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10-08-2009, 05:12 PM   #46
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QuoteOriginally posted by rparmar Quote
It's quite obvious that Pentax does need a contemporary 24mm or 28mm lens at f/2 or faster.
It is quite obvious that Pentax would have to compete with other lens manufacturers on such a market.

If customers only bought Pentax lenses to go with their Pentax cameras then, yes, Pentax would need to address some holes in the line up. However, customers have a wider range to choose from, although I get the feeling that many involved in this thread here are not looking elsewhere at all.

10-08-2009, 06:50 PM   #47
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QuoteOriginally posted by séamuis Quote
so what do you people want exactly? a budget level maybe DAL type 35mm 1.4? like nikons new 35mm? or do you want something higher class but without the price tag? a brand new optical formula? im a bit confused on what a lot of you seem to want from Pentax.
QuoteOriginally posted by Wheatfield Quote
For myself, something in the 30mm range, f/1.4 aperture and a DA Limited lens style build.
..
I want a small carry around standard that fits in between the 21 and the 40mm focal lengths.
Exactly!

I don't subscribe to the argument that such a lens would have to be big and heavy. Firstly, old film SLR 50mm f1.4 lenses were compact - and secondly, isn't the whole idea of a smaller sensor size that lenses can be made smaller and lighter and faster?
(Olympus has certainly proved that to be true - have you seen how fast their lenses are?)
10-08-2009, 07:48 PM   #48
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QuoteOriginally posted by StevenVH Quote
I used quite a few faster lenses in the film days and had a similar reaction when I first looked at the current offerings. Since then I've decided 2.8 is fast enough and when it's not that's what a fast 50 is for. So not much has changed really in that sense from the film days.
The big change since film days is the crop factor. On a DSLR a 'fast 50' becomes a 75mm for all intents and purposes - too long to serve the same function as it once did on a film camera.
10-08-2009, 08:19 PM   #49
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yes, but a 75mm f/1.2 lens would be bloody expensive in the film days..so the older lenses are still eminently usable however the format they are used on has changed.. or you can go full frame.....

10-08-2009, 09:19 PM   #50
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QuoteOriginally posted by Digitalis Quote
yes, but a 75mm f/1.2 lens would be bloody expensive in the film days..so the older lenses are still eminently usable however the format they are used on has changed.. or you can go full frame.....
I think the problem is the flange to focal plane distace. It's around 45mm on the K mount. Anything shorter than that has the rear nodal point outside the lens. The shorter the focal length the more difficult (and expensive) it becomes to put some properties into the design.
A fast 50 is relatively easy. They've been around forever, and can be made relatively cheaply with very high optical quality.
OTOH, a really fast 30ish mm is a different beast.
Look at the specs on Boz's page comparing the fast 28s, or moreso, the M35/1.4 to the M35/2.8.
The difference in size and weight is quite startling.

Now, since it appears that Pentax is on a small, compact lens philosophy, it's quite possible that they just plain can't do a fast normal within the new paradigm.
Not that this explains the DA*55/1.4 which is pretty gargantuan.
10-08-2009, 09:35 PM   #51
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I could swear my fa50mm f1.4 and fa35mm f2 were working perfectly and cost me very little $.
10-08-2009, 10:18 PM   #52
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QuoteOriginally posted by WerTicus Quote
I could swear my fa50mm f1.4 and fa35mm f2 were working perfectly and cost me very little $.
And which one is a 30/1.4?
10-08-2009, 10:33 PM   #53
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Perhaps it's the advancement of technology and I'm presuming that the quality is better....but my 1957 lenses start at F1.9? Why are they all so small? I guess there is autofocus....aperature....advancements in quality.....but I'm not so sure it's better quality after using them.....why does a modern F4 need to have 10X the surface glass to the older f1.9 lenses?

10-09-2009, 01:12 AM   #54
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QuoteOriginally posted by Wheatfield Quote
I think the problem is the flange to focal plane distace. It's around 45mm on the K mount. Anything shorter than that has the rear nodal point outside the lens. The shorter the focal length the more difficult (and expensive) it becomes to put some properties into the design.
A fast 50 is relatively easy.
...
Not that this explains the DA*55/1.4 which is pretty gargantuan.
Had to google "gargantuan"...

QuoteOriginally posted by Spock Quote
Exactly!

I don't subscribe to the argument that such a lens would have to be big and heavy. Firstly, old film SLR 50mm f1.4 lenses were compact - and secondly, isn't the whole idea of a smaller sensor size that lenses can be made smaller and lighter and faster?
(Olympus has certainly proved that to be true - have you seen how fast their lenses are?)
As Wheatfield explains, it is getting complicated to make lenses once you go to a focal length shorter than the registration distance (about 45mm in Pentax case), especially when there is also a mirror to consider. To make a wide angle lens sort of requires breaking some of the basic optical rules (or getting around them), especially if it also has to be a fast wide angle. Some early wide angle SLR lenses required that the mirror was locked up to leave room for the last lens elements. I think the retrofocus lenses were the first way around this, invented for cinema cameras but first applied for SLRs in the 50's by a French lens designer followed by Pentax Auto-Takumar 35mm f2.3 (scroll down), one of the first fast 35mm lenses. A beast with a hugh front element. Despite that the lensmakers now have more tricks in their bag than back in the 50's, such as aspherical lens elements, it is still a challenge to build a fast and/or compact wide angle lens. The DA15ltd is a fine little miracle in it's compactness.

Olympus? You mean their f2 zooms? So hugh that they make the tiny 4/rd cameras look rediculous?

