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05-25-2016, 01:43 AM   #16
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Once you figure out what the AF adjust actually does, you won't spend frustrating hours of futile fiddling and tweaking, especially with third party lenses which for whatever reason do not communicate the correct offset data based on focus distance and focal length to the camera body, ever again.

05-25-2016, 07:58 AM   #17
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QuoteOriginally posted by Culture Quote
It seems like the complete must is the general concensus. But the task is daunting for me.

My tamron 28-75 2.8 seem soft for my liking compared to its big brother 70-200 2.8. I am wondering if its front focusing
I just want something simple to test my suspicion.
Try this quick test on a carpet, tablecloth, or any textured surface

-Put something with good contrast on the floor / table that's large enough to completely cover the focus point.
--- (Something like a box of tissues with a detailed pattern works great!)
-Position your camera so that the vertical face of the object is perpendicular to your camera at the distance you usually place your subject.
-Focus on the vertical face of the object so that the focus point is definitely on the object, but close to the edge.
-Focus and take a picture
-Focus on your hand, then refocus on the object and take another picture (this forces the camera to adjust the focus again since it might not move if it thinks it's close enough) - repeat for a few pictures.
-Look at the pictures. Your object should be in focus, and you should easily see where the center of focus lies on the carpet or tablecloth.
--- If the center of focus is behind your object, you need to use positive adjustment.
--- If the center of focus is in front of your object, you need to use negative adjustment.

This works the same way as tests like this or that but you can do it anywhere with any object on a textured surface. It's not quire as accurate as setting up a tripod and going through the whole process, but it's a quick way to find out if your lens has major focus issues and try a rough adjustment.

You'll still have to go though the long process if you want to fine tune it accurately though.
.
05-29-2016, 05:10 AM   #18
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Could you guys quickly remind us, which software easily reads AF Fine Adjustment data (values, from -10 through 0 to +10) from picture Exif file?
I cannot read adjustment data with IrfanView ($E, any hint from you?) nor with Pentax Digital Camera Utility 4 / Ricoh Digital Camera Utility 5 (am I doing something wrong?)
I believe my K-3 with 1.21 firmware writes AF microadjustment camera/lens data into Exif.
I have strong back-focussing with most of my Pentax lenses.
05-29-2016, 11:09 AM   #19
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05-29-2016, 11:31 AM   #20
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QuoteOriginally posted by UncleVanya Quote
Infinity isn't the recommended distance for AF fine adjustment typically.
There are several forum members who are of strong opinion that infinity (or close to it) is the only valid distance for focus calibration and/or lens testing. Good luck, I say... *


Steve

* Both the optically and mechanical precision approaches zero as distance approaches infinity...
05-30-2016, 12:34 AM   #21
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QuoteOriginally posted by kh1234567890 Quote
ExifTool
Is ExifTool easy to install in Windows (XP)?
05-30-2016, 02:38 AM - 1 Like   #22
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QuoteOriginally posted by Prakticant Quote
Is ExifTool easy to install in Windows (XP)?
Very easy to install, update and remove. Get the executable from here. Unless you are happy with using just the command line interface I'd recommend also downloading the GUI from here. Should you have any problems running it then the ExifTool forum regulars are very friendly.

It will read and decode all known EXIF tags. AF adjustment is under MakerNotes :
Attached Images
 
05-30-2016, 03:02 AM   #23
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QuoteOriginally posted by stevebrot Quote
There are several forum members who are of strong opinion that infinity (or close to it) is the only valid distance for focus calibration and/or lens testing. Good luck, I say...
All that the AF adjust does is to compensate for tolerances in the camera body (global adjust) and lens (lens adjust) mount thickness. Corrections for focus distance zone and focal length (for zooms) are held in the lens rom and for Pentax lenses are not easily user alterable.

My personal experience - and it is your prerogative to disagree - is that misfocus at infinity annoys me the most and that in practice setting the AF adjust at infinity results in my lenses also focusing correctly at other distances. Try it.

