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01-24-2011, 08:30 PM   #1
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random question about pentax da 12-24

hey all

just discovered two things about the pentax da12-24 (which ftr i quite like).

first off, the pentax website spiel says the following about it:


QuoteQuote:
The image circle in DA-series lenses is designed to perfectly match the 23.5mm x 15.7mm size of the CCD used in PENTAX digital SLRs to optimize camera performance.

second thing i found is very very heavy vignetting wide open at 12 - 13mm, and still slightly visible just above f4.

my questions is, why would they write something like "designed to perfectly match", when it vignettes so heavily? is that pushing it / a bit misleading to you? or is it rather just an inherent factor with the lens? (keeping in mind it's made for digital)

just wondered what others thought.

andrew.

01-24-2011, 10:11 PM   #2
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QuoteOriginally posted by imaspy Quote
hey all

just discovered two things about the pentax da12-24 (which ftr i quite like).

first off, the pentax website spiel says the following about it:





second thing i found is very very heavy vignetting wide open at 12 - 13mm, and still slightly visible just above f4.

my questions is, why would they write something like "designed to perfectly match", when it vignettes so heavily? is that pushing it / a bit misleading to you? or is it rather just an inherent factor with the lens? (keeping in mind it's made for digital)

just wondered what others thought.

andrew.
it is a nature of the lens, be it film or digital. to avoid or lessen vignetting, adjust your f-stops at smaller apertures.
01-24-2011, 10:41 PM   #3
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One of my most-used lenses, and I don't recall any noticeable vignette unless I had the lens hood rotated slightly :-)

12mm, f4.


12mm, f4.


What bothers me more is the occasional polarizer effect which makes the sky unnaturally dark.
[IMGtall]http://i133.photobucket.com/albums/q78/KylePix/Places%20Generally/N%20Cal-S%20Oregon%2010/D9%20-%20Coquille-Honeydew/100528-7357CoquilleRLighthouse.jpg[/IMGtall]
01-25-2011, 12:10 AM   #4
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QuoteQuote:
imaspy: my questions is, why would they write something like "designed to perfectly match", when it vignettes so heavily? is that pushing it / a bit misleading to you? or is it rather just an inherent factor with the lens? (keeping in mind it's made for digital)
The Da 12-24 f4 definitely has some heavy vignetting, wide open, @ 12mm--but then that is no secret and is expected for UWA. Since when has advertizing been realistic, or made to illuminate truth? No, the goal in advertisizing is to be as flowery as possible, generating sales first and foremost.

Are you really surprised?


Last edited by Jewelltrail; 01-25-2011 at 10:20 AM.
01-25-2011, 04:12 AM   #5
Ash
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I've personally noticed no vignetting with my copy, but then again I've found no WA situation where I needed to shoot at f/4. It's always been f/8 or smaller to maximise IQ and DoF. Reviews of the lens's performance at 12mm are actually very good - Photozone rates it excellent in resolving power straight from f/4, and vignetting is barely over a stop at f/4 and under half a stop at f/8 at 12mm:



There are a number of high end UWA lenses that exhibit the same issues.
01-25-2011, 04:20 AM   #6
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There is vignetting at 12mm WITH the lens hood on. Just take it off at 12mm or move up to 14mm.
01-25-2011, 05:14 AM   #7
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QuoteOriginally posted by kbryant Quote
There is vignetting at 12mm WITH the lens hood on. Just take it off at 12mm or move up to 14mm.
This is a good test. My 12-24mm hood requires reasonable force to click into place and the lens will vignette if it is not fully home.

dave
01-25-2011, 10:18 AM   #8
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QuoteQuote:
Ash: I've personally noticed no vignetting with my copy, but then again I've found no WA situation where I needed to shoot at f/4.
Yes, as the Phototozone chart clearly shows, the problem is only @ 12mm f4. I personally have found no reason to shoot my UWA wide open either.

01-26-2011, 03:54 AM   #9
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i'll post a couple of samples from when i've shot at f4 12mm with no hood.

as others have said, i dont disagree that f4 @ 12mm is not the most common way to shoot in the world; it's more about what pentax wronte.

anywho it's no biggie, as i said, just wondered what others had thought
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