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02-28-2014, 09:20 PM   #1
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Fast lens for Pentax (thoughts from Sigma 18-35 F1.8)

I think for APS-C lenses, it is high possible to build 16-50 F1.8/50-150 F1.8 in the same weight of a FF 24-70/70-200 F2.8 lens. The only reason the manufactures do not have make them is that they thought APS-C camera market is low/middle-end markets, which targets typically do not want to spend $2000 on one len.

Sigma made the first step to deliver 18-35 F1.8.. The most important reason they made 18-35 instead of 16-50 is to control the price& weights, otherwise it will be a $2000+ monster where the APS-C buyer will merely spend that much money on a single len.

At the prime side, Pentax for sure can deliver some fast APS-C lens such as 24mm F1.2/35mm F1.2/50mm F1.2/85 F1.2 (their size will still be smaller than FF lenses as 85 F1.2 APS-C only lens will surely be smaller than a FF 85 F1.2). The price will also be lower and at the $1000-$1500 level instead of $2000+ level.

However, it is just a dream as Pentax apparently sticks with the portability on APS-C region and does not have strong motivation to challenge itself due to small market share. And as far as we know, lot of pentax prime lens are in fact ff compatible lens, which simply means that they are lazy to design as a lot of lights are wasted!

To be more precise of this above idea, I just pick up Fuji as example: Fuji has a new released XF 56/1.2 . It is a prime portrait-length lens that provides a 35mm-equivalent focal length of 85mm. Comparing to 1025g and $2200 pricing for Canon 85mm 1.2, Fuji 56/1.2 is $999 (new price) and only 405g. Apparently APS-C 85mm 1.2 can be much lighter and weighter than the FF equilvalent under the same max aperture. Fuji has already released 23/1.4 (301g, $749 in BH) and 35/1.4 (184g, $449 in BH). In Pentax's side, a close look up of prime lenses gives 21/3.2(119g, $696 in BH (HD version)), 35mm/F2.0 (196g, $399 in BH) and *55/1.4 (376g, $796 in BH). So in princple, pentax can easily make 21/1.8, 35/1.4 and 55/1.2 with slightly increase of weight and maintain at the same price range. Apparently pentax looses the ground for portability comparing to mirrorless (MF, APS-C and FF) as the world of digital photography is evolving. For example, the full load weight of Fuji X-T1 + 23/1.4 is 740g while the pentax K5-ii (I will not use K-3 here) + 21/3.2 is 859g. Many young peoples, who love portability but have no preference between DSLR and mirrorless, will not consider the pentax. If Pentax/Roich will stick to APS-C line, they should seriously consider how they can hold its own place under FF and mirrorless. It is a possible crisis to Pentax. One of possible reasons is that they have anticipated that FF will gradually dominate even the consumer level DSLR market, (which is highly possible to occur in next 3-5 years), they have to put their resource and priority to prepare and release FF or FF mirorrless camera/lenses.

Okay, the topic moves to Pentax Full frame... :-( Anyway, my point is that the whole prime lens of Pentax are FF competitible more or less, it is a huge waste. Even if Pentax released FF camera, they should seriously consider release fast but inexpensive APS-C lens (APS-C version 30F1.4, 55F1.2, 85F1.4 et al) . If they can control the prices below the current ridiculous high HD DA lens, there will be a really sale boost and benefits also our pentaxians... Not to mention fast APS-C zooms.... Fast with compactness, that's the place APS-C lens can win FF lens.


Last edited by starjedi; 03-05-2014 at 08:23 PM.
02-28-2014, 09:22 PM   #2
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I'm not a fan of primes like most here, but I'd consider fast zooms.
02-28-2014, 09:27 PM   #3
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QuoteOriginally posted by VoiceOfReason Quote
I'm not a fan of primes like most here, but I'd consider fast zooms.
I can see it from your portfolio! :-)
02-28-2014, 09:32 PM   #4
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QuoteOriginally posted by VoiceOfReason Quote
I'm not a fan of primes like most here, but I'd consider fast zooms.
Fast zooms can never really compete equally with primes of equivalent or faster apertures.

