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12-08-2014, 08:36 AM   #1
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PK_Tether and k-5 II

Hello everyone,
Very recently I can say that I'm a proud owner, of a K-5 II to be more precise.
I always like to deal on the used market, for this kind of 'stuff ' (and even more expensive gear like AV receivers or speakers), and photography being - so far although I have been paid - just a hobby, it makes even more sense. So, I bought a used K-5 II, instead of getting one of the K-5 IIs' deals, and saved around $200 cad, with which I bought a new (although I have waited and looked for one in the used market, even answered some posts mentioning one), a SMC DA 35mm f/2.4 AL... I just couldn't find anyone willing to sell me a used one, bought a used Tamron 28-75 that was probably a "lemon"... But that got me thinking, and that's why I started this thread.
What if it wasn't the lens that was the 'lemon', but the camera?
When I got my second DSLR, a Nikon D90, I thought I couldn't shoot and hold the camera properly because all my images were coming out "blurred", not sharp. But they were before, with the D3100... I started adding more lenses (a 1980's 70-210 f/4 that soon became my favorite lens) to my very extensive and expensive collection, of the 'old' 50mm AF-D that was offered with the camera, and was clear that it wasn't my technique that was in fault, it was the lens... The long zoom worked flawlessly, in all focal lengths and apertures. It was razor sharp. Sold the 50, bought another 50, hoping that this one would be 'good'. It wasn't and after some research I found out about micro-adjustments. Great, solved lots of problems., except for the D90, that didn't have the micro-adjustment availability, which "forced" me to upgrade to a D7000, which I didn't like, which lead me to consider the Pentax, ended up with a Fuji, and now I'm here... In just over one year.
Now, I read about this, and apparently the K-5's are known for this "issue"?
If, after the new 35 arrives, the camera still demonstrates the same behaviour, should I assume the camera has some problem? Solved with the PK_Tether solution?
Thank you in advance.

Kind regards.

Paul

Edit: more careful choice of words and it's order...


Last edited by Flugelbinder; 12-08-2014 at 09:17 AM.
12-08-2014, 10:26 AM   #2
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QuoteOriginally posted by Flugelbinder Quote
Now, I read about this, and apparently the K-5's are known for this "issue"?
I think you are worrying before you need to to. There is a reason that top end cameras have a focus adjustment utility. If when you get the lens thorough testing shows it to be off then use the AF fine tuning to put it into spec. The k-5 and later allows for up to 20 different lenses to have individual settings.

The k-5 had a reputation, built from a small group of posters who shot under specific conditions, of poor focus.. Especially low light with incandescent bulbs. That situation caused erratic and poor focusing results. But if you shot in daylight you really had no issues. The vast majority of users never had an issue. I could never understand what all the complaints were about, but I never shot in incandescent light so it did not affect me.

However, that was fixed with the k-5II, so it should not be an issue on your camera.
QuoteOriginally posted by Flugelbinder Quote
If, after the new 35 arrives, the camera still demonstrates the same behavior, should I assume the camera has some problem?
No. Just use the AF fine focus adjustment. However, you may not need it. On my k-5 almost all lenses needed some adjustment, on my k-5IIs I have not adjusted any of them. On the k-3 only one lens needed a very small (less then +1) adjustment and I just left it alone.

Also, if you do use the AF fine tuning be advised that precise, repeatable testing is required. Snapping a shot of a wall hand held is not a valid test. In any casual test the margin of error in the test itself is much larger than any possible error in the lens itself. You must use a tripod, a focusing target and be precisely aligned both horizontally and vertically. You must repeat the test multiple times, throw away outliers and average the results.
Here is an article that might help: Fixing Front and Back Focus - Introduction - In-Depth Articles

But honestly, I doubt there will be any issue. Once you get the lens do the testing and see, then worry. I test any new lens I acquire and have developed a standard process so I can repeat the test at a later time to make sure the results will be the same.

Edit: PS: I'm not sure why you mention PK_tether?? It is not needed for this the camera has an AF fine tuning utility built in.
12-08-2014, 10:44 AM   #3
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QuoteOriginally posted by jatrax Quote
I think you are worrying before you need to to... that was fixed with the k-5II, so it should not be an issue on your camera...
No. Just use the AF fine focus adjustment. However, you may not need it. On my k-5 almost all lenses needed some adjustment, on my k-5IIs I have not adjusted any of them. On the k-3 only one lens needed a very small (less then +1) adjustment and I just left it alone.


...Edit: PS: I'm not sure why you mention PK_tether?? It is not needed for this the camera has an AF fine tuning utility built in...
Good to know.
Thank you.

---------- Post added 12-08-14 at 10:44 AM ----------

I try the "3 battery" approach, it's been very useful, it's a very fast and simple, yet accurate way of doing a quick evaluation.
12-08-2014, 11:54 AM   #4
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QuoteOriginally posted by Flugelbinder Quote
I try the "3 battery" approach, it's been very useful, it's a very fast and simple, yet accurate way of doing a quick evaluation.
That is an excellent test to get a rough idea of whether there MIGHT be a problem. IMHO, it is not accurate enough for AF fine tuning. If you don't want to spring for the lens align, use a stiff metal ruler with fine engraved markings set at an angle. But make positive the camera is precisely aligned in both planes with the ruler. Off just bit and the test is invalid.

And seriously, messing with AF fine tuning without precisely accurate tests is likely to cause more harm than good. The error of margin in the test exceeds the potential lens error.

12-08-2014, 12:22 PM   #5
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QuoteOriginally posted by jatrax Quote
That is an excellent test to get a rough idea of whether there MIGHT be a problem. IMHO, it is not accurate enough for AF fine tuning. If you don't want to spring for the lens align, use a stiff metal ruler with fine engraved markings set at an angle. But make positive the camera is precisely aligned in both planes with the ruler. Off just bit and the test is invalid.

And seriously, messing with AF fine tuning without precisely accurate tests is likely to cause more harm than good. The error of margin in the test exceeds the potential lens error.
Absolutely.
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