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11-15-2021, 08:13 AM   #31
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QuoteOriginally posted by c.a.m Quote
Interesting. Do I understand correctly that the focus was accurate only at the single center point, and not at any of the adjacent points?

Thanks.

- Craig
Center point, focus every time.

Row below center, all of them front focus, more or less. Maybe 5% in focus. The worst points the closest below center.

Same row as center, some in focus.

Row above center, some in focus.

Very different subjects.

I tested at 50 mm and a little at 16 mm but since most gave me trouble I gave up.

11-15-2021, 09:11 AM   #32
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The skill here is in using a ƒ/stop with enough DoF, to cover the inconsistency of AF. I have many times used the edge AF points successfully. It's only in photography that needs precision that AF inconsistency is a problem. And for that, Live View is your friend, in that allows you to precisely position the focal plane.
11-15-2021, 09:46 AM - 1 Like   #33
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QuoteOriginally posted by normhead Quote
The skill here is in using a ƒ/stop with enough DoF, to cover the inconsistency of AF. I have many times used the edge AF points successfully. It's only in photography that needs precision that AF inconsistency is a problem. And for that, Live View is your friend, in that allows you to precisely position the focal plane.
If you buy a 2.8-lens you should be able to use the lens at 2.8. Especially with the focus points closest to center because there there is no difference in DOF. Also this lens is so sharp at the edges fully open that at the farthest focus point it should not be a problem anyway.

I have long and deep experience on matters like this.

I tested both far away and closer and the problem persisted. With my DFA24-70 there was no problem at all.

And, the focus is not inconsistent, it hits the same place all the time, the problem is that center point hits where you want it and the rest front focuses approx 5-7 points.

Last edited by Tjompen1968; 11-15-2021 at 09:53 AM.
11-15-2021, 10:31 AM   #34
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QuoteOriginally posted by Tjompen1968 Quote
I tested both far away and closer and the problem persisted. With my DFA24-70 there was no problem at all.
Thanks for your comments.

I guess the question is: Why would one lens at 50mm (16-50 PLM) exhibit mis-focus issues while the other lens (DFA 24-70) operate perfectly at the same focal length? I know the optical designs are different. I am surprised that the 16-50 misfocuses even when using AF points very close to the centre one.


I don't have either lens but I do own a K-3 Mark III. I pay attention to reports like this one, in case I notice any issues with my own lenses.

- Craig

11-15-2021, 11:19 AM   #35
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That can and sometimes happens, I've had 2 DA*16-50 of wchich first was fine as is and the second was backfocusing.
You adjust for the lens and it should focus fine.
But a lens that focuses correctly on some points and needs adjusting on others is something new to me.
You can't adjust it normally because when you correct for one points it messes with the others(wchich happened in my case).

QuoteOriginally posted by c.a.m Quote
Thanks for your comments.

I guess the question is: Why would one lens at 50mm (16-50 PLM) exhibit mis-focus issues while the other lens (DFA 24-70) operate perfectly at the same focal length? I know the optical designs are different. I am surprised that the 16-50 misfocuses even when using AF points very close to the centre one.


I don't have either lens but I do own a K-3 Mark III. I pay attention to reports like this one, in case I notice any issues with my own lenses.

- Craig

Last edited by Settesz; 11-15-2021 at 11:30 AM.
11-15-2021, 01:10 PM   #36
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Did I say that it behaved the same on my K-1? Well, it did.
11-16-2021, 07:00 AM   #37
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QuoteOriginally posted by licht96 Quote
Hello.
My Camara is now since more than two weeks in maintenance (not the best and fastest here in Germany).
Because - different to you, guys - I've the same problem with other lenses (35 2.0 (screwdrive) and the 55 1.4 (SDM)).
I explored and first faced the problem with the 16-50 PLM, too.

Honestly speaking : when it (the camera) comes back with the result, that everything is in specification limits... Than I really think about leaving the system.

I really was looking forward to use the outer focus points do get a little bit rid of the old recompose half pressed AF...
I've had so many Pentax cameras... And own so much lenses... Still being proud to use our brand... But when this is true, I am really at the end.

When this is not usable with the newest camera and the newest lens... What did I pay for? What are all the AF points for?

And again: I tried this with the most contrast things I can imagine : this QR code pattern in the middle of the focus sheet: black white, black white, black white... In every direction.

@Settesz : when you first wrote you are happy with correction in AF, because it solves the problem in this critical edges, without making problems in the center... I couldn't believe it...and now it seems, you see there IS a problem doing this in that manner.
I have conducted a few extensive portrait shoots with my K-3iii and and HD PENTAX-DA 16-85mm F3.5-5.6 ED DC WR Lens (my everyday lens), with no problems using various focus points. After your post, I have purposely shot images with the full spectrum of focus point locations with no problems. I have repeated this with my DA 35mm F2.4 AL Lens at f2.8, again with no problem. Hence it sounds like the camera communication with your 16-50 PLM lens is slightly off. The latest camera firmware version is 1.20 - loading this may cure the problem.

