Sweet spot ?

Hi folks, does anyone out there know what aperture the da*55mm f1.4 is sharpest at. ?
Any help would be great.

Derek.

I would take an educated guess at f/4.0

thanks smeggypants. It would kind of defeat the purpose if you had to go out to f4 to reach peak sharpness ???:

Review here with mtf figures: link

Close! f3.5 and f4.5 with a slight dip at f4 !

John K

F/4.0 here. but I guess it's splitting pixels

http://www.photozone.de/pentax/471-pentax_55_14?start=1

how do you mean?




.

Does it really matter? I would guess it's pretty sharp at most apertures and I doubt that images would look soft even at F1.4.

Regards
David

I wonder what you expected. Don't forget there are FA and F versions of the 50mm f1.4 and the performance isn't massively worse to the DA* 55mm, but the SDM focussing of the DA* 55mm is reported as being slower than the 50mm screw drive of the 50mm's.

John K

David's right. Use it at the aperture you actually need. It's a DA* prime - it will be sharp enough!

thanks for all the responses, i suppose i meant that if you had to go out to f4 then there wouldnt have been much point in getting an f1.4. if you know what i mean. i think i probably need to fine tune the focus. at times it seems a little hit and miss as to where focus actually is.
i wll post some unedited images as soon as i get a chance.
Again thanks for the replies.

Derek

See you've got one! The DP review I linked to suggests it might need the focussing fine tuning. There one apparently needed -3 to overcome front focussing.

Look forward to seeing some images from it.

John K

There's more to life than sharpness

I use wide apertures for shallow Depth of Field, and very occasionally to get enough light for a fast enough shutter speed with a decent ISO. I never even think about sharpness when taking photos. You can easily sharpen a photo in processing if it's not crisp enough anyway



You should definitely check the AF calibration of all your lenses. Especially if you're shooting at narrow DOFs like 1.4

thanks again folks, will take a couple of shots in the morning (of clothes pegs) and post the results. one thing i havent tried is the lens without a filter, ive noticed some ghosting, depending on light and angles. that may also be an issue.
its good to know where the sweet spot is, on my da*300mm f4 it seems to be at f5.6, so i was surprised to learn that on the da*55 it was f4.
maybe its just me but it seemed like a lot of stops lost.
But i will test it in the morning with and without the filter.
thanks again

Derek

Derek, in theory most lenses perform best two stops from maximum aperture. So with an f/1.4 lens you might expect f/2.8, however, in practice lenses aren't perfect so that can vary. Many lenses peak at f/8 to f/11.

honestly folks, i appreciate all the input.
ive only recently taken up photography again after a couple of years off and having previously been a nikonian. though not to the extent that i am now a pentaxian
(Btw i think this is a super forum with an awesome wealth of knowledge and experience on here)

Derek