As we know, the bells and whistles that are imbedded into the K-3 III when it comes to AF can be, well, are confusing.
"Do I use subject recognition? Zone, Full Auto, SEL-EX (S, M, L?), SEL, Spot, AF.S, AF.C" and the list goes on and on and on.
Through the past year of concentrated shooting to figure out all the ins and outs of this new to Pentax Marvel of AF, I'd like to help others understand what the camera is doing when set to certain settings and when you should use one setting over another.
Keep in mind that my findings are not endorsed nor has any info been provided by Pentax. This is solely my own trial and error over the many firmware updates that have been released.
Your mileage may vary which I will attempt to also explain why in this post.
Note I will be focusing on the latest firmware as of this posting (1.41). From my experiences, previous Firmware's (although improvements end over end) were spotty regarding reliability if you used any sort of tracking AF setting.
Okay! Let's begin...
We'll start by looking at the camera itself to show the correlation of AF point vs intended subject over a variety of scenes.
Full Auto with a busy scene
Here are all the settings that were used. Notice the AF red dot that shows where the camera placed focus.
Now let's zoom in and see EXACTLY where it focused in the scene itself.
So what the heck happened here?! Why is it out of focus when it clearly showed an AF point was used?
Well, there's a few things at play here.
For one, the AF points on the screen or in the OVF don't actually mean the subject is in focus.
They only show which AF point was active during capture (if any).
The 2nd thing is using the Type-1 AF setting (which links both the RGBir metering sensor and the AF system together).
I personally leave this setting on, but it's important to know what to expect when using it.
On the surface it sounds incredible! 307,000 pixels to assist the 101 point AF system for improved accuracy and speed in tracking? It's a no brainer right?
Well, not so fast. Yes it does track very well and very fast, however, 307,000 pixels don't divide that well into 101 AF points.
There's gaps between the 101 AF points which many times is the reason you'll get images that show no AF points were used at all, or you'll get a sharp image but the AF point is just off the target.
I think what's happening is that the RGBir sensor is telling the AF system where to focus but there's no actual focus point at that location so it picks the next closest actual AF point.
In other words, the RGBir sensor is picking AF locations that fall in the "cracks" between the AF sensors 101 points.
Now the 3rd thing is how busy is the actual scene? The subject recognition uses color, shape, and a database of pre-programmed things to recognize.
If the scene has many shapes and/or colors (especially if they're similar to the subject itself) it will make it more difficult for the camera to isolate the subject for focusing. This is especially true if using the "Full Auto" setting that uses all 101 AF points which is shown in the above picture (for this scene, Zone would be a better choice (if you wanted the eye detect AF to be more reliable).
Zone AF with a busy scene
Just like before, take a good look at the screen and note the AF point location
Now let's zoom in and see how it looks!
Well that's weird! Why is this one so much more in focus?!
By using Zone, you're limiting the area the camera will scan for moving subjects and things to focus on.
This is a great setting to use for complicated scenes with a subject large enough to fill most of or all of the Zone area.
Don't forget, you can also move the Zone around with the joystick just like using Sel AF.
Here's an example of using Zone with a subject on the smaller side of things.
And let's zoom in...
Well that totally failed. So, ummm, what happened this time?
Color information is too similar between both the subject and the background so it picked an AF point that it believed to still be the correct subject.
For better or worse, I made a video regarding the "PENTAX" folder that's in the SD cards, what some of the data contains and how it correlates to the subject recognition.
Surprise!!!! Clouds is one of the subjects! So if you're experiencing issues with maintaining focus on a subject when using Full Auto or Zone with a cloudy background, it's probably because the camera is recognizing more than one subject at a time and doesn't know exactly which one to stay latched to. Don't forget that both Auto and Zone AF allow for the recognition of eyes in the scene (as long as subject recognition is turned on).
So what settings should be used in AF.C to capture certain subjects since it seems to be really picky about everything?
It's not as complicated as it seems to be on the surface.
Larger subjects are tracked beautifully with no issues at all (Motorsports, birds in flight that take up at least a full 1/4 of the image area).
But wait!!! What about the shooting speed? Isn't a faster burst speed better?
Well, I've done a lot of playing around and analyzing this, and these are my findings...
The burst rate to use is actually determined by the speed of the subject you're trying to capture.
I know, say what? What does the burst rate have to do with the cameras focusing system?
Well, from all my field testing, it actually does, but not in the "traditional" sense.
The camera has a new predictive algorithm for focus targeting estimation and that's an important thing to understand.
For example, if you're shooting a car coming towards you at 100 mph (160 Km/h) and it's taking up approx 3/4 of the image area and you're shooting with continuous MED (7 fps), it's very possible for the camera to under/over predict the in focus location for the next shot. so the full 11 fps would get you more keepers as the camera better matches the subject speed with the "next frame" focus location. However, if the car is travelling at 40 mph (64 Km/h) and you're in full 11 fps burst, the AF location target will be a bit all over the map since the vehicle just isn't travelling fast enough for the cameras settings, so 7 fps would actually be the benefit here.
The same holds true for birds in flight. Faster smaller song birds require faster settings. Larger/slower birds require slower settings.
At the end of the day, the K-3 III is what I call a "deliberate" camera. You need to think about what you're shooting to apply the correct settings to maximize the keeper rate. Gone are the simple, meh, spot, single shot, I'll get something generalist approach. Now don't get me wrong, I know some of you are doing that and it's working for you, I'm not knocking it. I'm just saying that for more intense split second shooting, you need to apply some thought into the settings and base those settings directly to the subjects that you'll be shooting.
It took me quite a while to figure out what was going wrong because everything I did with my K-30 and K-3 just did not work so well with the K-3 III (to the point where I almost sent the camera back to get checked). But I figured there must be something I'm missing here so I just kept testing EVERYTHING to figure it out.
So, in a nutshell, smaller subjects erratic movement/faster motion = 11 fps.
Larger subjects with more consistent/slower movement = 7 fps.
Busy scene taking advantage of subject recognition: Zone AF
Isolated subject taking advantage of subject recognition: Full Auto AF (all 101 AF points).
Now, you can also use SEL S/M/L which I found does a great job of sticking with the subject under most conditions. It also allows you to start focusing from the center point before the camera will begin tracking.
Conditions where SEL M/L don't work seems to mainly be shooting subjects around water. I strongly think this (again) has to do with color information and the fact that the camera is a deliberate system as I explained before. When I'm shooting swans, ducks, geese out in the water, I switch to AF.S so the system won't try "finding" things that are moving.
It seems (to me anyway) that AF.C specifically "scans" for movement which causes AF issues such as jumping from the subject to something else moving. This is especially the case if the intended subject is barely moving but something else in the scene is moving more.
AF.S is how it's always been, so there's nothing new (except for Zone AF, the subject recognition and eye detection) that we aren't already used to.
Here's some more examples with the settings that were used.
Remember, where I've zoomed in is where the AF target is located.
Notice this one shows
No AF target but it's still sharp
I probably missed a couple of things here and there (I'm currently under the Covid weather)
but I hope this post helps at least one person out when coming to terms with the whizbangetry of the K-3 Mark III with all it's doohickies and whatchamacallits and how it all comes together into one amazing thingamabobber.
Last edited by Kobie; 04-07-2022 at 02:30 PM.