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04-08-2021, 03:54 AM   #1246
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QuoteOriginally posted by repaap Quote
I would be quite surprised if edges would not be sharp by f4. It is 'star' lenses which has edges sharp from wide open or a bit stopped down. atleast these new DFA* has.

I dont think hat this new FDA limited will be that much of a compromise. Also 9 rounded blades should give nice smoothness(at close distances) even stopped down to f5.6. even if it is wide lens.


@ f 8 it should be edge to edge sharp and all good. My FA 31 is very sharp from 5.6 to 8 and up.
It's only recently that lenses around 20mm show great edge sharpness at f4. Lenses like the very good zeiss 21mm f2.8 do show noticeable degradation. I don't really know what to expect from a dslr ~20mm prime in 2021. The DA11-18 behaves like this at f4 according to the pf review.

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---------- Post added 04-08-21 at 04:05 AM ----------

Oh and just to add to Ooku's question. Considering the size and fov I'd say that f2.8 would be very good but then again Leica has a small 21mm f1.4 so why should Pentax be any worse


Last edited by house; 04-08-2021 at 04:08 AM.
04-08-2021, 04:36 AM   #1247
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QuoteOriginally posted by house Quote
It's only recently that lenses around 20mm show great edge sharpness at f4. Lenses like the very good zeiss 21mm f2.8 do show noticeable degradation. I don't really know what to expect from a dslr ~20mm prime in 2021. The DA11-18 behaves like this at f4 according to the pf review.

center

corner


---------- Post added 04-08-21 at 04:05 AM ----------

Oh and just to add to Ooku's question. Considering the size and fov I'd say that f2.8 would be very good but then again Leica has a small 21mm f1.4 so why should Pentax be any worse
DFA21 will be quite recent.

About leica 21/1,4. Why small? Made for rangefinder camera and it is actually apsh lens. Sure, for FF. And a bit expensive, and a bit of PF.
04-08-2021, 02:12 PM   #1248
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QuoteOriginally posted by Sandy Hancock Quote
It might be an expensive few months. I doubt I will able to show any patience when/if the DFA 21/2.x Limited and DA* 16-50/2.8 get a release soon....
Good thing you are a rich doctor. Imagine the level of pain us poor construction workers feel....
04-08-2021, 06:18 PM - 1 Like   #1249
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QuoteOriginally posted by OoKU Quote
With such a filter size and guaranteed optical quality, what aperture do you think is satisfactory?
Very simple :
1- it cannot be 2.8 whilst this would be redundant with the 15-30mm zoom and not "FA Limited compliant" (too slow)
2- it won't be 1.4 given the close construction and size caracteristics with lesser FOV to the FA* 24/2
3- we have seen that on the initial mock-up there was only space for one digit on the barrel's inscriptions (and Ricoh has since modified two times this detail on subsequent copies)

So f/2 seems evident.

04-08-2021, 06:21 PM - 2 Likes   #1250
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QuoteOriginally posted by Zygonyx Quote
Very simple :
1- it cannot be 2.8 whilst this would be redundant with the 15-30mm zoom and not "FA Limited compliant"
2- it won't be 1.4 given the close construction and size caracteristics with lesser FOV to the FA* 24/2
3- we have seen that on the initial mock-up there was only space for one digit on the barrel's inscriptions (and Ricoh has since modified two times this detail on subsequent copies)

So f/2 seems evident.
It could still be f/e
Almost 2.8, yet weird enough for a Limited...

e (mathematical constant) - Wikipedia)

But I am expecting between f2 and f2.8...

-Eric
04-08-2021, 06:22 PM - 3 Likes   #1251
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QuoteOriginally posted by TwoUptons Quote
It could still be f/e
Almost 2.8, yet weird enough for a Limited...

e (mathematical constant) - Wikipedia)

But I am expecting between f2 and f2.8...

-Eric
I have zero need for a D FA 21mm limited as an APS-C and 645 shooter. But as someone with a PhD in mathematics, I would have to buy the lens if it were f/e.
04-08-2021, 11:59 PM   #1252
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QuoteOriginally posted by Zygonyx Quote
So f/2 seems evident.
I hope they read that !

04-09-2021, 01:04 AM   #1253
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QuoteOriginally posted by mtkeller Quote
I have zero need for a D FA 21mm limited as an APS-C and 645 shooter. But as someone with a PhD in mathematics, I would have to buy the lens if it were f/e.
Haha! I do hope it's a bit larger than that, f/sqrt(5) would be fine!
04-09-2021, 01:26 AM - 5 Likes   #1254
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f/π would be a circular argument
f/e would be natural
f/phi would be gold

but f/i would be purely imaginary
04-09-2021, 01:36 AM   #1255
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QuoteOriginally posted by gazonk Quote
Haha! I do hope it's a bit larger than that, f/sqrt(5) would be fine!
I'd find it very appropriate if it were a 21mm f/2.1, but that might be a bit too large... like I told OokU f/sqrt(7) is still very much acceptable to me
04-09-2021, 02:31 AM   #1256
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QuoteOriginally posted by house Quote
It's only recently that lenses around 20mm show great edge sharpness at f4. Lenses like the very good zeiss 21mm f2.8 do show noticeable degradation. I don't really know what to expect from a dslr ~20mm prime in 2021. The DA11-18 behaves like this at f4 according to the pf review.

center

corner


---------- Post added 04-08-21 at 04:05 AM ----------

Oh and just to add to Ooku's question. Considering the size and fov I'd say that f2.8 would be very good but then again Leica has a small 21mm f1.4 so why should Pentax be any worse
I would think that by f4 it will be pretty good. Wide open, nearly all lenses (except big, highly engineered ones) have some softness on the borders. Pentax is trying to walk a fine line to keep the size under control, but to also have a lens that performs well with testing.

I doubt this will be a favorite for astro shooters. Probably better to go with a faster option with less coma.
04-09-2021, 02:33 AM - 1 Like   #1257
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Sony 20mm 1.8 has 67mm filter and weighs 373 grams. I feel that for the DFA 21, F2 should be achievable.
04-09-2021, 03:02 AM - 2 Likes   #1258
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QuoteOriginally posted by Sandy Hancock Quote
f/π would be a circular argument
f/e would be natural
f/phi would be gold

but f/i would be purely imaginary
Maybe that’s where the pixie dust is... in the imaginary part of the aperture...

-Eric
04-09-2021, 03:58 AM   #1259
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QuoteOriginally posted by BarneyL Quote
Sony 20mm 1.8 has 67mm filter and weighs 373 grams. I feel that for the DFA 21, F2 should be achievable.
But the Sony 20/1.8 looks like it's about 2cm longer than the Pentax DFA21 and this is with a short flange distance design. The front element looks larger as well. These things considered the DFA21 will have to be slower or perform very "differently"

MTF's can lie, and it's the wrong fl, but the new Samyang 24 does look very good as well and a bit closer in size. Perhaps UWA's are indeed improving as much as is said. Here's hoping that it's not the famous short flange advantage starting to show up. The price of that performance, if true, is shockingly low.

Samyang Optics

04-09-2021, 05:30 AM   #1260
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QuoteOriginally posted by BarneyL Quote
Sony 20mm 1.8 has 67mm filter and weighs 373 grams. I feel that for the DFA 21, F2 should be achievable.
Size is relative to flange distance versus focal length.

So unless you can present an autofocussing Sony 49mm F2 that is smaller than the small version of the DA 40 limited you compare apples to oranges.
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