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02-16-2014, 02:22 AM   #1
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How do you 'calibrate the lens'?

In several threads in this forum I've been reading about people who say they have been 'calibrating the lens' by some function in the camera.

May I ask how this is done?

I bought a kit consisting of K-3 and the DA 18-135mm WR - and I don't think the photos are that sharp.

Could a lens calibration do the trick - and as mentioned: how do you perform this?

I know lack of sharpness can be helped by using a tripod - but nevertheless I'd like to be sure my lens is calibrated correctly.

Thank you kindly.


Last edited by Ztrejfer; 02-16-2014 at 02:43 AM.
02-16-2014, 02:34 AM   #2
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Calibration invokes a tripod or camera fixed to something. A cable release also helps but the 2 sec timer will do. A focus target is very handy and can be had from most good camera stores. In lieu of that an inclined tape measure with a target beside at a known point might work. You will find the adjust menu in C 4 number 26. I have calibrated all our lenses, but haven't really pushed them for sharpness due to current time restraints and very windy weather.

The kit lens might not be as sharp as say a Limited prime, but money does buy sharpness sometimes. Also don't ever forget the person behind d the camera, that is where my kit fails the most.

Hope this helps.
02-16-2014, 02:47 AM   #3
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Very helpful, thank you! :-)

This focus target you speak of - could it not be downloaded and printed out? And if so, where can a correct focus target be found on the internet?
02-16-2014, 02:52 AM   #4
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QuoteOriginally posted by Ztrejfer Quote
Very helpful, thank you! :-)

This focus target you speak of - could it not be downloaded and printed out? And if so, where can a correct focus target be found on the internet?
Google is your friend there. I just bought a focus target setup, but printing one would work as long as the print out was sharp enough, no fuzzy ink jet edges.

02-16-2014, 02:54 AM   #5
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02-16-2014, 03:12 AM   #6
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QuoteOriginally posted by Adam Quote
Thank you, AussieTrev and Adam - I'll follow your advices! :-)
02-16-2014, 06:26 AM   #7
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Ahemm - at least minus 10 just to calibrate a DA 18-135 WR with apparantly servere back-focus - on a K-3? That can't be right!

Last edited by Ztrejfer; 02-16-2014 at 06:35 AM.
02-16-2014, 09:31 AM   #8
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QuoteOriginally posted by Ztrejfer Quote
Ahemm - at least minus 10 just to calibrate a DA 18-135 WR with apparantly servere back-focus - on a K-3? That can't be right!
All that the 'calibration' does is to tweak an internal numerical offset in the camera software so that the contrast detect (live view/sensor) and the phase detect (viewfinder/PD module) focusing match.

First of all make sure that your camera and lens can focus well using live view. If not then there is something up with either the lens, the camera or your technique.

Rather than use one of the 'targets', which are usually too small to be of much use unless you have them far too close to the camera, try a distant contrasty object, a far away tree or a building. Misfocus at infinity will annoy you most. Then just take a series of shots with the camera on a tripod and a 2s delay, using the centre focus point and the lens wide open, stepping the offset between each and also remembering to defocus the lens between each shot. Pixel peep the centre, pick the sharpest shot offset. Unless there is something drastically wrong with your camera and/or lens the best offset will be somewhere between +2 and -2 in most cases. With a zoom lens it will probably also vary a bit with the focal length used and the focus distance. So don't get too obsessed with getting it right - in practice it is a compromise setting.


Last edited by kh1234567890; 02-16-2014 at 09:36 AM.
02-16-2014, 11:13 AM   #9
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QuoteOriginally posted by Ztrejfer Quote
This focus target you speak of...
I use a gray cement sidewalk the has one crack with some short grass. Really any uniform surface with one item as the focus point will work. You want to shoot at the largest aperture, such as f1.8.
02-16-2014, 02:53 PM   #10
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QuoteOriginally posted by SpecialK Quote
I use a gray cement sidewalk the has one crack with some short grass. Really any uniform surface with one item as the focus point will work. You want to shoot at the largest aperture, such as f1.8.
I too use a textured sidewalk with any small stone and/or twig that seems appropriate to the task. The textured surface in good light is excellent for determining the exact range of focus around the object.

I also use a Bus Ticket which has a dark magnetic strip on a white background for a target and a one meter steel rule (or a white tape measure) to determine the range of focus if the light is not great.
02-16-2014, 02:59 PM   #11
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Here is the cheap indoor method I use where I can create consistent lighting conditions. I've found reading the instructions takes longer than printing the targets and calibrating my camera for specific lenses.
PENTAX DSLRs: Front or Back Focusing Problems? Free test (Lens Alignment) charts for Pentax, Nikon, Canon, Sony, Olympus.
02-16-2014, 10:44 PM   #12
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Calibrating a kit zoom can be tricky. For example my 18-55mm front focused from 18 to 24mm and back focused from 30 to 55mm and the smaller aperture of the kit zooms can make it more difficult to read the results. I decided to calibrate for the longer angles and rely on manual focus for the wider angles.


Also you might find the suggestions in this thread about better focus helpful.

I also use center weighted spot focusing. i find it gives more consistent in focus images, except in the case of sports.

The lower image is a 100% crop
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Last edited by OldNoob; 02-17-2014 at 12:22 AM.
02-17-2014, 01:51 AM   #13
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QuoteOriginally posted by OldNoob Quote
Calibrating a kit zoom can be tricky. For example my 18-55mm front focused from 18 to 24mm and back focused from 30 to 55mm and the smaller aperture of the kit zooms can make it more difficult to read the results. I decided to calibrate for the longer angles and rely on manual focus for the wider angles.
You are far too close to your target. Which is fine if you are trying to set up phase detect focus for macro photography, although with macros you are better off manually focusing anyway.
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