Focusing issues on Pentax cameras


Yecora99

Link Posted 24/07/2017 - 23:24
Hello,

Has anyone had any focusing issues on Pentax cameras?

I have had a Pentax K5 for some time now and have found my sharpness hit rate has dropped, even when using a tripod.

So I bought one of these Camera/lens calibrator card kits, which sit on top of a table at an angle with a flat plane of focus and a ruler and square marks along both outside edges to test the camera.

I set the camera on a tripod and tried different lenses through the aperture range and even though the auto-focus system said the focus point was on a barcode printed on the flat focal section of the card at the 0 mark the actual point of sharp focus was 1cm behind where the auto-focus system had said the focus point was.

Has anyone else had similar issues or is it just my camera?

I also own an Olympus OM-D EM-5 DSLR and the focus point on that is spot on.

Any suggestions as to what might be the cause and is there anyway I can adjust the focal point? note I have tried various lenses and they are all doing the same thing. The only time the 0 mark is sharp is when i stop the lens down to f16.
Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

JAK

Link Posted 24/07/2017 - 23:49
Just set the AF Fine Adjustment for either all the lenses or individually in Custom Menu 26. See page 126 of the K-5 manual if you're not sure. Normally its best to go for individual lenses as some will require a positive adjustment and some negative.

Re your comparison, the Oly EM-5 only has a contrast detect AF system so doesn't need an AF adjustment method whereas the K-5 has phase detection AF for TTL. If you want contrast AF on the K-5 use liveview making it like using the Oly. You have to set the AF method in the menu system (see page 166 in the manual.)

Contrast AF won't work in TTL as the mirror has to be up for the sensor to see the image!
John K
Last Edited by JAK on 25/07/2017 - 00:04

Jonathan-Mac

Link Posted 25/07/2017 - 07:39
As stated by JAK, you need to fine-tune the AF. This kind of problem is very common on DSLRs, not just Pentax.

It's a pain in the backside to do but once it's done then it should end your AF woes.
Pentax hybrid user - Digital K3 & K200D, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X digital
Fan of DA limited and old manual lenses

pschlute

Link Posted 25/07/2017 - 09:37
Agree with john and Jon..... get the AF tuned and you will notice a difference.

Larger and larger sensors means we can see the limitations of AF systems on cameras more easily.

When you do your AF tests.....

Tripod/test chart/natural light if possible. Use the widest aperture only to do the tests. Do many tests for each lens, getting the AF system to focus from infinity or nearest setting each time.
Peter



My Flickr page

stub

Link Posted 25/07/2017 - 15:15
Interesting....Never checked any of my lenses...
K1 K-5ii K7 Various lenses

Stuart..

pschlute

Link Posted 25/07/2017 - 16:03
stub wrote:
Interesting....Never checked any of my lenses...

I had slight backfocus issues with my lenses on my K10 , but there was no official AF fine tune adjustment so I lived with it as it was minor.

The K1 is different. 100% view on a 36mp vs 10 mp is in a different league. The slightest difference is like night and day. The sensors of today are actually showing up how big the manufacturing tolerances are when it comes to sensor positioning/AF sensor positioning.

Either you are lucky that your lenses/camera are in perfect alignment, or (this is a joke)...you should have gone to specsavers !
Peter



My Flickr page

wvbarnes

Link Posted 25/07/2017 - 18:26
No issues with any of my lenses over the years. I test lenses when i buy them and would return them if not focusing correctly. Mind you I've not owned faster than F2.8 where it becomes more critical i guess.
Bill

Yecora99

Link Posted 25/07/2017 - 21:08
Thanks for advising about the fine tuning option. I didn't have a user manual so was unaware about that option. I have now downloaded a PDF user manual and will follow the instructions and hopefully get my lenses to focus correctly.

I noticed the most recent images of wildlife was not always sharp on the eyes even though i focused on the eye (as you should) but found the other side of animals heads were in focus and not the eye closest to the camera and wondered what was the cause... now i know!
Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

jeallen01

Link Posted 25/07/2017 - 22:03
The tests I did a couple of years ago with the K-3/K-5/K-30 showed that several Sigma lenses had back/front focus issues with some of them - and that, in the end, that the K-3 was itself not correctly calibrated and had to be serviced by Johnsons (but that's another rather less-than-satisfactory story!).
K-3 II, K-3, K-5 & K-30, & some Sigma and Pentax lenses (and a lot of old 35mm gear!)
Last Edited by jeallen01 on 25/07/2017 - 22:04

Yecora99

Link Posted 25/07/2017 - 22:37
Well I have tried it and it does what it says in the manual, thanks to those who advised me about the AF fine tune calibration. I had to alter the focusing to the upper value limit of +10 see images below, both of these were taken with my f2.8mm Macro lens.





Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

jeallen01

Link Posted 25/07/2017 - 22:53
FWIW, you don't need to buy any special kit to do the adjustment - just get a 1m aluminium rule from your local DIY place, put a piece of masking tape on it to indicate the 50cm point, and set it at around 45 degs to the vertical at a suitable distance (will depend on the lens in question - I used a 10-15m distance for my long lenses) from the camera/lens.

Focus manually on the 50cm mark using Live View, and then use the AF mode when you press the shutter button (or, better, use an IR remote) - if the AF adjustment is correct, the resulting image will show the same focus point to be sharp. Otherwise the camera will have focused the lens in front of , or behind, the 50cm mark and then you know how to dial in the adjustment.

OTOH, if you get several lenses which all want the same nearly +/- 10 adjustments then suspect that the camera body itself needs recalibration.

Simples, when you get used to it (and I must do that with the 17-70 Sigma I just got from another forum member!).
K-3 II, K-3, K-5 & K-30, & some Sigma and Pentax lenses (and a lot of old 35mm gear!)

JAK

Link Posted 25/07/2017 - 23:10
Yecora99 wrote:
Well I have tried it and it does what it says in the manual, thanks to those who advised me about the AF fine tune calibration.

Pleased you have it resolved now.
John K

michaelblue

Link Posted 26/07/2017 - 00:01
If it's front focusing do you dial in plus or minus?
Regards,
Michael
My new website:link

richandfleur

Link Posted 26/07/2017 - 00:26
jeallen01 wrote:
FWIW, you don't need to buy any special kit to do the adjustment - just get a 1m aluminium rule from your local DIY place, put a piece of masking tape on it to indicate the 50cm point, and set it at around 45 degs to the vertical at a suitable distance (will depend on the lens in question - I used a 10-15m distance for my long lenses) from the camera/lens.

Good idea.

What's the vibe on distance to the subject? Do the results work better if it's up close than further away etc?

And What's the consensus around zoom lenses? If you have a 55-300, where does one look across the focal range to undertake this test?

pschlute

Link Posted 26/07/2017 - 05:46
michaelblue wrote:
If it's front focusing do you dial in plus or minus?

Front focussing...... use minus adjustment
Peter



My Flickr page
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