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08-20-2013, 07:23 AM   #1
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K30 AF fine adjuctment

How does that work? And does it help?

08-20-2013, 09:07 AM   #2
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Um hm. Hello there. Focus is an important part of photography, something you cant really fix in photoshop.
When it comes to AF, there is a problem because both lenses and camera bodies are made to certain tolerances. So it can happen that the lens and body are on opposite extremes. In those cases, AF will consistently be a little wrong - front or back focusing. To fix that, you use AF fine adjustment (some call it micro adjust, AF adjustment, and so on).
You can find some threads and blogs that have tutorials on how to adjust it correctly. Basically, what you do is you use a tripod, and put a contrasty object at a certain distance from the camera (not at infinity, not at closest focus), and then you use AF. Then you switch to MF, and put the focus somewhere else and keep adjusting AF fine adjustment in the menu, until the AF is perfect. You should also use 2 sec timer, wide open aperture (lowest possible f-number) and reasonably low ISO (under 400)

You have to do this in good light, probably daylight.
I just realized that this explanation is not very good, but you can search the forums or internet. There are also some focus charts that you can download, print and use for this purpose. Just keep in mind that AF points are bigger than the little light overlays in the viewfinder. This is important, because sometimes the AF point simply locks focus on a different object than you want, but it is not really a malfunction, its just how AF works, because it focuses on the most contrasty part on the AF-sensitive area.

Oh, and some cameras only have a global AF adjustment, and other cameras also remember individual adjustment for up to 10 lenses or so. Not sure about K-30, feel free to look it up in the manual

Edit: I think you can get a free focus chart and some advice here:
http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.html
http://pentaxdslrs.blogspot.com/2012/01/front-or-back-focusing-problems-free.html

And I just saw another thread posted today with the same question, and it has a good answer. You can find it here. Hope this helps

Last edited by Na Horuk; 08-20-2013 at 09:18 AM.
08-20-2013, 09:20 AM   #3
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Not explained well? I understood what you said and that's all that matters to me. I will search the web for tutorials, and charts. Why I asked this question is that when I focus on an object, such as a lizard, his nose and the top of his head is not in true focus. I wondered it it was my lens or my eyes, even though I'm using AF with Center-weighed metering. Like the photo below:



Of course it could be the center-weighed metering doing this as I used to use spot metering only.
08-20-2013, 10:04 AM - 1 Like   #4
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Ah, focusing and metering are not the same. Metering refers to the lightmeter: how the camera measures how bright the scene is. Center-weighted is usually the one you want to use. Metering is what allows the camera to automatically give you the shutter, aperture, and ISO combination for a proper exposure, not too dark, not too bright.
The only things with AF to consider are AF.A, AF.C, and AF.S. C is continuous, which means it will try to keep the focus even if the subject is moving. It is often not very reliable and it takes some time to learn to get the most out of it. AF.S is the typical AF, you press the button and it will focus once. And AF.A is some automatic decision, where the camera switches between AF.C and AF.S according to what it thinks would be best.

Thats a great photo, btw. Its hard, if not impossible, to get perfect focus in such situations, simply because the DoF is pretty shallow and the subject might move at any time. You can increase the DoF by making the f-number bigger (narrower lens aperture). The DoF will also be more shallow when you focus "near", and it will be wider when you focus further away. Its a balancing act. For landscape photos with a wide angle lens, you usually get enough DoF by going between f8 and f16. In macro and close-focus situations, you often have to go above f16 to get the whole subject in-focus. The curve ball is that going above f14 or so starts to degrade image quality - the photo becomes less sharp.

But again, that photo is amazing. The only way to get more perfect focus is by doing it manually (which is very, very hard. Sometimes it can only be done in studio conditions)

08-20-2013, 10:24 AM   #5
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Thanks for the compliment. And yes, I know about DOF, I usually don't shoot below f8 if possible. And I used to shoot manually all the time. Now my eyes aren't as good as they should be and I have had to revert to AF. I don't like it, sometimes it doesn't focus on what i want it to focus on, and by the time it does focus, the bird, or lizard or bug is gone bye bye.
It was sunny where the lizard was and I didn't even think to change the DOF to f11 or better. Next time I'll try to remember. Old age is doing a number on me and I don't like it. LOL

Thanks for you help. I really appreciate these tips and ideas you give.
08-20-2013, 11:18 AM   #6
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What is happening is that the camera doesn't really know that you want to focus on the lizard's eyes so it focuses on where it thinks is best. In this case it looks like it focused on the centre of the image, the lizard's elbow (if its called an elbow). This happened either because it is manually set to choose the centre focus point or else it is the one it happened to chose. If I'm not mistaken when you set the metering to centre weighted it does actually influence the decision on which focus point to use putting more bias towards the centre one.

In any case there are various ways around it, depending on how dynamic the subject is.

1. Set the focus point to manual selection - this way you have a choice of 11 points to focus on which in many cases is enough for one of them to be in the right place. If not just recompose a little until you get one of the points in the right place and then select that point.

2. Keep it manually on the centre point, point the camera at what you want to focus on (the eyes in this case), half press the shuttter to focus and then recompose and shoot. The focus will remain fixed on what it was when you half pressed the shutter. (but make sure the focus mode is AF.S and not AF.C or AF.A). This is good for most instances but has some limitations when shooting macro as when you recompose you might actually move the camera nearer or closer to the subject. This happens even when using a tripod, at least with most types of 'ordinary' tripods. With most tripods the change in distance happens only when you recompose vertically, so you can avoid the problem if you only need to recompose horizontally.

3. For macro shots of subjects that do not stay still for any length of time - including lizards - my preferred method is to move just a little bit further and point the camera right at the point I want to focus on and shoot - then I recompose the photo by cropping. This of course loses some resolution but this is outweighed by the sharper focus obtainable this way. The photo below is taken that way.

4. Yet another way is to use manual focus and the so called 'focus peaking' in live view. This is great because it shows you all in one go all the parts of the image that are in focus by highlighting them with a bright outline. This is instantaneous so you can even use it on moving subjects and snapping as soon as the part you want is in focus. The downside is that focus peaking works only with the LCD on the back which in many situations, especially bright sunlight, can be difficult to see.

5. Another crazy thing that rather unexpectedly works quite often is to use the face recognition mode (only works in live view). I was surprised at in how many bugs, reptiles and other creatures the camera actually recognises as being their face. It is interesting and somewhat amusing to see it recognise a beetle's 'face' but I wouldn't really count on it.

Using the viewfinder to focus manually is not really an option in my opinion as it is not nearly accurate enough - at least not with the stock viewfinder screen.

In this photo I focused on the eye, but the focus turned out to be just a little behind that. That difference is what can be fixed by the focus fine adjustment. When I shot this photo I had not yet calibrated the focus for that particular lens. If I had then I'd have got the eye in perfect focus.

08-20-2013, 01:45 PM   #7
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lister6520. Thanks for the input.
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