I have a K1..

Started Aug 19, 2019 | Questions
TomWret
TomWret Veteran Member • Posts: 3,843
I have a K1..

What do you use to shoot at to tell if your Lens' are front focusing and what is the procedure to correct?

Thanks, Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

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Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
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DougOB
DougOB Senior Member • Posts: 1,851
Re: I have a K1..
1

TomWret wrote:

What do you use to shoot at to tell if your Lens' are front focusing and what is the procedure to correct?

Thanks, Tom W

There are a lot of test targets out there that you can get.  Some you can buy but I download a free one somewhere.  They are easy to find online.

Typically to shoot at a 45deg angle at the target at the centre point then examine the picture to see how much it is out.  Usually I start with three shots with the adjustment set at -5, 0, +5 and then iterate from there.  On a tripod, center focus point, shoot wide or close to wide open, ...

If they are all front focusing then it is possible you only need a single global adjustment for all your lenses as opposed to separate values for each lens.

Or send the K-1 in for adjustment

Doug

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PeterPentax
PeterPentax Contributing Member • Posts: 868
Re: I have a K1..

Chart here http://www.kscameraclub.org/docs/pdfs/focus_test_chart_edited.pdf

In addition to the advice given , try and use natural light.

Also do not rely on one test. You need to be making the camera focus from infinity and min focus distance each time. Do 10 of each. Go with the majority result. PDAF is just not accurate enough to rely on one test

DougOB
DougOB Senior Member • Posts: 1,851
nt +1

No text.

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John_A_G Veteran Member • Posts: 7,942
Re: I have a K1..

I always found using a stuffed animal was good.  I focus on the eye and take 3 shots, defocusing the lens in between.  Then I look for focus on the snout vs eyes vs ears.

I don't have a K1, so i don't know how many intervals are in the microfocus adjust, but on my cameras I would do large jumps and narrow it down (like eyeglasses) - So +5, +10, +15, +20.  download that sequence and review on large monitor.  Then when I narrow it down to say +10 and +15 I would try to find the best value between those two.

TomWret
OP TomWret Veteran Member • Posts: 3,843
Re: I have a K1..

Thanks Doug.

Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

 TomWret's gear list:TomWret's gear list
Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
TomWret
OP TomWret Veteran Member • Posts: 3,843
Re: I have a K1..

Good to know Peter.

Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

 TomWret's gear list:TomWret's gear list
Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
TomWret
OP TomWret Veteran Member • Posts: 3,843
Re: I have a K1..

Thanks John.

Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

 TomWret's gear list:TomWret's gear list
Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
Joseph Tainter Forum Pro • Posts: 11,383
Re: I have a K1..

The 45 degree test doesn't work for wide angle lenses.

I put a test target on a wall, then shoot varying the correction from +3 to -3, and further if needed. I look at the images onscreen, center and all corners and sides, and enlarged to 100%.

Joe

candgpics Regular Member • Posts: 167
Re: I have a K1..

Hi:

I use the chart B&H provides in the middle of the article here:

https://www.bhphotovideo.com/explora/photography/tips-and-solutions/how-to-test-your-lens

You can click on the link to the picture of the chart and print it.

I then shoot at the widest aperture or perhaps stopped down very slightly (e.g., test the 31 Limited at 1.8 or 2.0), using a tripod pointing downward towards the chart at about 45 degrees, at or near minimum focus distance.  It helps to do this under indoor and outdoor light since the focusing can vary a bit under different light sources.

Hope this helps!

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Terry K1
Terry K1 Senior Member • Posts: 1,360
Re: I have a K1..

I use a Vello focus adjustment chart mounted to a light stand. Just had to do an adjustment to my DFA 50 f/1.4. It was front focusing and took -7 to correct it. My FA 43 was back focusing, and took +10 to correct. I started with +7, and reshot it from +7 to +10. Both lenses are drastically improved now. Any help you get from PeterPentax, just do it. He was a tremendous help to me.

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DougOB
DougOB Senior Member • Posts: 1,851
Re: I have a K1..

PeterPentax wrote:

Chart here http://www.kscameraclub.org/docs/pdfs/focus_test_chart_edited.pdf

FWIW, this is the chart that I use.

In addition to the advice given , try and use natural light.

Also do not rely on one test. You need to be making the camera focus from infinity and min focus distance each time. Do 10 of each. Go with the majority result. PDAF is just not accurate enough to rely on one test

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ozdean
ozdean Forum Pro • Posts: 26,282
Re: I have a K1..

A ruler at 45 degrees

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Regards Dean - Capturing Creation
N.B. All my Images are Protected by Copyright

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phil_t Regular Member • Posts: 125
Re: I have a K1..

Here is a link to info needed to make the one that I use:

http://www.squit.co.uk/photo/files/FocusChart.pdf

I prefer this one because the target is large and perpendicular, so there’s no ambiguity about what you’re camera is actually focusing on.  Easy to fabricate with a small amount of foam core, sharp mat knife, spray adhesive and card stock for the ink jet.

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M R Padmaraju Veteran Member • Posts: 5,101
Re: I have a K1..

Congrats .

Regards ,

mrp .

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Sweets
Sweets Contributing Member • Posts: 710
Re: I have a K1..

How real/possible is it that Pentax creates an automated system to do the focus-adjustment-settings per lens? Something like calibrating the lens on the camera… ?

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rgrds. Henk (K-1+DBG6 & -01, GF2+14042X & LBA).

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TomWret
OP TomWret Veteran Member • Posts: 3,843
Re: I have a K1..

Thanks to all who have given me suggestions.

Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

 TomWret's gear list:TomWret's gear list
Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
Terry K1
Terry K1 Senior Member • Posts: 1,360
Re: I have a K1..

Tom, what lens are you adjusting?

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TomWret
OP TomWret Veteran Member • Posts: 3,843
Re: I have a K1..

Terry the Pentax 100mm 2.8 macro.

Tom W

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...a bad picture is like a missed putt, it's never your fault: My new site fineartamerica.com/profiles/3-thomas-whitehurst

 TomWret's gear list:TomWret's gear list
Pentax K-1 Pentax smc DA* 50-135mm F2.8 ED (IF) SDM Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited Pentax smc D-FA 100mm F2.8 Macro WR +9 more
Terry K1
Terry K1 Senior Member • Posts: 1,360
Re: I have a K1..

I use 25 x the focal length for the distance from my target.

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