K1 & FA 50mm f1.4 lens fine focus calibration issue


johnducguz

Link Posted 25/04/2021 - 13:26
So I've adjusted the FF on the K1 for my lenses but the 50mm gives me issues.
I've a sheet of paper angled at 45 degrees away from me with horizontal lines on it. 2 sec self timer set, set to f1.4, focus on the middle line & take a shot. Zoom in on shot image & it shows front focus. Don't alter anything but place hand in front of the lens to force focus to change, remove hand, focus on the middle line again & take a shot. Zoom in & now the line's in focus. Repeat & this time there's front focus again. Repeat & middle line's in focus.
So the camera isn't finding the same focus point each time meaning any fine focus adjustment isn't final.
I've made adjustments 3 times previously & still been left wondering why some shots aren't sharp. If the combo finds a different focus plane each time any adjustment isn't likely to work.
Anyone any idea what's going on? Why's this particular camera/lens combination giving differing focus results.
I'm baffled as my other lenses once adjusted have remained ok.

pschlute

Link Posted 25/04/2021 - 14:59
johnducguz wrote:

So the camera isn't finding the same focus point each time meaning any fine focus adjustment isn't final.

That happens with PDAF, although a 50% miss ratio is very poor. 10% is quite normal

johnducguz wrote:

Why's this particular camera/lens combination giving differing focus results.

I would give the AF sensor a blow with a rocket blower in case you have dust on it, but its a long shot.

Do you notice how the accuracy compares when you get the lens to focus from infinity versus from closest focus distance ?
Peter



My Flickr page

johnducguz

Link Posted 25/04/2021 - 15:45
Must admit I hadn't tried it at the extremes, I'll give it a go.
A quick blow around with the rocket can't hurt either.
Thanks for the input

pschlute

Link Posted 25/04/2021 - 16:11
johnducguz wrote:
Must admit I hadn't tried it at the extremes, I'll give it a go.
A quick blow around with the rocket can't hurt either.
Thanks for the input

Mirror up and the AF sensor is in the bottom of the mirror box

Do 10 tests from each extreme to get an accurate assessment.
Peter



My Flickr page
Last Edited by pschlute on 25/04/2021 - 16:13

FrankV

Link Posted 02/06/2021 - 15:35
I just recently bought a K1, to say itís a disappointment is an understatementi.
It doesnít focus properly.

Chrism8

Link Posted 02/06/2021 - 15:45
The K1 is a superb camera, there's obviously something wrong somewhere, care to elaborate on " it doesn't focus properly " what lens are your using, settings etc ?
Chris

www.chrismillsphotography.co.uk

" A Hangover is something that occupies the Head you neglected to use the night before".

-------------------------------------------------------------
K1 - Sigma 85mm F1.4, Pentax DFA 150 -450 F4.5 / 5.6, Pentax DFA* 24 - 70 F2.8

Sigma 100-300 F4, Samyang 14mm F2.8, Pentax DFA* 70-200 F2.8

K3iii + K3ii + K5iis converted to IR, Sigma 17 - 70 F2.8, Pentax 55 - 300 F4.5 / F5.6 PLM

pschlute

Link Posted 02/06/2021 - 15:54
FrankV wrote:
I just recently bought a K1, to say itís a disappointment is an understatementi.
It doesnít focus properly.

The k1 focusses perfectly, you are doing something wrong.
Peter



My Flickr page

Mike-P

Link Posted 02/06/2021 - 17:25
pschlute wrote:
FrankV wrote:
I just recently bought a K1, to say itís a disappointment is an understatementi.
It doesnít focus properly.

The k1 focusses perfectly, you are doing something wrong.

Wow, that's a bold statement, although unlikely it may just be a duff camera.
. My Flickr

pschlute

Link Posted 02/06/2021 - 18:02
Mike-P wrote:
pschlute wrote:
Quote:
I just recently bought a K1, to say itís a disappointment is an understatementi.
It doesnít focus properly.

The k1 focusses perfectly, you are doing something wrong.

Wow, that's a bold statement, although unlikely it may just be a duff camera.

Indeed it may be. But without any information from the poster about what his settings are, and some images to diagnose, I have no idea.

The K-1 has been in production for 5 years now. If it had a general focussing issue I think it would be apparent by now.

The most common mistake is someone moves from an older camera to a 36MP sensor unit like the K1. They then look at the images at 100% and see that focus is off without realising it was just as inaccurate on their older camera.

There is a reason all manufacturers have AF adjustment menu items.
Peter



My Flickr page
Last Edited by pschlute on 02/06/2021 - 18:06

Mike-P

Link Posted 02/06/2021 - 18:59
pschlute wrote:
Mike-P wrote:
Quote:
FrankV wrote:
I just recently bought a K1, to say itís a disappointment is an understatementi.
It doesnít focus properly.

The k1 focusses perfectly, you are doing something wrong.

Wow, that's a bold statement, although unlikely it may just be a duff camera.

Indeed it may be. But without any information from the poster about what his settings are, and some images to diagnose, I have no idea.




Exactly, so before declaring him incompetent perhaps it would be better to find out those settings because if you look back at his previous post he has been a long time user who is probably fairly well clued up on how to use a Pentax body
. My Flickr

pschlute

Link Posted 02/06/2021 - 19:11
Mike-P wrote:


so before declaring him incompetent perhaps it would be better to find out those settings

I am so used to folk moaning on forums of all types these days that I give these kind of posts short shrift.

If he wants help i have lots of experience fine tuning lenses with the K-1, and have offered that help on many occasions.

If he wants to just gripe I have no time.
Peter



My Flickr page
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