[BruceBanner]

Now hear me out... I would also like to point out that I am not standing by this statement per se, rather I am putting my own observations out there to see if anyone else feels similarity or disagrees wholly etc.

I recently underwent another afternoon of fine tuning my adjustments for various lenses following standard Focus Chart protocols, perhaps more importantly I was repeating how I was performing the tests like it did last time (some 6-12 months ago).
Before I began fiddling I noted down what my previous focus chart testing results were (Looked at 'Apply One' with each AF lens etc). This time round all my testing gave different results, quite massively so in fact. Some lenses were +3 for the old Apply One, but now this recent test told me -7 was better... which just leaves me to believe how accurate can these tests really be if repeating them on a different day (trying to replicate the exact set up as possible) leads to pretty drastic FA (Fine Adjustment) changes. Can the camera change over time, or is it simply impossible to replicate the previous Focus Chart set up so that the FA settings come out very similar?

This was my first warning that Focus Charts were not doing the job for me. If I can't (get consistent results) with tripods and a controlled set up (on different days)... then what's in the field shooting really going to be like?

I also noted that there is a massive difference in results depending upon whether I use a 2 sec timer vs not. It didn't matter if it was a FA 50mm@1.4 or a MF Samyang 85@1.4, just the very act of touching the shutter lightly and pressing it down shifted the focus point slightly off centre (compared to using a timer) which then again made me question the validity of the Focus Chart process (because then the FA for each way varied tremendously).
I mean... fine, I have fine tuned my lenses to be accurate for when I have them tripodded up, shoot with timer and aim at fairly close range targets... like I do that kind of shooting a lot in the field... not....
So what am I FA my lenses for? A scenario I rarely replicate in the field, or should I be FA my lenses for actual shooting conditions that involve me being still as I can, handholding, SR on, squeezing the shutter button gently and not in timer mode...
Shooting f1.4 with a 50 or 85 has a huge amount of deviation in where the focus is lies, tuning it for a tripod and timer scenario seems pointless to me, once you try those settings in the field in your hand, SR on.. I find the FA irrelevant.

Furthermore, this was the first time I tried FA for MF lenses (like the aforementioned Samyang 85/1.4). What I learned here (and was more obviously apparent) is that the AF confirmation is not a single quick point in a range, but actually a range itself. You can focus from near to far, green AF hex comes on, continue to focus (and the green hex confirmation is still showing as being in focus) until you continue to focus so much that it toggles off.... so what then... where do I fine tune my FA to be? If I focus from Far to Near it's a massive difference from Near to Far.

I tried to draw what I felt was happening (and this related to CIF, but the principle is perhaps the same?);



So when trying to FA for a MF lens... it seems nigh impossible, unless perhaps I try and FA for one end of the spectrum, either FA for when focusing from Near to Far, or Far to Near... but even when I tried doing either of those two things it was really hit or miss.
In the end I put an empty beer bottle on my mailing box and took pics with the FA and felt none of them really improved anything (not with the AF lenses or MF). With MF lenses I was just better to use my eye and then take the shot, 100% completely ignore the focus confirmation. Trusting it would result in more fuzzy shots than just using my eye, seeing when I felt the text on the bottle was at it's crispness and then shoot.
Additionally, I noted that sometimes Auto Focus confirmation wouldn't even 'come on' at all, panning away, depressing the shutter and trying again, nothing worked, actually turning the unit off and back on again seemed to 'kick it up the arse' to presenting the Auto Focus confirmation again... so it was quite erratic as to whether it wanted to be used or not :S

With AF lenses I had to change the FA, none of the settings I had used in a Focus Chart were relevant now that I am handholding it out in the field with SR etc.

So... this really begs the question... are Focus Charts then a complete waste of time? My conclusion is that I have a better shooting experience with trusting my eye with MF lenses and with AF lenses do the FA for in the field scenarios.

What's everyone's stance on this?

Cheers,

Bruce

[AggieDad]

Bruce,

You carefully and fully explained what I have experienced with my own forays into focus adjustment. Spot on today. Spot off tomorrow. Maybe none of our (yours and mine) lenses are bad enough to worry about.

The good news is we both have really neat $60 plastic printed thingies – who else in the neighborhood can say that?

[swanlefitte]

I thought focus confirmation was only good to f2.8. Might trying at f1.4 be the problem? I don't know enough.

[Alex645]

So... this really begs the question... are Focus Charts then a complete waste of time? My conclusion is that I have a better shooting experience with trusting my eye with MF lenses and with AF lenses do the FA for in the field scenarios.

Bruce

Focus Charts are not a complete waste of time. If your lens/camera combo needs a baseline FA adjustment needed, using a focus chart will help you to FA to eliminate FA as a possible cause of focusing issues. BUT keep in mind the results of a test is only as accurate as how it was done.

