Action Autofocus - Just Not Getting It

**david94903** · 08-20-2018, 08:30 PM

Originally posted by Wingincamera

There are various ways to check & adjust the fine focus adjustment of your lens. I stumbled upon the DotTune method and find it really easy.
dot-tune method - Bing video

That's an interesting method, had not see that before. There's been a lot o bruh ha ha over the years about which focus chart is best. I've used Yvon's printable focus chart successfully but also like this one amazon.com: DSLRKIT Lens Focus Calibration Tool Alignment Ruler Folding Card(pack of 2): Camera & Photo?tag=pentaxforums-20& For $5, you get two, and it's pretty easy to use. Like most inexpensive charts, isn't exactly one size fits all but works well enough for my needs. If you're really serious about lens calibrations and don't mind spending a few more bucks (okay a lot more bucks but you do get what you pay for), you can't beat the DataColor Spyderlenscal chart (this is closer to one size fits all) amazon.com : Datacolor SpyderLensCal SLC100 : Photographic Light Meter Color Calibration Charts : Camera & Photo?tag=pentaxforums-20& The sky's the limit, and I'm sure others can offer up solutions from their own experiences.

beholder3 · 08-21-2018, 12:26 AM - **1 Like**

Originally posted by jcleary47

Is it me? Is it an issue with my camera? I'm fairly new to shooting things that move, so maybe it's something I'm doing.

Some short extra comments:

AF detection needs contrast edges. Look at a childs face. Everything is round and smooth. The only real thing there are the eyes themselves. Your manual tracking of the eyes is important.
AF detection works if the AF point is very consistently over the exact same spot of the subjects. Again: practice, practice, practise keeping the AF point over the same contrast edge.
Older screwdrive lenses are notoriously poor at making fast and correct adjustments for erratic movements of the subject. Try a modern lens with AF motor in it.

MrB1 · 08-21-2018, 01:29 AM - **1 Like**

This is a question for the experts here rather than a suggestion:
Is it possible that, with both a moving subject and a moving camera, the SR might be working against the aim of getting a sharp image? Would it be better to switch SR off and set the exposure parameters to give a fast shutter speed to freeze all motion?

Philip

CarlJF · 08-21-2018, 05:44 AM

Originally posted by MrB1

This is a question for the experts here rather than a suggestion:
Is it possible that, with both a moving subject and a moving camera, the SR might be working against the aim of getting a sharp image? Would it be better to switch SR off and set the exposure parameters to give a fast shutter speed to freeze all motion?

Actually, yes it could be. But this will not make the focus appear at the wrong place. It will just makes the whole image softer, with focus made on the intended target.

beholder3 · 08-21-2018, 08:05 AM - **1 Like**

Originally posted by MrB1

to freeze all motion?

For most cases a shutter speed fo 1/125 sec is good enough for any normal human portraiture and corresponding focal lengths.

For erratic subjects turning SR off is a good idea - but in this thread's case this doesnt seem to be the issue.

jcleary47 · 08-21-2018, 05:14 PM

I borrowed a Spyder LensCal from a buddy of mine and have been taking a look with it. With my 77mm, I absolutely cannot discern much of a difference at all in focus point at the recommended 50x the focal length. I found another guide online that said to use 10x the focal length, and at that distance I can definitely see that I had to make an adjustment on my lens.

Is there any definitive stance on what distance I'm supposed to be from this thing?

Edit: attached image is taken at 7 feet with my 77mm set at 0 AF correction.

**alfa75ts** · 08-22-2018, 12:03 AM

Originally posted by jcleary47

Is there any definitive stance on what distance I'm supposed to be from this thing?

Close enough that the DoF fits within the scale. Somewhere around 1-1 on the scale would be nice but 5-5 would do unless B/F focus takes one end off the scale.

jawsy · 08-22-2018, 02:12 AM - **1 Like**

Originally posted by jcleary47

Is there any definitive stance on what distance I'm supposed to be from this thing?

I've always used 20x. Read it somewhere years ago and works pretty well.

(I use a metal chess board standing up with a steel ruler clamped to the side, so my target is a little bit bigger than most.)

**Rondec** · 08-22-2018, 02:51 AM - **1 Like**

For focus adjustment, I have typically used the live view feature of SLRs in this manner: Camera AF Microadjustment - for free Canon, Nikon, Sony - any camera with adjustment .

I will say that my experience AF-C is not nearly as good as with AF-S and with a child that is a little more fixed as yours was there, I would use AF-S. AF-C does work, but I find that with screw driven lenses the adjustments it makes are sometimes off just a bit -- enough to give some softness in the overall image. The others are right that stopping down a bit will help with sharpness too -- it just gives you more wiggle room with depth of field.