02-28-2014, 09:35 PM   #5
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In my experience primes aren't all that everyone makes them out to be. But hey, that's just my style of shooting! I've sold most of the primes I've had because they weren't as good as what I had with other things. I've sold off various 50s from f/1.4 to f/2.0, a 20 f/1.8, a 35 f/2.8. I like the couple I have, but none of the others impressed me or weren't useful for what I do.
02-28-2014, 09:48 PM - 1 Like   #6
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Well that is where we are different - with APS-C and FX format there are some decent f/2.8 zoom lenses but these frequently get owned by primes that are often smaller - and faster than the zoom lens in question ( Canon EF 24-70L vs 24mm f/1.4L, Nikkor 70-200mm f/2.8G ED VRII Vs 200mm f/2 G ED VRII, Pentax DA 20-40mm f/2.8~4 Vs FA31mm f/1.8 ASPH Limited - No contest). There are zoom lenses for medium format, but they tend to be considerably heavy even though their widest aperture is f/5.6, they still to be stopped down to get the most out of them. As the formats get bigger, primes lenses are the only choice for 4X5 and 8X10.

Zoom lenses have their place, some of them perform so well in terms of image quality that at certain apertures they are almost indistinguishable from a prime. Zoom lenses are convenient, they are cost effective by virtue of giving a variety of focal lengths to work with - but because of this they are inherently compromised.

Last edited by Digitalis; 02-28-2014 at 09:53 PM.
02-28-2014, 09:51 PM   #7
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QuoteOriginally posted by Digitalis Quote
Well that is where we are different - In 35mm there are some decent f/2.8 zoom lenses but these frequently get owned by primes that are considerably smaller - and faster than the zoom lens in question. There are zoom lenses for medium format, but they tend to be considerably heavy even though their widest aperture is f/5.6, they still to be stopped down to get the most out of them. As the formats get bigger, primes lenses are the only choice for 4X5 and 8X10.

Zoom lenses have their place, some of them perform so well in terms of image quality that at certain apertures they are almost indistinguishable from a prime. Zoom lenses are convenient, they are cost effective by virtue of giving a variety of focal lengths to work with - but because of this they are inherently compromised.
Yes. For example, if we have 18-35mm, which means that we put at least three primes in camera at the SAME time: 18 F1.8, 28F1.8 and 35F1.8. More interestingly, as we learned, the IQ of 18-35mm is even better than many of primes around this range!
02-28-2014, 09:51 PM   #8
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I don't shoot any medium or large format, so I will take your word on that. I couldn't afford to shoot those formats. Still, looking at the reviews on the new Sigma 18-35 f/1.8 it seems as if it is pretty much owning primes in that range. That also happens to be the range I do most of my indoor stuff in, so it is perfect for me.

02-28-2014, 10:00 PM   #9
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QuoteOriginally posted by starjedi Quote
IQ of 18-35mm is even better than many of primes around this range
It also pays to note that the sigma 18-35mm f/1.8 isn't exactly a small or light lens, Primes of 18,24 and 35mm with equivalent f/1.8 apertures would be smaller and the practical upshot of this is the lenses will have smaller filter threads. The sigma Zoom also has the famous sigma "onion ring" bokeh, it is also less flare tolerant than prime lenses are, Coma and astigmatism are also problematic at wide apertures.

Last edited by Digitalis; 02-28-2014 at 10:10 PM.
02-28-2014, 10:28 PM   #10
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QuoteOriginally posted by Digitalis Quote
It also pays to note that the sigma 18-35mm f/1.8 isn't exactly a small or light lens, Primes of 18,24 and 35mm with equivalent f/1.8 apertures would be smaller and the practical upshot of this is the lenses will have smaller filter threads. The sigma Zoom also has the famous sigma "onion ring" bokeh, it is also less flare tolerant than prime lenses are, Coma and astigmatism are also problematic at wide apertures.
:-). Yes. That 's why I say it means we put three primes in camera for 18-35... We put three at the same time...
02-28-2014, 11:21 PM   #11
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You must understand that primes till 84mm are smaller than fast zoom. It's possible to build 18-50mm f1,8 but it will be gigantic
03-01-2014, 12:22 AM   #12
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QuoteOriginally posted by starjedi Quote
Yes. For example, if we have 18-35mm, which means that we put at least three primes in camera at the SAME time: 18 F1.8, 28F1.8 and 35F1.8. More interestingly, as we learned, the IQ of 18-35mm is even better than many of primes around this range!
This may be the case with the Sigma 18-35. For example, it wouldn't be hard for it to beat all Sigma primes in this range! But to beat the FA31/1.8, or most of the Canon/Nikon/Sony 35 or 24mm f/1.4 lenses - I don't think so! It may not even beat the cheaper Samyang 24/1.4, for all I know.