There is no universal best way to focus for all photographers. And there is no singular best way to focus (MF, AF with quick shift, phase detect OVF single vs continuous, contrast detect EVF/Live view, using AF back button, etc). It all depends on the photographer, the subject, and the shooting conditions.

You have done the right thing in trial and error to come to a conclusion of what works best for you.

I don't use focus charts often, but I find them helpful when acquiring and testing a new lens, or if a problem develops and I need to troubleshoot the cause. But just as frequently, I will use real world subjects for my testing instead of a studio with a tripod at a prescribed distance from the subject with a focus chart.

[clackers]

The PDAF modules in the world's cameras are only rated to f2.8, aren't they?

We're always asking more of them, and at f1.4 the depth of field on something within a metre is almost non-existent anyway, right?

[BruceBanner]

I thought focus confirmation was only good to f2.8. Might trying at f1.4 be the problem? I don't know enough.

And that's what I thought too, so I did further testing at more stopped down apertures but I found the same thing apply, one scenario for a Focus Chart situation makes for a different FA adjustment needed for 'real world' shooting conditions. In fact this added to the confusion and distrust in the Focus Chart system as at different apertures the FA value seemed to alter! I actually need the FA focus the most when shooting very wide open, at f2.8-f5 the field of DoF is more forgiving anyway, so I always tried to FA for the more tricky DoF namely wide open or close to.

Focus Charts are not a complete waste of time. If your lens/camera combo needs a baseline FA adjustment needed, using a focus chart will help you to FA to eliminate FA as a possible cause of focusing issues. BUT keep in mind the results of a test is only as accurate as how it was done.

There is no universal best way to focus for all photographers. And there is no singular best way to focus (MF, AF with quick shift, phase detect OVF single vs continuous, contrast detect EVF/Live view, using AF back button, etc). It all depends on the photographer, the subject, and the shooting conditions.

You have done the right thing in trial and error to come to a conclusion of what works best for you.

I don't use focus charts often, but I find them helpful when acquiring and testing a new lens, or if a problem develops and I need to troubleshoot the cause. But just as frequently, I will use real world subjects for my testing instead of a studio with a tripod at a prescribed distance from the subject with a focus chart.

So my argument is that Focus Charts are a waste of time, but absolutely not FA. I can place a bottle on a wall and use AF and have -10 or +10 for FA and will indeed get consistent OOF shots etc, FA definitely works and does 'stuff', it's just that using the Focus Chart set up doesn't correspond to what I find I need in the real world. I have found I get much better accuracy and success in testing and adjusting FA shots with a 'beer bottle on the wall' test, I take this as my FA values (and indeed they seldom match what I set on a Focus Chart)... so then why bother with Focus Charts at all? Just get out there, have that beer, place that bottle on yer wall or mail box and test and make adjustments, that's the conclusion I'm coming to.

[Alex645]

So my argument is that Focus Charts are a waste of time, but absolutely not FA. I can place a bottle on a wall and use AF and have -10 or +10 for FA and will indeed get consistent OOF shots etc, FA definitely works and does 'stuff', it's just that using the Focus Chart set up doesn't correspond to what I find I need in the real world. I

Understood and for sure real world tests are all that truly matter.

Focus charts just have the advantage of quantifying results. X millimeters front or back focused vs. the side edge of the beer label or the bottle cap in front of the bottle.

[K(s)evin]

Since 2009 I have owned the K-7, K-5, K5lls, and the K-1. Through that 9 year, 4 camera span, I have never fine tuned any of my lenses. Over that time, I believe that I have developed a "feel" for Pentax auto focus. I notice the incremental improvements to the AF while using each body, and try to adapt myself to each camera. If proper focus is not achieved, I mark it up to "user error". Autofocus is great (usually), but it is not perfect. I use my eye through the viewfinder as the ultimate judge. Sometimes that fails me also. An autofocus system gives you that systems' best guess. I like to try to verify that "guess" with my eye before I hit the shutter.

[pentaxfall]

Focus tuning is a precision work. Ideally it should be done in a lab environment. Lab can consistently maintain same distance between camera and target. They can also maintain the light source same. If all these factors are same, then same camera should give same result on 1st and 2nd day. Our home test setup lacks consistency and precision so the result fluctuates. So I do not blame the focus card

Even though it is not 100% accurate it is good that consumer test their lens because if number of warrentee repairs increases then camera makers may tighten their QA, otherwise they have no incentive. I recommend people test their lens.

[BruceBanner]

Focus tuning is a precision work. Ideally it should be done in a lab environment. Lab can consistently maintain same distance between camera and target. They can also maintain the light source same. If all these factors are same, then same camera should give same result on 1st and 2nd day. Our home test setup lacks consistency and precision so the result fluctuates. So I do not blame the focus card

Even though it is not 100% accurate it is good that consumer test their lens because if number of warrentee repairs increases then camera makers may tighten their QA, otherwise they have no incentive. I recommend people test their lens.

