K20D and P(MTF)


gartmore

Link Posted 03/06/2010 - 08:51
I've been using P(MTF) quite a bit and particularly for street photography believing that at this setting my lenses would perform at their best. In some instances the results have been quite surprising with apertures being much wider than I would have suspected. On an average sunny day with the same subject matter here are my findings of what the camera selects:

DA 18-55 @ 18mm = f4.5
DA 18-55 @ 55mm = f6.7

DA 16-45 @ 16mm = f4
DA 16-45 @ 45mm = f5.6

DA 50-200 @ 50mm = f4.5
DA 50-200 @ 200mm = f6.7

DA 40 LTD = f4

I must say I'm very surprised at the 'wide open' results
Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

MarkD

Link Posted 03/06/2010 - 09:01
But how did the pictures look?
.........all the gear, no idea!
Me super, MX, LX, K5,DA 18-55WR, DA 17-70, DA 55-300, DA40 Ltd, FA50 1.4, Samsung D-Xenon 12-24,Samsung 100mm macro M50 1.7(x3), M28 3.5, M35 2.8, M100macro f4, M135 3.5(+others)

simonkit

Link Posted 03/06/2010 - 11:13
I must admit to being quite sceptical regarding the usefulness of MTF, consequently I've never used it. It's interesting to hear how your shots have turned out using the setting though

Simon
My website http://www.landscapephotographyuk.com

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gartmore

Link Posted 03/06/2010 - 12:54
The pictures are fine of course, I'm just surprised at the results since received wisdom and anecdotal evidence suggest these lenses perfom best stopped down a bit more. Pentax clearly think differently.
Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -
Last Edited by gartmore on 03/06/2010 - 12:55

johnriley

Link Posted 03/06/2010 - 13:03
It is true that theory says that best resulots will be had at wider apertures, but that depends on a more or less perfect lens design.

Most zooms performa better stopped down more. I wonder if they have assumed no decentering for the MTF values - in other words, the theoretical best performance assuming a perfectly assembled lens.
Best regards, John

gartmore

Link Posted 03/06/2010 - 13:19
I think you might be right John, primes are so good that perhaps it doesn't matter much which f-stop you use but with zooms it must be based on theoretical lenses.

Interestingly, though, my 18-55 at f6.7 is stunningly sharp but I still would have thought that the zoom figures might have been the other way round.
Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

MarkD

Link Posted 03/06/2010 - 15:08
It may be that the selection is a compromise between sharpness and bokeh(...or depth of field).
Although I have to say I have been quite suprised how sharp many of my lenses (older primes and DA kit zoom) can be at maximum aperature under the right lighting conditions.
.........all the gear, no idea!
Me super, MX, LX, K5,DA 18-55WR, DA 17-70, DA 55-300, DA40 Ltd, FA50 1.4, Samsung D-Xenon 12-24,Samsung 100mm macro M50 1.7(x3), M28 3.5, M35 2.8, M100macro f4, M135 3.5(+others)
Last Edited by MarkD on 03/06/2010 - 15:14

kerrowdown

Link Posted 05/06/2010 - 23:47
I'm still using F8 and be there.
My Harem of Ladies.... “Mistress" (Pentax-A 15mm F3.5 ), "Good Lady” (Pentax-A 20mm F2.8 ), “Friendly Lady” (Pentax-A 24mm F2.8 ), "Deviate Lady" (Pentax 28mm F3.5 Shift ), "Street Lady" (Pentax-A 28mm F2.8 ), "Retro Lady" (SMC Pentax-M 40mm F2.8 ), "Special Lady” (Pentax-A 50mm F1.2 ), “Femme Fatale” (Pentax-A 50mm F2.8 Macro ), “Sweetheart” (Pentax-A* 85mm F1.4 ), "Lady Luck” (Pentax-A* 135mm F1.8 ), “Gorgeous Lady” (Pentax-A* 200mm F2.8 ED ), “Duchess” (Pentax-A* 300mm F4.0 ) and "HM The Queen" (SMC Pentax 500mm F4.5 ).
Last Edited by kerrowdown on 05/06/2010 - 23:48
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