QuoteOriginally posted by smc Quote
Perhaps it's the advancement of technology and I'm presuming that the quality is better....but my 1957 lenses start at F1.9? Why are they all so small? I guess there is autofocus....aperature....advancements in quality.....but I'm not so sure it's better quality after using them.....why does a modern F4 need to have 10X the surface glass to the older f1.9 lenses?
Because they try to correct for abberations, distorsions etc with more lens elements. Optically better lenses. Pentax old 28/3.5 and 35/3.5 are among the sharpest and most distorsin free wide angles I've seen, moderately sized. But if you make it faster the lens elements gets wider, you get more optical problems to correct for, so you need more lens groups, and if we are talking about a zoom, you need to add some group to be able to change the focal length. And some lenses to correct for the optical flaws you creat when you zoom. Then add some electronics and autofocus gears and/pr engines...and the lens is getting rather heavy. The Pentax limited lenses are not the fastest or optically most perfect lenses. But they are miracles of optimized compromises between optical quality and small size, pared with a great build quality. But if the priority is fast lenses, such as the DA* lenses, they at once get bigger.

QuoteOriginally posted by Wheatfield Quote
And which one is a 30/1.4?
Have patience. I think it is comming (you remember the 30mm that was on the lens route and then dissapeared...hopefully that was because Hoya wanted to be more secret, not because we will never see it). Meanwhile, there are other options.

QuoteOriginally posted by Class A Quote
It is quite obvious that Pentax would have to compete with other lens manufacturers on such a market.

If customers only bought Pentax lenses to go with their Pentax cameras then, yes, Pentax would need to address some holes in the line up. However, customers have a wider range to choose from, although I get the feeling that many involved in this thread here are not looking elsewhere at all.
Definitely. And Sigma offers some fast wide angle options. What you will have to live with is some optical flaws (soft corners etc), but you get the speed with their 20/24/28mm f1.8 and 30mm f1.4 lenses.
10-09-2009, 01:57 AM   #55
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QuoteOriginally posted by Douglas_of_Sweden Quote
As Wheatfield explains, it is getting complicated to make lenses once you go to a focal length shorter than the registration distance (about 45mm in Pentax case), especially when there is also a mirror to consider. To make a wide angle lens sort of requires breaking some of the basic optical rules (or getting around them), especially if it also has to be a fast wide angle.
But how is it that Pentax managed to produce a compact 28mm F2 in the 1980s that by all accounts has good optical performance - and cannot do the same today?

It seems strange to me that the only way I could get the focal length speed and compactness I wanted was to go back to a 25 year old lens. Even if the A28/2 that I just bought has some optical compromises in the form of soft corners etc - that shouldn't be such a problem with the DSLR crop factor.
10-09-2009, 02:24 AM   #56
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QuoteOriginally posted by Spock Quote
But how is it that Pentax managed to produce a compact 28mm F2 in the 1980s that by all accounts has good optical performance - and cannot do the same today?

It seems strange to me that the only way I could get the focal length speed and compactness I wanted was to go back to a 25 year old lens. Even if the A28/2 that I just bought has some optical compromises in the form of soft corners etc - that shouldn't be such a problem with the DSLR crop factor.
I have only shot the M28/2 on film looong ago. Perhaps it is not a suitable optical solution for digital due to PF? Then they need to come up with a new solution, which take R&D resources and they have obviously so far prioritised something else. I'm not saying it is impossible, only that it is harder to build a 20/24/28/35 f2 or faster than a 50 f2 or faster. That particular lens is impressive, halft the weight of the K28/2, and one of the M generation redesinges that was getting both smaller and better. Perhaps they will come with their own fast 28 or 30mm eventually. Meanwhile, why not try the Sigma 28/1.8?
10-09-2009, 03:03 AM   #57
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QuoteOriginally posted by Douglas_of_Sweden Quote
Meanwhile, why not try the Sigma 28/1.8?
Because I just bought a A28/2!
10-09-2009, 03:32 AM   #58
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QuoteOriginally posted by Douglas_of_Sweden Quote
Never had any specific autofocus problem with my fast lenses. Of course the DOF is thinner so you get more of the subject out of focus, but that has nothing to do with AF. Probably people are mixing this up.
I don't think so.
While I see what you are saying and totally agree, I do see the other side of the story too.
With the size of the cross type AF sensors on current cameras it is very hard to AF accurately something like 31/1.8 or even 50/1.7 on distance bigger than 2m, unless you don't know (very well) how the AF works, and how the sensors are placed.
This is probably 90% of the reasoning behind me ordering split screen.

BR
Peter
10-09-2009, 05:05 AM   #59
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QuoteOriginally posted by Class A Quote
If customers only bought Pentax lenses to go with their Pentax cameras then, yes, Pentax would need to address some holes in the line up. However, customers have a wider range to choose from, although I get the feeling that many involved in this thread here are not looking elsewhere at all.
The Sigma lenses are no substitute for Pentax quality. They are ugly, heavy, plasticky and have poor performance outside the center unless you stop them down so much that the advantage in maximum aperture is lost. I have never met a Sigma lens I liked as much as a similar Pentax offering. Some of this is no doubt subjective and depends on use.

Nevertheless, the existence of third party lenses does not mean that Pentax do not have a hole in their line-up. That is plain enough.
10-09-2009, 06:24 AM   #60
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Yeah, the absence of fast primes in the current Pentax line up blows significantly.

They are still plenty there in Canon and Nikon land, often at prices cheaper than you'll ever see for a Pentax lens nowadays as well.

They are still needed, especially since Pentax still doesn't do high ISO so well that fast lenses have become irrelevant for Pentax DSLR's.

Pull your finger out Pentax.
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