[rlmartindale]

Can you share some test target chart results for this. I am surprised you can determine any difference in AF/FA when focussing at infinity.

Here are some test shots of an 18-55mm calibrated for infinity. The macro shot of the ship model (another hobby!) is focused on the oars of the lifeboat.

Both full frame and approx 100% views are here.

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[kh1234567890]

* About 10m with my FA 77/1.8

That seems reasonable. For shorter distances (other focus zones) any extra fiddle factor offset needed should be read from the lens rom by the camera.

[stevebrot]

No particular reason to check this lens except to see if i was getting different results from infinity target or a closer target....

So we don't know what what we were correcting, only that we are happy with the results.

...Once the lens was set at infinity, the images are really sharp and very good at a variety of focus distances. It just works for me.

Thanks for the example images above. Good work on having built the ship model; I am impressed. I can only imagine the difficulty and attention to detail that doing something like that takes.


Steve

[stevebrot]

That seems reasonable. For shorter distances (other focus zones) any extra fiddle factor offset needed should be read from the lens rom by the camera.

My understanding has been that the "distance" numbers are used by the camera to help determine direction-to-correct to avoid racking the focus ring, but perhaps there is more. One of the quirks of ExifTool is that the tag names and translations (numbers to words) for makersnotes values are the developer's best guess as to purpose and significance. Sometimes they mix the mark, but usually they are helpful.


Steve

[wooly11]

I am in contact with Michael Tapes, who designed Focustune and he had me look for specific lines of code in the cam.dat file with my version of the software.

Sure enough, the Pentax KP was not there, but he has not yet advised how to fix it.

Here is the line of code he wanted me to find...

"Please find the file cam.dat in your installation. It is in a path 'Resources - data". See if this line exists in the file:

["pentax kp"] = { ["alias"] = "Pen-KP", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},

Please advise. Thanks."

Thanks Steve, That is really great, I have followed your instructions and the Kp is now recognized by the program and it finds the AFA information. I have only one trouble - I have sold the KP and waiting for the K3 III to arrive, so will have to add another line of code me thinks. But it is really great to at least having the programme working. - Big thanks
Edit - Have now added another line of code for the new K3 III so all should be well. I also note that the K1-II is not included, I would therefor suggest that the following is added to the cam.dat file.
["pentax kp"] = { ["alias"] = "Pen-KP", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},
["pentax k-3 iii"] = { ["alias"] = "Pen-K3III", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},
["pentax k-1 ii"] = { ["alias"] = "Pen-K1II", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},

[pschlute]

Here are some test shots of an 18-55mm calibrated for infinity. The macro shot of the ship model (another hobby!) is focused on the oars of the lifeboat.

Thanks for posting the pictures.

The shot of the bridge is not at all sharp and the subject is far too far away to make any guess as to what is the problem.

The shot of the model (nice by the way) is clearly not good either. I assume you used a tripod. Do you get a better image if you use LV to focus ?

[rlmartindale]

Thanks Steve, That is really great, I have followed your instructions and the Kp is now recognized by the program and it finds the AFA information. I have only one trouble - I have sold the KP and waiting for the K3 III to arrive, so will have to add another line of code me thinks. But it is really great to at least having the programme working. - Big thanks
Edit - Have now added another line of code for the new K3 III so all should be well. I also note that the K1-II is not included, I would therefor suggest that the following is added to the cam.dat file.
["pentax kp"] = { ["alias"] = "Pen-KP", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},
["pentax k-3 iii"] = { ["alias"] = "Pen-K3III", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},
["pentax k-1 ii"] = { ["alias"] = "Pen-K1II", ["fptype"] = "Pentax_1", ["afastatus"] = "skip"},

You are welcome...glad it helped....

---------- Post added 04-11-21 at 10:54 AM ----------

Thanks for posting the pictures.

The shot of the bridge is not at all sharp and the subject is far too far away to make any guess as to what is the problem.

