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**UncleVanya** · 12-28-2021, 09:53 PM

Originally posted by lotech

If the SFX knew the correct way to turn then wonder why not my K3 then.

I’m not claiming that… Lol. I suspect it’s the 55-300 that’s involved more than just the body. Different lenses focus at different speeds and ways. Confusing is what autofocus can be!

lotech · 12-28-2021, 10:35 PM

Originally posted by UncleVanya

I’m not claiming that… Lol. I suspect it’s the 55-300 that’s involved more than just the body. Different lenses focus at different speeds and ways. Confusing is what autofocus can be!

Not only the HD 50-300 but also the old version of it also act like that if I remember right, so does the 80-320 I still have now, I can't tell the 18-135 IF coz it IS IF !

Ian Stuart Forsyth · 12-28-2021, 10:59 PM

Originally posted by lotech

If the SFX knew the correct way to turn then wonder why not my K3 then.

The subject that you might have be trying to photograph could have had spurious detail that the AF system was trying to align to achieve focus.
This can happen with subjects with a repeating pattern, things like feathers, screen doors to ripples in water. while these patterns might fall out of focus their patterns can cause the sensor to think that 2 separate lines spaced apart are a single line and adjusts the focus so that they become one

Jonathan Mac · 12-29-2021, 01:19 AM - **1 Like**

Originally posted by lotech

If that's the case I wonder why my 50-300 always turn to the wrong and long way before turn back, old film camera may base on the split focusing screen to determine which way to go where on DSLR it's all clear screen, but I don't have a SFX to test.

The focusing screen has no impact on AF as it's not used by the AF system.

lotech · 12-29-2021, 02:45 AM

Originally posted by Jonathan Mac

The focusing screen has no impact on AF as it's not used by the AF system.

Does the K3 have a half mirror ?

**UncleVanya** · 12-29-2021, 06:49 AM

Originally posted by Jonathan Mac

The focusing screen has no impact on AF as it's not used by the AF system.

Excellent point.

lotech · 12-30-2021, 06:08 PM

I just watch a review of the PLM 55-300 it blows my mind it focuses so quick, I will get this lens someday and forget about the "which way to turn" focus problem ha ! just wonder if the K3MK1 support that with the last FW update ?

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12-28-2021, 09:53 PM	#31
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,464	Originally posted by lotech If the SFX knew the correct way to turn then wonder why not my K3 then. I’m not claiming that… Lol. I suspect it’s the 55-300 that’s involved more than just the body. Different lenses focus at different speeds and ways. Confusing is what autofocus can be!

12-28-2021, 10:35 PM	#32
lotech Pentaxian Join Date: Apr 2012 Posts: 1,312 Original Poster	Originally posted by UncleVanya I’m not claiming that… Lol. I suspect it’s the 55-300 that’s involved more than just the body. Different lenses focus at different speeds and ways. Confusing is what autofocus can be! Not only the HD 50-300 but also the old version of it also act like that if I remember right, so does the 80-320 I still have now, I can't tell the 18-135 IF coz it IS IF !

12-28-2021, 10:59 PM	#33
Ian Stuart Forsyth Pentaxian Join Date: May 2009 Location: Somewhere over the rainbow Photos: Gallery Posts: 1,531	Originally posted by lotech If the SFX knew the correct way to turn then wonder why not my K3 then. The subject that you might have be trying to photograph could have had spurious detail that the AF system was trying to align to achieve focus. This can happen with subjects with a repeating pattern, things like feathers, screen doors to ripples in water. while these patterns might fall out of focus their patterns can cause the sensor to think that 2 separate lines spaced apart are a single line and adjusts the focus so that they become one

12-29-2021, 01:19 AM - 1 Like	#34
Jonathan Mac Pentaxian Join Date: Apr 2009 Location: Madrid, Spain Posts: 10,911	Originally posted by lotech If that's the case I wonder why my 50-300 always turn to the wrong and long way before turn back, old film camera may base on the split focusing screen to determine which way to go where on DSLR it's all clear screen, but I don't have a SFX to test. The focusing screen has no impact on AF as it's not used by the AF system.

12-29-2021, 02:45 AM	#35
lotech Pentaxian Join Date: Apr 2012 Posts: 1,312 Original Poster	Originally posted by Jonathan Mac The focusing screen has no impact on AF as it's not used by the AF system. Does the K3 have a half mirror ?

12-29-2021, 06:49 AM	#36
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,464	Originally posted by Jonathan Mac The focusing screen has no impact on AF as it's not used by the AF system. Excellent point.

12-30-2021, 06:08 PM	#37
lotech Pentaxian Join Date: Apr 2012 Posts: 1,312 Original Poster	I just watch a review of the PLM 55-300 it blows my mind it focuses so quick, I will get this lens someday and forget about the "which way to turn" focus problem ha ! just wonder if the K3MK1 support that with the last FW update ?

How does AF decide which way to go

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