Good point, so the validity of Focus Charts then lies solely with testing for defective lenses and not actually to carry such FA into the real world as they seldom apply? That's perhaps the conclusion I am coming to.

[pschlute]

perhaps more importantly I was repeating how I was performing the tests like it did last time (some 6-12 months ago

Are you using the same light ? Artificial light can affect the results.

I was repeating how I was performing the tests like it did last time (some 6-12 months ago

Are you testing each lens 10 times (making the camera focus each time from an extreme) and using the "majority vote" for your FA setting ? A single test is unreliable.

Can the camera change over time

I guess it is possible for both camera and lens to change characteristics over time, although I have never seen this.

I also noted that there is a massive difference in results depending upon whether I use a 2 sec timer vs not. It didn't matter if it was a FA 50mm@1.4 or a MF Samyang 85@1.4, just the very act of touching the shutter lightly and pressing it down shifted the focus point slightly off centre

Test by making the camera achieve autofocus and then turn off AF before you take the picture, otherwise using 2sec timer will cause the camera to AF again. a 1.4 lens can give you "focus shift" so extra care is needed when calibrating a wide lens such as these.

so I did further testing at more stopped down apertures but I found the same thing apply

Stopping down a lens will not affect AF accuracy, it focusses at widest aperture only.

From my experience using AF-FA for manual lenses is not reliable. The green hexagon confirmation zone is too wide.

[LensBeginner]

As for the part where you said "touching the shutter lightly", I suggest you set the 2s timer when using the tripod or, alternatively, use a simple TV remote and select the IR remote shooting mode.

As far as focusing is concerned, I've had surprises with long lenses - especially zooms - where I had focus shifts at the longest FLs, mostly around f/8, so I'd check that focusing was consistent on the whole range first: this is of course done with a test chart, focusing manually in magnified LV wide open, then stopping down keeping the Optical Preview button depressed and checking if the focus shifted.

[stevebrot]

Focus tuning targets are useful, though correct use requires more trouble than many are prepared to deal with and not all targets are created equal or have appropriate instructions. As you noted, the usual precautions for capture optimization (remote control, 2s delay, electronic shutter, etc.) make a difference. It is also very likely to get very different results on different runs or whether focusing up or focusing down. The better tuning solutions use a statistical approach to evaluate the need to tune and they do so because PDAF has fairly poor precision overall and much worse repeatability with lower contrast lenses. I have not looked at what the state of current resources for doing AF fine tuning are here on PF, but it may be a review.

Stopping down a lens will not affect AF accuracy, it focusses at widest aperture only.

Excellent point! Similarly, it is important to evaluate AF testing at the same aperture used for testing. Yes, focus shift does happen, but AF fine tuning assumes it is not happening. Go figure...

From my experience using AF-FA for manual lenses is not reliable. The green hexagon confirmation zone is too wide.

You are correct, though the problem extends to AF lenses too. Focus sensitivity for PDAF is fairly poor with resulting poor precision. The main problem with testing manual focus lenses is that with a very few exceptions (two Irix models), per-lens AF tuning is not possible with other than AF lenses.

In regards to doing focus evaluation and fine tune attempts for manual focus lenses, @BruceBanner was doing some experiments with using/changing global focus adjust with these lenses. I did a little research on my K-3 (may not generalize to newer bodies) and was shocked to find that changes to global may affect ALL single lens adjustments. I have not posted my findings because I wanted to confirm, but in short, what I did was apply a valid -3 fine adjustment for one of my AF lenses and then set a +10 adjustment globally. The -3 was overridden by the +10, but only in terms of AF behavior. The numbers stayed the same. Resetting the -3 returned it to it previous appropriate tune for that lens. Playing with global has the potential to screw up the single lens tuning. I still need to confirm a few more test cases, but for now, I am thinking that global AF adjustment may be evil.


Steve

[stevebrot]

As for the part where you said "touching the shutter lightly", I suggest you set the 2s timer when using the tripod or, alternatively, use a simple TV remote and select the IR remote shooting mode.

Good advice. It is too bad that few phones have IR blasters at present. My Samsung S5 was one of the last and I very much appreciate that feature when I need a remote and don't have my cabled version with me.


Steve

[LensBeginner]

Good advice. It is too bad that few phones have IR blasters at present. My Samsung S5 was one of the last and I very much appreciate that feature when I need a remote and don't have my cabled version with me.


Steve

My dirty cheap Redmi Note 3 Pro has it... I rarely use it, but there's a DSLR remote app you can download from the market