two graphs because they were likely shot from two different cameras with different sensors. More to your point, I do believe Sigma is capitalizing on consumers obsession (and perhaps misguided perception) that best numbers=better photographs. However it does, if nothing else, give the owner bragging rights for the sharpest ...... around for a short time before it is bettered by the next best lens.

[gazonk]

But.... The bulk!! Mount this lens on a d800 and the combo weighs the same as a 645z with a longish normal... (The 75/2.8)

[ElJamoquio]

The d800 would be faster. The 645 could be sharper... but that 75 is older so who knows.

Let's say in a perfect world the d800 is a stop and a half faster and the 645 is sharper.

Choose your poison.

[gazonk]

If you want razor sharp, you need to stop down anyway if your subject isn't completely flat ;-) I never had faster than a 50/1.7 on FF (i.e. film) and only very occasionally used f-stops below 2.8.

This lens seems like a perfectionist engineer's dream more than a photography tool to me. I'm sure it will be used to take wonderful pictures, but if one is ready to accept this amount of bulk in trade for IQ, an MF system seems more tempting. Except for the price tag, of course.

[Winder]

I shoot mostly events and spend most of my time at F/4 or faster. I don't use flash and I want all the speed I can get. Working a crowded room or a stage with a busy background I want to melt away the distractions as much as possible since I can't control my background.

I want speed and sharp usable images at wide apertures. The size and weight at not really that much of an issue.

[Ubuntu_user]

I will own this lens... If it's anything like my Sigma Art 35mm f/1.4

---------- Post added 05-15-2014 at 04:51 PM ----------

Seriously, the quality (at least of my 35mm) is stellar. I've taken it through rain storms and all kinds of abuse and it just keeps delivering the goods. Sure, it's a heavy beast, but I guess I'm willing to endure that for the quality. I've had my fair share of non-art Sigma lenses, and even the best of them don't come close to the quality, both physical and IQ, of the 35mm art lens... The consistency of what it delivers beats any Pentax lens I've ever owned, though I have had Pentax lenses that best it in terms of occasional output.
If this latest 50mm release is the same... It's worth the weight, and size, and price.

But that's just my opinion.

[Poit]

I shoot mostly events and spend most of my time at F/4 or faster. I don't use flash and I want all the speed I can get. Working a crowded room or a stage with a busy background I want to melt away the distractions as much as possible since I can't control my background.

I want speed and sharp usable images at wide apertures. The size and weight at not really that much of an issue.

Amen!

---------- Post added 05-16-14 at 06:11 PM ----------

Seriously, the quality (at least of my 35mm) is stellar. I've taken it through rain storms and all kinds of abuse and it just keeps delivering the goods. Sure, it's a heavy beast, but I guess I'm willing to endure that for the quality. I've had my fair share of non-art Sigma lenses, and even the best of them don't come close to the quality, both physical and IQ, of the 35mm art lens... The consistency of what it delivers beats any Pentax lens I've ever owned, though I have had Pentax lenses that best it in terms of occasional output.
If this latest 50mm release is the same... It's worth the weight, and size, and price.

But that's just my opinion.

I agree, so I guess it's not JUST your opinion