05-30-2016, 06:08 AM   #24
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There are actually many methods you can try. I think there are some threads about it already. But they all require at least some time and effort. Thats just the kind of thing this is

QuoteOriginally posted by Adam Quote
If you're not having any issues with your lens, just leave the adjustment setting alone. Unless you're working with a very shallow DOF chances are that a small inaccuracy will have no practical effect.
This is also important. If you are shooting at narrow apertures, like f8, then the AF would have to be really wrong for this to be noticeable. Though, it does depend on the lens.
05-30-2016, 06:57 AM   #25
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What I do is a bit tedious but it has worked for me..

1) set camera and lens on sturdy tripod, fixed at a subject at infinity range (with high contrast), on single/center focus point in the center.
2) set camera drive mode to self timer 2 seconds
3) adjust AF micro adjustments to -10
4) set camera lens to minimum focusing distance
5) gently press shutter release button to let camera autofocus and take photo
6) increment AF micro adjustments by 1
7) goto step 4

I do this all the way to +10 being very careful not to hit, touch, or even breathe hard on the camera as to upset the positioning.

After that, I take my test shots and load them on my PC. I then go through in an image viewer (In my case, ifranview with position and zoom level locked on my focus point) 1 by 1, and back and forth between, until I find the one that is sharpest at 1:1.

Note: you must lock the position and zoom level so you can cycle through them at the same spot at 1:1 otherwise it is going to be very difficult to discern between different shots. Then I use the keyboard arrow keys to cycle back and forth.

Finally, after I have concluded which one is the sharpest, I load that in Exiftool for Windows and find out which AF microadjustment meta value is set for it.

Then I set that in the camera. voila.

---------- Post added 05-30-16 at 09:05 AM ----------

Also, for zoom lenses, currently with Pentax AF micro adjustment feature we only get 1 AF adjustment for the whole focal length range. Therefore, what I do is zoom to the end that I use the most and adjust for that.
05-30-2016, 08:44 AM   #26
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QuoteOriginally posted by mee Quote
4) set camera lens to minimum focusing distance
This is an important step !

It is also useful to take a shot carefully focused in expanded live view, to get an idea of what you are aiming for.
05-30-2016, 10:07 AM   #27
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One thing I forgot: set the aperture to as large (smallest aperture number) as it will go at your intended focal length. You want the least depth of field possible to really hone in on where the lens is truly the sharpest.

If you're shooting at f/5.6 or f/8 then it might be difficult to discern correct adjustment.. increase it to f/4, f/2.8, or even larger if possible.
05-30-2016, 02:31 PM   #28
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QuoteOriginally posted by kh1234567890 Quote
All that the AF adjust does is to compensate for tolerances in the camera body (global adjust) and lens (lens adjust) mount thickness.
I believe you are misinformed, but that is OK. As for the doing the adjust to infinity...If it works for you, cool.


Steve
06-06-2016, 12:30 AM   #29
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QuoteOriginally posted by kh1234567890 Quote
It will read and decode all known EXIF tags.
Any idea how to read K-3 AF Micro Adjustment EXIF tag with IrfanView (if we knew $Etagnumber?)?
Actually what pisses me off with Ricoh/Pentax their Digital Camera Utility (v. 4/v. 5) does note read this AF tag
06-28-2016, 07:22 AM   #30
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QuoteOriginally posted by mee Quote
1) set camera and lens on sturdy tripod, fixed at a subject at infinity range (with high contrast), on single/center focus point in the center.
Question:
Perhaps I'm overthinking this? I have only had one cup of coffee so far so I apologize if this question is "dumb"...

How do you fix a subject at infinity range?
I understand hyperfocal distance, but is this where I need to setup my subject?

I calculated for my DA*300 on a K-3ii that HFD is 3691.9 ft. There's no way I'll setup a subject at that distance!

To even reach the far limit of acceptable sharpness at infinity from 300mm my subject has to be a minimum of 2696.62 ft with a near limit of 1558.4 ft.

Am I overthinking this?!

I was planning on setting up my camera + lens on a tripod at one end of a football field and place a magazine on the fieldgoal post of the opposite endzone. Isn't this far enough for infinity focus, or not for 300mm?

Last edited by UserAccessDenied; 06-28-2016 at 07:52 AM.
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