The shot of the model (nice by the way) is clearly not good either. I assume you used a tripod. Do you get a better image if you use LV to focus ?

this is as sharp as that lens gets wide open......I did confirm the focus using LV and it matched.....keep in mind this was shot on a K7 at only 14meg per photo

[pschlute]

keep in mind this was shot on a K7 at only 14meg per photo

....and I am viewing on a pro-spec large wide gamut screen. Even so it can only display 3.7meg ! The K7 is capable of much better than that. I suspect you may have a problem with the lens. I shot with the 18-55 for a few years, it is not a great lens but not a bad one either.

People get really technical about precise angles and stuff when talking about this. My view is that we need to remember why we're doing the procedure. The trick is to be able to tell whether your camera and lens combination's point of impact equals the point of aim. To do that you need a surface that is sufficiently detailed and/or textured so that when you look at the picture, you can tell what's in focus and what isn't. You need it to be positioned so that there's a smooth transition from nearer to farther.
With a wide-open aperture to get the slightest depth of field, I generally use a four-foot ruler positioned at an angle (greater than 45 degrees) such that the angle of the camera and the angle of the ruler give me some front-to-back discrimination. (I don't bother to try to get everything on the same plane, which I regard as unnecessary). I figure when I see the numbers on the ruler get fuzzy at equal distances from what I aimed at, it's right. Or at least as good as it's gonna get.

[stevebrot]

People get really technical about precise angles and stuff when talking about this. My view is that we need to remember why we're doing the procedure. The trick is to be able to tell whether your camera and lens combination's point of impact equals the point of aim. To do that you need a surface that is sufficiently detailed and/or textured so that when you look at the picture, you can tell what's in focus and what isn't. You need it to be positioned so that there's a smooth transition from nearer to farther.
With a wide-open aperture to get the slightest depth of field, I generally use a four-foot ruler positioned at an angle (greater than 45 degrees) such that the angle of the camera and the angle of the ruler give me some front-to-back discrimination. (I don't bother to try to get everything on the same plane, which I regard as unnecessary). I figure when I see the numbers on the ruler get fuzzy at equal distances from what I aimed at, it's right. Or at least as good as it's gonna get.

One thing to remember is that PDAF "sees" stark vertical black/white boundaries best and when doing calibration, it is best to make the process easy on the machine. (Texture is a "bear".)


Steve

[rlmartindale]

.....u no...that 18-55 lens may be a bit off...did a quick check with another i had and it was a bit fuzzy....(not at all sure where that lens came from and it sharpens up decently...but, it may be a bit off)

.....this stuff fascinates me at some level....but, that also means i need to test when conditions are right....bright sunshine and no wind....

....so, in the future....test lenses only when conditions are just right....stay tuned...(its overcast and sunny with wind today, for example....that won't work)

[rlmartindale]

So, I tried both my 18-55 zooms on a KP....one is an L version with what seems to be a screw drive focusing while the other uses SDM? (not sure about this) (also removed the filters from the front...that may have been adding some reflections)

However, BOTH lenses did not work well in Focustune, with results that looked like waves instead of slopes so the readings at +10 were sometimes the same as -5, widely varying readings and warnings that not enough photos were sharp....just did nothing right. EV was 9.6 so there was plenty of light.

So, I ended up setting them to 0 (ironically after all this effort) and shooting an infinity shot and a shot about as close as that lens can do....and whatever secret sauce Pentax is building in the lens resulted in very sharp images from both. Examples on request.....

(BTW....my infinity testing of the lenses showed -2 and +2 as the result, with almost no change from either lens no matter what the AF setting was, so setting at zero was very close)

[noelpolar]

I've been known to use dead people to help....

[rlmartindale]

I just finished reading a good discussion of the location of the focus testing (i.e 25x, 40x focal length, infinity, whatever you want). They made the point that focus tweaking like this and for the default values, can only be optimized for one distance.

The suggestion for 25 or 40x focal length is just that...a suggestion to get you a good mid value for that perfect focus.

However, it seems to me that the lens manufacturers START at infinity and work their way back...they have to. So, it still makes some good sense to me to get an infinity target that is clean (tougher than you imagine with trees , powerlines, etc.) and calibrate the lenses from that.

I intend to try my best to do that testing right and see how the PICTURES turn out...imagine that....

[35mmfilmfan]

I've been known to use dead people to help....

Since this was on private property, did you get a signed model release from each participant ?