11-16-2021, 07:26 AM - 1 Like   #38
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It didn't work out after all.:P
While the lens did start to focus correctly it seems it works from focal around 25mm and up.
On wide end only the central points are accurate.
I checked it on KP and it's more or less the same. Also checked k3iii with other lenses(older DA*16-50 among them) and it focuses without any problems with all points on all focal lenghts.
So I'm sending it to repair service after all.:P
11-16-2021, 07:30 AM   #39
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QuoteOriginally posted by Settesz Quote
It didn't work out after all.:P
While the lens did start to focus correctly it seems it works from focal around 25mm and up.
On wide end only the central points are accurate.
I checked it on KP and it's more or less the same. Also checked k3iii with other lenses(older DA*16-50 among them) and it focuses without any problems with all points on all focal lenghts.
So I'm sending it to repair service after all.:P
Sorry to hear that. If I had to hazard a guess, it sounds like the lens firmware needs tweaking... but that's just speculation. Please keep us posted on the outcome?
11-16-2021, 07:45 AM   #40
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Will do!

QuoteOriginally posted by BigMackCam Quote
Sorry to hear that. If I had to hazard a guess, it sounds like the lens firmware needs tweaking... but that's just speculation. Please keep us posted on the outcome?
11-17-2021, 07:08 AM   #41
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QuoteOriginally posted by BigMackCam Quote
Sorry to hear that. If I had to hazard a guess, it sounds like the lens firmware needs tweaking... but that's just speculation. Please keep us posted on the outcome?
Hope it gets fixed. I talked to the service center in Sweden and he said there was no settings in the firmware for the lens that addresses individual focus points. Just the different kinds, i.e 2.8 and 5.6, cross type etc.
11-26-2021, 09:06 AM   #42
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So a quick update-I was refunded by the store, didn't get any info from repair service unfortunatly.


QuoteOriginally posted by BigMackCam Quote
Sorry to hear that. If I had to hazard a guess, it sounds like the lens firmware needs tweaking... but that's just speculation. Please keep us posted on the outcome?
11-26-2021, 09:52 AM   #43
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QuoteOriginally posted by Settesz Quote
So a quick update-I was refunded by the store, didn't get any info from repair service unfortunatly.
Glad to hear the matter's resolved, financially at least...
12-08-2021, 11:41 AM - 1 Like   #44
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So after all I got some time to make a focus test.
For the history: after 4 weeks my camera returned from the repair store. Only one comment on the sheet: calibrated.


After some shots with my daughter using Auto or a dedicated AF point: no change….a lot of pictures where out of focus.


The subject recognition worked quite well….but only in the viewfinder…often I was happy to see here, that it choosed an eye or even both…sometimes “only” the face with 5,3,4,5 points….but non of them where in focus, although the LCD panel with red dots and zoomed picture in the focus area showed the correct area with lots of contrast and subjects with “lines” in vertical and horizontal direction.
So I took an hour of time (in very hard to find actual ;-) ), with a lot of light (no daylight since it´s winter in Germany and I´ve to work…but I think the mix out of below mentioned sources must be ok)…
…and a focus test with – in my understanding – enough contrast/objects to work properly.
I know: this is not an laboratory test and there are still some variables I forget. So for all the “you forget something, so It can´t work!” => this was only a proof for me that it is not what I would expect from a AF Sytemen like that…that it is not the shaking of my hand, the wrong exposure time, the wrong expectation when I “only” took a circular eye (close up shot) or a head (distance shot).
I was a little bit angry afterwards that,although I align the camera and the focus screen in the best way => I had to rotate the image 1.05° to show them not exactly vertical…but as I say=> no laboratory (and not 4 hours of time)
Results shown below. A little bit the pity is, that the FrontFocus/BackFocusPattern don´t really show a “strategy” of a misalignment….



Firmware 1.21
Lens HD Pentax DA* 1:2.8 16-50mm EDPLM AW
Focal length 50mm
Aperture 2.8
ISO 200
Exposer Time 1/320
Exposer Comp -0.7
SR Off
White Balance 5000 K
Focus Adjustment to center +2
Lights: 2 incandescent lamp
1LED floodlight
1Phillips day time lamp
21°C
Distance Focal plane camera toFocus Test target 1,3 m (LCD AF Frame is more or less so big as small B/WTarget near measurement ruler)
Camera horizontal and verticaladjusted with internal balance
Target with bubble balance –although the picture is shifted 1.05° to the right
Before each shot the lens wasdefocused
Attached Images
                 
12-08-2021, 12:14 PM   #45
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QuoteOriginally posted by licht96 Quote
So after all I got some time to make a focus test.

...
...
Thanks so much for posting your results... This kind of feedback is really valuable to the community.

That is, frankly, bizarre behaviour (the lens, I mean - not you ).

The only thing I can really call into question - and I mention this constructively; not as criticism of your otherwise thorough approach - is the mix of lighting sources, and whether any of them are confusing the PDAF sensor. It would have been ideal to use daylight, but I appreciate that wasn't practical. The next choice - if I had been conducting the tests myself - would be a single light source known to work when shooting with other lenses, pointed towards the target at an angle (to avoid glare). In my own AF testing and AF fine adjustment sessions, I use a high quality, colour-temperature-controlled LED video light that I've previously tested extensively to confirm it has no effect on AF whether it's the only light source or mixed with daylight...
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