K-5 Focus Questions

David, I think a possible improvement would be to tweak the algorithm so the focus is much the same if approached from the long end or the short end. But even if it were possible technically do you suppose it would get past the marketing department? It would cannibalise sales. Improved focus accuracy is the only reason I'd consider buying a K-5II/IIs.

What is your view on the K-5II or the K-5IIs? Have you noticed any aliasing issues with your IIs?

I think the problems described in this post are the reasons I haven't tried to calibrate my lenses. There are so many variables (especially when using zooms), that it seems it could be an endless process. Not least the area covered by the chosen AF sensor could include areas at different distances from the camera.

I've sometimes been disappointed with general sharpness from my DA 17-70, at other times it's fabulous.

Hi Charlie

Firstly, as detailed on numerous posts recently, the K-5II and K-5IIs are in a different league to the Mk1 K-5 when it comes to focussing. The biggest issue I have with the K-5 is not so much the focus accuracy once calibrated, but the inconsistency. Sometimes it's off, sometimes it's accurate. The lower the light levels, the more pronounced the inconsistency.

By contrast, my K-5IIs is utterly reliable at focussing, in all light conditions I've used it in, including near darkness. It is truly magnificent at focussing; not lightning fast, but fast enough and unerringly accurate.

Regarding IQ, again the IIs is magnificent. It beats the K-5 (noticeably, although some will not believe this) and is the perfect tool where IQ is of importance, e.g. shooting weddings. I have never noticed any moire effect on any shots taken with it so far and I have taken thousands. In real world use, it produces more keepers and higher quality than anything else I've ever shot with. See a quick test shot tonight, ISO 1600, poor light, K-5IIs, Sigma 105mm DG EX Macro F3.2, no sharpening except whatever the in-camera jpeg applies.




Also, what is not often mentioned is that the rear screen on the K-5II and IIs is something to behold. Whatever Pentax have done to improve it, it has definitely worked. It is so good, there's no need for any other tool to review your shots, unless you have poor close vision.

Cheers
David

Thanks David. Do you also use zoom lenses or is it mostly primes? I'm wondering how consistent the focus is at various focal lengths and subject distances.

By the sounds of it a II/IIs could fix the problems I'm having with auto focus, but I'd like to try before buying.

Hi Charlie, I use both primes and zooms, mostly zooms unless I'm on a particular shoot where a prime is vital, like for example a wedding where the Sigma 105mm DG EX Macro has proved itself to be something of a superstar, particularly when fixed onto the K-5IIs.

My other main lens is the DA 17-70, again this has been used extensively at a couple of weddings on both the K-5 and the IIs. It is extremely noticeable that the 'keepers' with both lenses are a far higher percentage with the K-5IIs. I do agree to some extent that the focus accuracy with a zoom can vary a little at different focal lengths, but not to the extent you are finding. I wonder whether you have a problem with the lens? Once calibrated my zooms appear to focus accurately at any focal length and distance.

If you lived a bit closer I would be happy to go out on a shoot with you and let you use my K-5IIs - I think you would be impressed by its focussing capabilities and the quality of images it produces.

It is amazing how much better images look when they are in critical focus. Just a tad out and they are flat and ordinary.

Regards
David

Thanks, you've convinced me.

I suspect there's nothing particularly wrong with my 18-250 lens as I notice a similar focussing (or lack of it) characteristic with the DA*50-135.

Now it's a question of a II or a IIs. If it wasn't for the potential aliasing the IIs would be a no brainer. I wonder how often I'd hit a problem, given that my default aperture is the lens sweet spot and therefore more likely to occur. I always PP anything that's a keeper so hopefully in most cases it wouldn't be too much extra work to deal with it.

I agree, having played around in recent days with AF adjustment it's made me realise how images pop when they are properly focussed. I'm also impressed with what the mundane 18-250 travel zoom can deliver, if it's given a chance. In the past I've commented that it sometimes delivers a cracking shot but it's pretty hit & miss. I think I now understand why!

Finally, I wonder what the going rate is these days for a K-5 on 17k with 11 month warranty still to run. Sub £400?

I've PM'd you Charlie with hopefully what will be useful info, particularly on the K-5IIs moire issue (or should I say non-issue as there isn't a problem in real world use) and the DA*50-135 lens. Also, you should not experience any indifferent focussing with the 50-135 at any focal length; if you're having problems there must be something wrong with the lens, or the camera, or both.

Regards
David

Hi David,
What is critical focus and how does one achieve it? Thanks!

I'm not sure if this question in tongue-in-cheek, but I'll answer it as best I can. What I meant by critical focus is pin sharp in the right areas. It is achieved if the lens is good, is calibrated correctly to the camera and the photographer has focussed in the right place. Images that do not have this level of sharpness where it counts can look very flat.

An example of this would be perfectly sharp focus on the eye when taking pictures of birds.

Regards
David

I can assure you it was not, David!

My lack of experience, knowledge and skills was not obvious to you and others, probably!! But that's OK by me!

I find that you are one of the most helpful chap (amongst many) on the forum.

I learnt something new today, which leads me to my next question : how do I know if my lenses are correctly calibrated to my camera.

I have a K5-11s, 18-135 and 15mm.

Thank you.

That is a very good question and is not easy to answer. The only way is to test the lenses methodically. The way I do it is as follows:

1. Set camera up on a tripod

2. Get a subject that aids focussing, something like a cereal box with writing on it would be good, placed at a 45 degree angle to the camera

3. In the camera menu, make sure 'AF Fine Adjustment' is set to '0'; set the lens to its widest aperture and focus on a pre-determined spot and take a shot

4. In the camera menu, set 'AF Fine Adjustment' to '-10', take another shot and then set it to '+10' and take a further shot

5. Open all three shots at the same time in photoshop (or a similar program) and set the view to 'horizontal tiled view' so you can see all three images on screen at the same time

6. Increase magnification on the three images to the appropriate level so you can clearly see which text is sharp and which is not; it should be sharpest on the point you've focussed on. The '-10' shot should be focussed further back and the '+10' shot should be further forward

7. Continue this process by making adjustments to the 'AF Fine Adjustment' setting until you achieve the point where the lens is focussing sharpest exactly on the spot you are aiming at

Once calibrated, it's also good to take some test shots in a variety of situations to ensure the lens is performing correctly for normal shots. I also find that aiming at a textured surface at an angle (old bricks for example) is good for testing focus accuracy. If the 'AF Fine Adjustment' does not have sufficient leeway to calibrate the lens (which it may not have), you will need to delve into the K-5's 'Debug Mode' to make a bigger global adjustment. If you google 'K-5 Debug Mode' you will find ways of doing this, by using a program called 'PK_Tether' that you can download for free.

Hope this helps!

Regards
David

PS: If your lenses are OK, I doubt that your K-5IIs will need much adjustment. The K-5II models are very accurate focussers.

I much appreciate and thank you for taking the time to outline your method of calibration .

I'll have a go although the process looks beyond my technical ability!

However, you may well be right about doubting whether my camera needs adjustment!

I just needed to be sure that my equipment is functioning at its optimum! It's the OCD part of me!!

Kind Regards,
J-C