08-21-2018, 12:26 AM - 1 Like	#17
beholder3 Pentaxian Join Date: Dec 2011 Posts: 3,112	Originally posted by jcleary47 Is it me? Is it an issue with my camera? I'm fairly new to shooting things that move, so maybe it's something I'm doing. Some short extra comments: AF detection needs contrast edges. Look at a childs face. Everything is round and smooth. The only real thing there are the eyes themselves. Your manual tracking of the eyes is important. AF detection works if the AF point is very consistently over the exact same spot of the subjects. Again: practice, practice, practise keeping the AF point over the same contrast edge. Older screwdrive lenses are notoriously poor at making fast and correct adjustments for erratic movements of the subject. Try a modern lens with AF motor in it.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K1 Autofocus Behaviour : Autofocus lock	matroxication	Pentax K-1 & K-1 II	5	07-11-2018 07:15 AM
Not one, not two, not three, not four, but a wedding where half attendees are bob.	LeDave	Photographic Industry and Professionals	12	05-16-2016 03:40 AM
Kansas Rep. Pete DeGraaf: Getting pregnant from rape is just like getting a flat tire	deadwolfbones	General Talk	15	06-02-2011 09:15 AM
Help! Autofocus switch stuck on AF.S and will not autofocus!	pauldiebel	Pentax DSLR Discussion	3	09-19-2009 08:59 PM
For Sale - Sold: FS: Autofocus film cameras and autofocus lenses	Not Registered	Sold Items	15	03-17-2008 07:08 AM

08-20-2018, 08:30 PM	#16
david94903 Loyal Site Supporter Join Date: Nov 2010 Location: San Rafael, CA Photos: Gallery \| Albums Posts: 806	Originally posted by Wingincamera There are various ways to check & adjust the fine focus adjustment of your lens. I stumbled upon the DotTune method and find it really easy. dot-tune method - Bing video That's an interesting method, had not see that before. There's been a lot o bruh ha ha over the years about which focus chart is best. I've used Yvon's printable focus chart successfully but also like this one amazon.com: DSLRKIT Lens Focus Calibration Tool Alignment Ruler Folding Card(pack of 2): Camera & Photo?tag=pentaxforums-20& For $5, you get two, and it's pretty easy to use. Like most inexpensive charts, isn't exactly one size fits all but works well enough for my needs. If you're really serious about lens calibrations and don't mind spending a few more bucks (okay a lot more bucks but you do get what you pay for), you can't beat the DataColor Spyderlenscal chart (this is closer to one size fits all) amazon.com : Datacolor SpyderLensCal SLC100 : Photographic Light Meter Color Calibration Charts : Camera & Photo?tag=pentaxforums-20& The sky's the limit, and I'm sure others can offer up solutions from their own experiences.

08-21-2018, 01:29 AM - 1 Like	#18
MrB1 Pentaxian Join Date: May 2013 Location: Hertfordshire, England Posts: 845	This is a question for the experts here rather than a suggestion: Is it possible that, with both a moving subject and a moving camera, the SR might be working against the aim of getting a sharp image? Would it be better to switch SR off and set the exposure parameters to give a fast shutter speed to freeze all motion? Philip

08-21-2018, 05:44 AM	#19
CarlJF Veteran Member Join Date: Sep 2014 Location: Quebec City Posts: 1,185	Originally posted by MrB1 This is a question for the experts here rather than a suggestion: Is it possible that, with both a moving subject and a moving camera, the SR might be working against the aim of getting a sharp image? Would it be better to switch SR off and set the exposure parameters to give a fast shutter speed to freeze all motion? Actually, yes it could be. But this will not make the focus appear at the wrong place. It will just makes the whole image softer, with focus made on the intended target.

08-21-2018, 08:05 AM - 1 Like	#20
beholder3 Pentaxian Join Date: Dec 2011 Posts: 3,112	Originally posted by MrB1 to freeze all motion? For most cases a shutter speed fo 1/125 sec is good enough for any normal human portraiture and corresponding focal lengths. For erratic subjects turning SR off is a good idea - but in this thread's case this doesnt seem to be the issue.

08-22-2018, 12:03 AM	#22
alfa75ts Loyal Site Supporter Join Date: Jun 2009 Location: Melbourne Australia Photos: Albums Posts: 1,356	Originally posted by jcleary47 Is there any definitive stance on what distance I'm supposed to be from this thing? Close enough that the DoF fits within the scale. Somewhere around 1-1 on the scale would be nice but 5-5 would do unless B/F focus takes one end off the scale.

08-22-2018, 02:12 AM - 1 Like	#23
jawsy Veteran Member Join Date: Mar 2009 Location: Australia Photos: Gallery \| Albums Posts: 422	Originally posted by jcleary47 Is there any definitive stance on what distance I'm supposed to be from this thing? I've always used 20x. Read it somewhere years ago and works pretty well. (I use a metal chess board standing up with a steel ruler clamped to the side, so my target is a little bit bigger than most.)

08-22-2018, 02:51 AM - 1 Like	#24
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,652	For focus adjustment, I have typically used the live view feature of SLRs in this manner: Camera AF Microadjustment - for free Canon, Nikon, Sony - any camera with adjustment . I will say that my experience AF-C is not nearly as good as with AF-S and with a child that is a little more fixed as yours was there, I would use AF-S. AF-C does work, but I find that with screw driven lenses the adjustments it makes are sometimes off just a bit -- enough to give some softness in the overall image. The others are right that stopping down a bit will help with sharpness too -- it just gives you more wiggle room with depth of field.