Should you send in your new body for tuning? SLR no more?
I had a Samsung GX10 which is a Pentax K10D. I own a Sigma 17-70mm f/2.8-4.5. When I first bought it several years ago it was obvious it was de-centered at 70mm. It came back from Sigma fine at 70mm but de-centered at 17mm. I sent it in again. Sigma asked for my camera and found my camera needed AF tuning. I argued to no end that all my other lens are fine, how can it be that my camera need AF tuning. A few days latter my lens came back express mail and it was a new lens because I could see the serial number tag falling off this lens performed good IMO at the time, but still a little rough at 17mm f/2.8, but good enough. My GX10 died, Samsung just gave me another instead of repair. Now my Sigma 17-70mm was perfect it behaved exactly like the blur charts on SLRgear shows it should. Go figure Sigma was right my body AF was off even though my other lens were fine on it.
I made a switch to a K20D. All my lens were OK only my Sigma 17-70mm needed +3, Pentax DA18-55mm WR +8, AF fine tuning. I have owned 3 kit lens. Pentax original, ver II and now the WR version of the DA18-55mm kit lens. Of them the last (WR) was worse in image quality. I did do AF fine tuning so it was not focus (at least I thought). I sent it to Pentax (CRIS in Arizona) it came back saying it was within factory spec. So I never really liked the image quality below about 35mm.
I sent my K20D to CRIS in Arizona I was specific in the repair and what I wanted checked. I never wrote AF as I thought it was fine. Last year I could do BIF with good results. It came back with a note saying AF was adjusted. So I checked AF fine tuning (which I do almost monthly) and focus was changed. I could now almost just shut off AF fine tuning but for one lens, the DA55-300mm ED, it now needed +5 tuning and before it needed no tuning. So the AF system is much more adjustable and more sensitive than I know. Some conclusions of my experience over the years.
A new camera is not necessarily in perfect factory spec. Also you can’t tell by any means if the body needs adjusting or if it’s the lens. Me you just don’t have the service equipment and our logic is flawed, e.g. if 20 lens need no AF tuning and one needs -10 tuning that lens is out of factory spec and the rest fine; no it could very well be the body!
I have taken 49000 pics with my K20D almost 40000 with my GX10. During the time I had them AF never changed e.g. the Sigma 17-70mm was always best with +3 AF fine tuning, the DA18-55mm WR was always best with +8 (or more really) AF fine tuning. Nothing changed with AF when new up to service time. You can take my word BB/FF checked by me all the time.
Some patterns I see. All manufactures have this in common. The higher the mega-pixels the more problems (maybe). Folks use logic as shown above to determine which part of the system is flawed. Its obvious to me this logic is flawed, you can’t figure out if it’s the body or lens that needs adjusting even if buying a new lens! The Pentax owners manual tells you to send in your dSLR every year or two and it should be followed.
Another pattern SLR AF systems need precision tuning beyond which manufactures can implement for mass production (economically) for enthusiast consumers. Moreover lens can be said to be the same needing precision beyond economic reason because of the dramatic increase in resolution since digital. Digital has increased the demands of factory tuning thousands of times versus film partly because of “Pixel-Peeping”. To make matters worse digital sensors are un-forgiving by another factor of thousands of the light coming out of a lens; film could care less about very slight alignment issues compared to digital. One would think with this analysis that we should be plagued by AF issues. We are IMO read Nikons, Canons or anyone’s forum with APS dSLRs.
Look at the pics below for example. The first pic is the DA18-55mm WR taken at 18mm f/3.5 notice there are soft spots here and there. This is why I sent it in and Pentax (CRIS Arizona) said it was fine “within factory spec”, I thought wow what poor factory specs. Further tuning did help with my K20D. But the first two pics are exactly what I got each and every time, no exceptions. Note at 18mm f/3.5 its pretty soft in the corners even some softness at f/5.6.
Now look at the very same lens on my K20D hand calibrated by a tech. There is no major softness even at 18mm f/3.5!!! NOT LOGICAL CRAZY NUTS , how can this be. Now stop down to f/5.6 and its darn near tack sharp corner to corner. The lens now does this each and every time. Go to f/8 and there is no reason for me to carry the bigger more heavy Sigma 17-70mm. You tell me.
My conclusion is for economical high performance enthusiast type cameras, mirror-less is the only way. I say this with great reluctance as I really enjoy bigger SLRs but whats the reality.
The before AF tune pics were developed today from DNG to JPEG to in Pentax DCU 4 with Bright setting to match the newer pics and keep it more fair. The new pics are hand-held out of K20D jpegs set to bright (factory defaults).
DA18-55mm before body calibration
After body calibration at CRIS Pentax
18mm f/5.6: stopped down more there is no reason to carry the Sigma 17-70mm
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|Jul 10, 2011|
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