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05-28-2020, 09:37 AM - 2 Likes   #556
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QuoteOriginally posted by willdmo Quote
Two indications.
You can't break physics that's why a given front lens diameter translates to a maximum possible aperture, but with a focal length of 21mm, F/1 can theoretically be reached at 21mm lens diameter. So this helps nothing here, however, the depth of field scale starts with F/4 left and right the red middle line. Lines to the side are always stopped down results. This proves the lens is faster than F4 but not Faster than F2.3, otherwise this lines would start with F/2.8. Everything else is speculation but it is likely something around F/3 +- 0.3
  1. The 'physics' you are referring to applies to the diameter of the entrance pupil, not to that of the first lens element. The two diameters are the same only in the case of long lenses. They are quite distinct as far as (retrofocus) wide angle lenses are concerned. There is no usable rule in the specific case of the D FA 21mm Limited.
    ---
  2. Any and all Pentax K mount lens with an aperture larger than f/4 have a 4 as first mark, irrespective of their maximum aperture.


05-29-2020, 12:41 AM   #557
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It will have to be f/2.
Again, the good comparison is with FA*24/2 and i don't see any interest if slower.
05-29-2020, 12:58 AM   #558
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QuoteOriginally posted by Zygonyx Quote
It will have to be f/2.
Again, the good comparison is with FA*24/2 and i don't see any interest if slower.
There is coming DFA*24/1.4 for you
05-29-2020, 01:30 AM - 2 Likes   #559
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As a PSA ... several 35/2 lenses to see the differing constructions ... from left to right : STak 35/2, SMC Tak 35/2, SMC K 35/2, SMC M 35/2.

After, there's an image of a Minolta MD 35/1.8 and a Vivitar 35/1.9 (M42).

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05-29-2020, 03:29 AM   #560
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Okay people. you proved me wrong to some point, The Lines with for cant be used to judge how fast the lens can be, except for that it is faster than F4, otherwise the markings would need to start with a higher number like 5.6 (unlikely) or F8.
Given the looks, it is more a hefty of a lens than the other limited lenses and therfor can be faster, on the other hand the really fast lenses are more expected in the ★ lineup.

I think what we know for sure is:
The lens is faster than F4
And everything else was already in their press release:
It is a 21mm lens without aperture ring so basically useless on all film bodies without dial for apertures
The lens has no screwdrive AF (no AF at all on analog cameras)
It is wheather sealed
Comes in black and silver, aluminium finish
Lens hood is integrated
Availability to be announced in 2021
05-29-2020, 03:36 AM   #561
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It's sure that is has between f2.8 and f4.0. According to DPreview it's 2.8.
Motor is DC type.
05-29-2020, 03:42 AM - 4 Likes   #562
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It is 21mm. It is Pentax made. It is made of metal and glass. F/x does not matter much :O

05-29-2020, 04:06 AM - 1 Like   #563
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QuoteOriginally posted by angerdan Quote
It's sure that is has between f2.8 and f4.0. According to DPreview it's 2.8.
Motor is DC type.
DPR probably copy-pasted the f/2.8 aperture of the 16-50 PLM they reported in the following sentence.

With that size it's gonna be faster than f/2.8. The D FA 21 will be roughly similar to the D FA 28-105 in size (73 x 86.5 mm);

FA 20/2.8 at a smaller size of 70 x 44 mm
FA* 24/2 at a smaller size of 72.5 x 65.5 mm

The Nikon 20/1.8G is slightly larger at 82.5 x 80.5 mm (with half the front of the barrel being clearance for a wide angle hood, the front element is ~49mm in diameter).
05-29-2020, 04:12 AM   #564
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QuoteOriginally posted by willdmo Quote
Okay people. you proved me wrong to some point, The Lines with for cant be used to judge how fast the lens can be, except for that it is faster than F4, otherwise the markings would need to start with a higher number like 5.6 (unlikely) or F8.
Given the looks, it is more a hefty of a lens than the other limited lenses and therfor can be faster, on the other hand the really fast lenses are more expected in the ★ lineup.

I think what we know for sure is:
The lens is faster than F4
And everything else was already in their press release:
It is a 21mm lens without aperture ring so basically useless on all film bodies without dial for apertures
The lens has no screwdrive AF (no AF at all on analog cameras)
It is wheather sealed
Comes in black and silver, aluminium finish
Lens hood is integrated
Availability to be announced in 2021
It's also KAF4, so only fully open aperture on anything before K-50/K-3...
05-29-2020, 09:21 AM   #565
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Its a lens of desire
Hopefully we can test it soon and the virus is not harming its release
05-29-2020, 09:33 AM   #566
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QuoteOriginally posted by phoebus Quote
It's also KAF4, so only fully open aperture on anything before K-50/K-3...
Do we know it is KAF4?

All the DA limiteds are KAF3, right?

-Eric
05-29-2020, 09:36 AM   #567
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QuoteOriginally posted by TwoUptons Quote
Do we know it is KAF4?

All the DA limiteds are KAF3, right?

-Eric
The DA 20-40 is KAF3, the other DA Ltds are KAF.
05-29-2020, 09:37 AM   #568
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QuoteOriginally posted by TwoUptons Quote
Do we know it is KAF4?

All the DA limiteds are KAF3, right?

-Eric
The models they show in the video don't have any visible aperture levers, but they might be mock-ups which... don't have aperture levers .
05-29-2020, 09:40 AM - 1 Like   #569
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Ah, man, I hope it is KAF 4. I understand that that limits sales to people with older cameras but the newer mount is just so nice. So are the K-3 and newer cameras. There are still plenty of lenses that fit the older mounts.
05-29-2020, 09:53 AM   #570
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QuoteOriginally posted by Zygonyx Quote
It will have to be f/2.
Again, the good comparison is with FA*24/2 and i don't see any interest if slower.
That would be true if it were a DFA* lens but does not apply to a DFA Limited. There are two distinct lens lines, Star lenses and Limited lenses, with distinct design briefs and output profiles. A 21mm Limited lens can be f/2.3 or f/2.4 and still meet the design brief. A Star lens would need a wider maximum aperture to meet the design brief.

IMO there will be a DFA* 24/2 or wider and this 21mm Limited will be (my guess) f/2.3.
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