A rare exception to the rule is the Nikon 14-24/2.8. It seems to beat any current primes I can think of at its wider end. But this doesn't preclude someone creating, for example, a superior 15/2 in the future!
03-01-2014, 03:13 AM   #13
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QuoteOriginally posted by VoiceOfReason Quote
In my experience primes aren't all that everyone makes them out to be. But hey, that's just my style of shooting! I've sold most of the primes I've had because they weren't as good as what I had with other things. I've sold off various 50s from f/1.4 to f/2.0, a 20 f/1.8, a 35 f/2.8. I like the couple I have, but none of the others impressed me or weren't useful for what I do.
I think you've been using the wrong primes! For example, the 20/1.8 must be the Sigma, which is an absolute joke when it comes to border performance within 2 stops of wide-open - even on APS-C! And the overall IQ doesn't look too good either! While I mostly rely on the appearance of images taken with a lens, photozone's measurements can be a good starting point for understanding the differences among lenses. And many of the Sigmas are seriously deficient through the 2 widest stops or so, where a quality prime should actually shine! Sigma AF 20mm f/1.8 EX DG RF (DX) - Review / Lab Test Report - Analysis

The Sigma 24/1.8 and 28/1.8 have similar problems, as well as other not-as-closely-related lenses such as the Sigma 30/1.4.


So don't judge primes based on the worst examples out there.


Examples of lenses done right would be the FA31, the Canon 35/2, the Canon 35/1.4, and the Sony Zeiss 24/2:

Pentax SMC FA 31mm f/1.8 AL Limited - Lab Test / Review - Analysis
Canon EF 35mm f/2 USM IS - APS-C Format Review / Test Report - Analysis
Canon EF 35mm f/1.4 USM L - Review / Test Report - Analysis
Zeiss Distagon T* 24mm f/2 ZA SSM (SAL-24F20Z) - APS-C Review / Lab Test - Analysis


And then lenses that come awfully close for a low price:

Pentax SMC DA 35mm f/2.4 AL - Review / Lens Test - Analysis
Sony 35mm f/1.8 DT SAM ( SAL-35F18 ) - Review / Test Report - Sample Images & Verdict
Nikkor AF-S DX 35mm f/1.8 G - Review / Test Report - Analysis


Also keep in mind that, by design, even a quality zoom almost has to be compromised within the first stop of wide-open. In comparison a quality prime can be strong within the first stop. And given that quality primes are typically 1-2 stops faster than quality zooms to begin with, in terms of usable speed primes can offer over a 2 stop advantage. Even the cheap $200 primes above can offer a 1-2 stop advantage. But lenses like the Sigma 20, 24, and 28mm f/1.8s may not even match the zooms, let alone beat them! This is why Sigma's turning over a new leaf - because they had to. People got tired of being sold "value-priced" lenses that were designed (apparently for marketing reasons) with much faster apertures than they could effectively be used at.

Last edited by DSims; 03-01-2014 at 03:19 AM.
03-01-2014, 04:07 AM   #14
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Although zooms will never overcome primes in terms of quality, they will still work good enough for the majority of photographers
03-01-2014, 04:24 AM - 1 Like   #15
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QuoteOriginally posted by Dariusz Quote
Although zooms will never overcome primes in terms of quality, they will still work good enough for the majority of photographers

That's the problem at issue here - for fine art photographers good enough doesn't cut it. There are also certain specialist areas that zoom lenses can never compete with prime focal lengths: Macro photography, fast super telephoto lenses, Tilt/Shift lenses and high speed lenses (f/1.2 and faster) - zooms will never encroach on these areas because of they are inherently compromised.

Certainly I work with Zoom lenses - however I do so because in some situation I simply have no other choice. I recognize their limitations, but if I had to choose between a 16-50mm f/2.8 or a 50mm f/1.2, I would take the fast fifty.

Last edited by Digitalis; 03-01-2014 at 04:33 AM.
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