[charchri4]

I'm shooting a K1 and last spring sold my trusty Tamron 70-200 to buy the MUCH more expensive Pentax version. I picked it up from Amazon and after a couple of months of most shots being out of focus I bought a second copy because I thought there was something wrong with the first one. The second one was worse..

I know it's not the camera because I have a Pentax 24-70 and a Pentax fa77 that both work flawlessly. I have tried different Focus settings in the camera and different settings on the lens and nothing I do helps. I'm to the point where I'm going to sell this dog and buy another Tameron but I thought I would put it out here to see if somebody had some advice on what I could do to make the Pentax lens work for me.

[pschlute]

I'm shooting a K1 and last spring sold my trusty Tamron 70-200 to buy the MUCH more expensive Pentax version. I picked it up from Amazon and after a couple of months of most shots being out of focus I bought a second copy because I thought there was something wrong with the first one. The second one was worse..

I know it's not the camera because I have a Pentax 24-70 and a Pentax fa77 that both work flawlessly. I have tried different Focus settings in the camera and different settings on the lens and nothing I do helps. I'm to the point where I'm going to sell this dog and buy another Tameron but I thought I would put it out here to see if somebody had some advice on what I could do to make the Pentax lens work for me.

Does it focus ok in Live View ?

Have you done a AF Fine-tune ?

[Paul the Sunman]

I call my DFA* 70-200 my Mandelbrot Lens, because it reveals more and more structure every time you zoom in closer. It is blindingly sharp on my K1. I believe that is the common experience.

It's hard to know what's going wrong in your case. Two dud copies is stretching credulity. You could try sending in the lens and camera for calibration.

[Dericali]

Yeah in my experience this lens has the best autofocus of any of the DFA lenses, including the 24-70 and the new 50mm.
As above, AF tune may be in order. I'd recommend also playing around and trying to figure out when it does work and when it doesn't. Are you using AF spot select mode? What sort of scenes are you missing focus on, e.g. portraits, objects close up?

[Adam]

Indeed, AF adjustments are specific to each camera-lens combo. Furthermore, with the shallow DoF at longer FL's, any inconsistencies might get exaggerated. As others have suggested, you can use live view to verify that the lens is optically sound, which would point to AF being the more likely culprit.

My recommendation would therefore be to calibrate the AF, methodically, using a suitable test chart. If this doesn't help, you can send in the camera and the lens, as calibrations are covered under warranty. Lastly, think about technique- a big lens like the 70-200 may require different handling than its smaller siblings.

[charchri4]

Thank you so much everybody! I'm shooting portraits, model shots, senior photos that sort of thing and generally at the longer focal lengths from maybe 120 to 200. I have always used single point spot focused and moved it around accordingly with the focal point being the subject face. With this lens so often I had a focus lock on the face but it would actually miss and hit whatever is behind the subject so I tried opening it up to 12 points and still moving it to focus on the face but that had no effect on image quality.
I confess I have no idea what calibrating a lens is about and have never done it on any lens because up until this 70 to 200 I have never had any problems.

[C_Jones]

I have a 70-200. It does an excellent job. If yours is under warranty, my recommendation would be as Adam said, send it in for a check up/diagnosis. Then if there is something that needs repaired or tuned, it will be done by a professional.

[charchri4]

Well I bought it in April and I did buy the extended warranty too so I suppose it's probably under warranty. Maybe I'll have the wife by a third copy and see what happens.

[aslyfox]

these articles might help the OP ( and others ):

Many enthusiasts spend a lot of money on camera gear and then want to know how good it is. While every experienced photographer can tell the optical qualities of a lens from fitting sample images there are ways beyond subjective quality evaluations. These are about testing lens sharpness and resolution using either an optical bench (which costs more than the average new car, so not really a good fit for "homegrown" testing), or shooting test charts and analyzing the results mathematically.
The article is about the latter: resolution testing at home using freely available test charts and software to analyze it.


Read more at: Guide: DSLR Lens Resolution Testing at Home - Articles and Tips | PentaxForums.com

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How Sharp are my Camera and Lens?
October 1, 2014 Leave a comment
You want to measure how sharp your camera/lens combination is to make sure it lives up to its specs. Or perhaps you’d like to compare how well one lens captures spatial resolution compared to another you own. Or perhaps again you are in the market for new equipment and would like to know what could be expected from the shortlist. Or an old faithful is not looking right and you’d like to check it out. So you decide to do some testing. Where to start?

http://www.strollswithmydog.com/how-sharp-camera-lens/

_____________________________________

Have you ever run in to autofocus alignment issues with one of your lenses? Did you know that even if you experience front- or back-focus with a lens, it's not necessarily defective?

In fact, more than 70% of the time, you can fix the problem at home without having to send anything in for repairs, or echancing any of your equipment!


Read more at: https://www.pentaxforums.com/articles/photo-articles/front-and-back-focus.html#ixzz5VcaOxF2g

___________________________________________________________

Fixing Front and Back Focus
Introduction
With the advent of digital photography we have become much more critical about focus accuracy. We're now able to enlarge our photos to 100% size on our monitors and look at them pixel by pixel. Inaccuracies in focus and other flaws which no one noticed or cared about in the film era are now blatantly visible.


Read more at: https://www.pentaxforums.com/reviews/lens-align-front-back-focus/introductio...#ixzz5VcadJ2Hy

[Dericali]

Thank you so much everybody! I'm shooting portraits, model shots, senior photos that sort of thing and generally at the longer focal lengths from maybe 120 to 200. I have always used single point spot focused and moved it around accordingly with the focal point being the subject face. With this lens so often I had a focus lock on the face but it would actually miss and hit whatever is behind the subject so I tried opening it up to 12 points and still moving it to focus on the face but that had no effect on image quality.
I confess I have no idea what calibrating a lens is about and have never done it on any lens because up until this 70 to 200 I have never had any problems.

Are you sure this is not a case of just the AF locking on the background because the background is higher contrast?

In my experience, this is one of the worst things about AF on the K1, it becomes apparent in certain conditions. Remember that the AF area is larger than the dot which you see in the viewfinder.

Going from single point to more points won't help. Are you using lights, and if so are they strobes or continuous?

Anyhow, now would be a good time to learn how to fine tune a lens... lots of videos out there.

[awscreo]

I have the same issue but with the Tamron 70-200) so each body + combo is unique in that way. Pretty sure fine tuning af would help a ton. I got inexpensive af tuning charts from amazon, they help to be more precise - Focusing Charts

[charchri4]

This shot is typical of what I am doing and getting. Shutter 1/250, f5 70-200 at 150 I was laying on a dock so camera was solid. file is not edited at all.

[charchri4]

This one is also laying on the ground to support things at 200mm shutter 1/400 and f4 with single point spot focus on her face. file is not edited at all and mind you the same body with either of my other lenses is dead sharp.

[charchri4]

This one the focus missed her and hit the background. Not too surprising with the distance using single point but I have 20 of them all the same issue and it rarely happened with my Tamron. 1/200 at f5 and 200mm.

[charchri4]

1/1600 sec f3.5 at 200mm