K-3iii: manual focussing using OVF

As will be apparent from my portfolio, much of my photography is devoted to close-focus/macro in the field and I often find myself resorting to manual focus when critical sharpness/creative DOF is critical. With every Pentax (Samsung) DSLR I have owned (GX-10, K20D, K5, and K3), all that has been necessary to ensure a high proportion of keepers when using this approach has been to correctly set the dioptre adjustment for the camera's focussing screen guide lines combined with the use of a magnifying eyepiece. With my recently acquired, and still 'testing/familiarising' K-3iii, however, this approach just does not work. Images shot with the subject 'pin-sharp' on the focussing screen prove not to have been, even when viewed at low magnification. By contrast, when using the camera's focus confirmation signal as a guide the vast majority of the resulting images have acceptable sharpness when viewed, despite them not appearing so on the OVF at the time the shutter button was depressed

Conscious that my experience might simply be one of life's strange coincidences, and not attributable to the characteristics/design of the K-3iii, I have compared the results obtained using the same lenses, subjects, distances, ISO/aperture settings and lighting and the differences are consistent, with accurate focussing using the OVF being possible on the K3 but not on its direct descendant.

Clearly, there are 'workarounds' such as learning to rely exclusively on the K-3iii's focus confirmation signals or adapting my technique and placing greater reliance on the use of live-view, but I am surprised that this should be necessary in order to enjoy the many advantages the camera offers over its predecessors.

My questions, then, are how common is my experience, should I be concerned that I might have purchased a sub-par example of the camera and, where others have found the same, what are the possible resolutions? In a thread discussing a similar problem on Pentax Forums, one suggested resolution was to 'calibrate' each lens (each day!) by using live-view to obtain critical focus and then switch to the OVF and obtain a similarly sharp virtual image on screen using the dioptre adjustment

Many thanks in anticipation of your considered thought/suggestions.

Jon

Interesting and helpful, Chris

Once set in this way, have you found that critical focussing using the OVF is possible irrespective of the lens attached and regardless of whether AF adjust has been dialed in on the camera for each specific lens?

Good point, Steve, and one that makes perfect sense in terms of what Chris has found to work well for him

Like you I've struggled to get the diopter adjustment right to show a sharp image in the viewfinder when the auto focus confirm is lit. With the K70 I just adjusted the diopter adjustment so that the viewfinder info was clear and that was fine for the image in the viewfinder. However this approach didn't work on the K3iii. What I have done is get the AF confirmation lit and then adjusted the diopter to give a sharp image in the viewfinder. Glad you have had the same problem as I thought it was just me. I do now check that the AF confirm is lit and not just rely on the image looking sharp in the viewfinder.

It could be that the mirror or the focus screen are out of alignment, or your dioptre adjustment technique is flawed. Get a sharp image in the viewfinder then switch to LV zoomed 100%. If they do not match then you know it is one on the three former problems.


The AF confirm is completely separate. It relies on the AF sensor. If the VF focus confirm (AF system) agrees with the LV, then your AF is working normally. If they do not agree with what you see in the VF then the fault is either :dioptre or mirror; or focus screen....or any combo.

A final thought for Jon....maybe your lens suffers from focus shift ?

[quote:3496ace15f="pschlute"]It could be that the mirror or the focus screen are out of alignment, or your dioptre adjustment technique is flawed./quote]

It's not that anything is out of alignment. As Chris, Jon and myself have found it is that the K3iii requires a different approach to setting the diopter adjustment. You cannot set the diopter by using the grid lines or speed/f number displayed in the viewfinder as I have done on all previous cameras but need to let the camera focus on an object and then adjust the diopter so the object is sharp in the viewfinder. To be doubly certain I now also deliberately look for the focus confirmation symbol. Because I don't wear spectacles when using a camera my diopter adjustment is nearly at its limits.

Very odd. So when you have adjusted the dioptre correctly for a focussed image, the gridlines/VF info display are not sharp ?

Correct. Just checking I have the diopter adjustment right on the limit and the VF info is not clear, it's as if the K3iii diopter adjustment has not got the same range as the K70. I'm going to change my approach and try keeping spectacles on and resetting the camera to suit that, see if I find that easier.

I keep my specs on

In my case, Peter, they are, but just not quite as sharp as they could, and would be, if the OVF was used exclusively with the camera in AF mode.

The dioptre adjusment needed to bring the subject, rather than the guide overlay, in to sharp focus when using MF is minimal (1 step difference for my 'shooting' eye), but the impact on the proportion of 'keepers' (viewed at 100%) has been dramatic, incontrovertible and consistent, without further adjustment, for every lens I have tried thus far whether of Pentax or third-party manufacture.

Were it not for this discovery and it's sharing on this forum by Chris and Paul I suspect I would have returned the camera to SRS (bless 'em) for a refund

BW

Jon

I imagine the K3III is the same as the K1. The grid lines/AF frame/Spot metering frame/crop frame are generated electronically. You can turn them on or off on the K-1.

you need to keep glasses on and if you have varifocal as i do that adds another problem as to which point to look through , near , middle or far. i tend to use the near portion as that is what i have to use to get clarity viewing the back screen, through ovf and monitor