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04-17-2014, 02:50 PM   #196
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QuoteOriginally posted by Cannikin Quote
DXO lens evaluation/ranking methodology is very poorly thought out by attempting to aggregate all information into some meaningless singular numbers. The most shocking thing to me is this is even their written goal. Very little relevant information can be extracted from them. For instance a lens with a crazy sharp center, but borders with no image at all (blacked out) can still get a high "perceptual megapixel" number on a high megapixel camera. Then there's the fact that they only consider the "best" focal length/aperture combination, so good luck figuring out what it's like at any other aperture. Also, ranking by some arbitrarily defined number is ridiculous, especially for lenses of different focal lengths. They would not be used for the same thing. Give it a personal rating if you want ("5 stars" or whatever) based on how you think a lens of that range should perform, but arbitrary ranking numbers do nothing but fuel nonsense debates like "my 75mm is better than your 24mm". Give us the actual data DXO, kinda like the charts you provide with sensor evaluations. We're big boys and girls, we can handle it.

Anyway, Lenstip now has their review for this lens up: Sigma A 50 mm f/1.4 DG HSM review - Introduction - Lenstip.com. A lot more information you can get out from that.

But again, this isn't coming to K-mount as far as anyone knows, so...
Looks like it'll produce great bokeh circles from that lenstip review.

04-17-2014, 07:16 PM   #197
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Sharpity sharpity sharp!!
04-19-2014, 05:33 AM   #198
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QuoteOriginally posted by Winder Quote
Now if Pentax would redesign the DA* 55mm F/1.4 with a faster AF motor and improve its optical performance.

Or maybe Pentax needs to produce a D-FA* 50mm F/1.2 for the upcoming full frame.
I'd prefer a 55/1.2 (84/1.8 equiv. on APS-C).
04-21-2014, 03:30 PM   #199
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QuoteOriginally posted by Boris_Akunin Quote
I'd prefer a 55/1.2 (84/1.8 equiv. on APS-C).
The 55 f1.4 works on FF already, which makes it a fantastic lens to go between the 85mmish FL and the normal prime FL on 35mm.

But yes, the motor is painfully slow! But I do enjoy using it on my MZ-7 a lot!


One thing I would love is for more DAL primes. faster, plastic, cheapish (sub $500) in 28, 35, 50, 85. Could all be f1.8. Hey, if Nikon can do it with the G series, Pentax should be able to! All FF too.


In other news, I preordered my Sigma 50 for my D800....and I don't know why.

04-21-2014, 04:07 PM   #200
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QuoteOriginally posted by Wired Quote
One thing I would love is for more DAL primes. faster, plastic, cheapish (sub $500) in 28, 35, 50, 85. Could all be f1.8. Hey, if Nikon can do it with the G series, Pentax should be able to! All FF too.
Heavens-ta-betsy!

Pentax has said they're not after lens speed. Your 1.8's in 35/28/85 would be equal to or exceed the 'best' Pentax lenses in/near those focal lengths.

Of course the 50/1.8 already exists; and with the 35/2.4 and 31/1.8 the 35/1.8 is unlikely.

--ElJamoquio, quasher of dreams...

(fortunately all of the lenses above are already FF...)
04-21-2014, 04:09 PM   #201
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QuoteOriginally posted by ElJamoquio Quote
Heavens-ta-betsy!

Pentax has said they're not after lens speed. Your 1.8's in 35/28/85 would be equal to or exceed the 'best' Pentax lenses in/near those focal lengths.

Of course the 50/1.8 already exists; and with the 35/2.4 and 31/1.8 the 35/1.8 is unlikely.

--ElJamoquio, quasher of dreams...

I know. It's very unfortunate that they are using the "ISO is good enough now" argument to not deliver higher speed primes. I'm sorry f4 isn't good enough for live bands sometimes. Even 2.8 can be slow!

But I do love me them FA limiteds!
04-21-2014, 09:10 PM   #202
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If we want professional grade, high speed lenses we are going to have to go for Sigma. Pentax has been clear they prefer small and slow (both aperture and AF).
04-22-2014, 09:52 AM   #203
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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."

They are at least 2-3 notches below the OEMs in terms of build quality.

QuoteOriginally posted by Winder Quote
If we want professional grade, high speed lenses we are going to have to go for Sigma. Pentax has been clear they prefer small and slow (both aperture and AF).


04-22-2014, 04:18 PM   #204
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QuoteOriginally posted by dcshooter Quote
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.
04-22-2014, 05:15 PM   #205
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QuoteOriginally posted by Smeggypants Quote
Sharpity sharpity sharp!!
Like being cut by the most gigantic club around.
04-23-2014, 06:09 AM   #206
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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. To wit:

- Sigma uses plastics for a lot of comonents where OEMs (Pemntax/Nikon/Canon/Olympus) use metals. This includes critical components like focusing gears.
- 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
-Where screws are used, their quality tends to be lower - Sigmas tend to strip out much more readily than those used by the OEMs
- overall mechanical tolerances and fit appear to be generally poorer
- Sigma is notorious for not licensing communications protocols, but rather reverse-engineering them. 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.
- The exterior paints and finishes used on Sigma lenses are low quality and are notorious for chipping, flaking, and degrading.

While on the one hand, it is understandable that a company such as Sigma who is interested in underselling the OEMs might focus on optical quality to the detriment of other aspects of lens construciton, interestingly, on the other hand, these problems are not nearly as bad in lenses produced by Tamron.

As stated before, I have not worked on the ART line, but I have worked on several DG line lenses, most recently the 50mm Macro, the Bigma (with HSM), the 70-300mm APO, and the 10-20mm. This is not to mention various other Sigma lenses I have worked on over the years from all periods of its history. These problems have been ubiquitous.

By comparison, the Limited lenses really are the gold standard in construction for AF lenses these days and most closely resemble the robust lens designs of the 1970's (albeit with some necessary compromises mad ein order to enable AF operation). SDM aside, the * lenses are actually quite well made as well and stack up well against the pro level offerings from Canon and Nikon. Even the plasticky Pentax kit lenses these days are quite nicely built, especially compared to what Pentax (and everyone else for that mater)was producing at the end of the film era.

QuoteOriginally posted by Class A Quote
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.
04-23-2014, 07:04 AM   #207
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QuoteOriginally posted by dcshooter Quote
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.

QuoteOriginally posted by dcshooter Quote
- 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".

QuoteOriginally posted by dcshooter Quote
- 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?

QuoteOriginally posted by dcshooter Quote
- 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.

QuoteOriginally posted by dcshooter Quote
- 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.

QuoteOriginally posted by dcshooter Quote
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".

QuoteOriginally posted by dcshooter Quote
- 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.
04-23-2014, 07:15 AM   #208
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QuoteOriginally posted by Class A Quote
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.
04-23-2014, 09:05 AM - 2 Likes   #209
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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
04-23-2014, 09:22 AM   #210
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QuoteOriginally posted by ElJamoquio Quote
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.
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