SL2 - Intelligent AF anomoly

[chris_tribble]

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Has anyone else noticed an issue when using AF with the SL2?

CONTEXT - I'm working with VE 24-90 and VE 90-200 on the SL2. The same problem occurs with the Sigma 45 DG DN - so it's not a Leica lens specific problem. I usually default to field metering and AFS.  However, I've recently set Intelligent AF as a default. At the moment (lockdown!) I'm mainly working with landscape photography while doing socially distanced treks in the area around where I live.

ISSUE - I've started noticing that with Intelligent AF + Field (or ANY other relevant AF mode) the focus locks as normal on the selected area, but with the shutter half down to lock AF, the image in the screen blurs slightly.  The moment the shutter is fired (or pressure is released) everything snaps back into clarity.  I found this very distracting.  I think I've found the solution for now is to switch to AFS, where this behaviour does not manifest itself.  

REQUEST - Does any one else share this experience - or can you reproduce it?  If yes, any thoughts on a solution - or is this maybe a firmware issue we need to raise with Leica?  I'd be interested to hear your thoughts.

[Photoworks]

It is a normal behavior 

In fort you can see it in other brands too. I think it has something to do with EVF refresh rate. I see it it even worse in other cameras adding incredible amount of grain, probably from the  f-stop closing and letting less light true, to compensate there is an ISO boost for the preview.

I have also notice an incredible back and forth movement in AF-c that make it hard to compose and follow the subject expressions.

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[chris_tribble]

Ah! I never use AF-C so hasn’t noticed that issue - and I’m surprised that “intelligent” mode is a bit stupid 🙃

ah well. At least AF-S works really well for me.  

Thanks

[SrMi]

The observed resolution change in EVF is typical behavior in many mirrorless cameras. The camera reduces EVF resolution while focusing. With AF-S, the EVF blurs briefly while the camera acquires focus. With AF-C, the EVF blurs (reduces resolution) while focusing is active (e.g., half-press of the shutter button). I assume i-AF uses AF-C.

[chris_tribble]

Another lucid explanation. Thanks. What I useful place the forum can be. 
🙂

[sillbeers15]

When intelligent AF is chosen, you allow the camera to decide on AFS or AFC. If you work do not require you to do continuous focusing on multiple frames shooting over moving subject, it would be more stable to select AFS.

I’m not bothered by what I see in the EVF when trying to capture moving subjects, there are more challenges to occupy my priorities on getting a good shot over the short spans of time. It only matters to me on getting the AFC to work determined by final results.

[Slender]

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Yes, the blurring when using AFC or when iAF decides to do so is a bit disconcerting at first, but in action scenarios it is hardly a bother and the benefits outweight it. If you shoot landscape and people hiking - that is slow paced - stay in field and AFS. It does well even for street photography in my experience.

[Photoworks]

the biggest challenge is when a model walks to you and you walk back and keep the same distance.  AF goes real crazy, it is hard to see a clear view if you shoot continuously 

[FlashGordonPhotography]

The blur in iAF isn't EVF resolution! It's the DFD system cutting in.

Gordon

[SrMi]

37 minutes ago, FlashGordonPhotography said:

The blur in iAF isn't EVF resolution! It's the DFD system cutting in.

Gordon

What do you mean by "DFD system cutting in"? Do you mean that the perceived blur is caused by rapid lens movement?

[FlashGordonPhotography]

5 hours ago, SrMi said:

What do you mean by "DFD system cutting in"? Do you mean that the perceived blur is caused by rapid lens movement?

Yep. Basically. In iAf or AFC Leica's implementation of Panasonics DFD focus technology rapidly focus and defocuses to try and detect subject movement and movement direction. Basically the image is going in and out of focus extremely rapidly as the camera looks for subject movement. That's why it occurs in iAF and AFC but not AFS when looking through the viewfinder.

Got nothing to do with viewfinder resolution.

Gordon

[chris_tribble]

Even more helpful as an explanation. I keep on finding features of the camera I missed in the first phase of use. A case in point is the manual focus over-ride when in AF mode and the shutter release is half depressed. I’d not noticed that in the manual and since I’ve discovered this functionality on the Forum my use of the SK2 has been greatly enhanced. Thanks to all constructive, practical, generous photographers who comment and advise here. 👏

Edited January 27, 2021 by chris_tribble

[sillbeers15]

14 hours ago, FlashGordonPhotography said:

The blur in iAF isn't EVF resolution! It's the DFD system cutting in.

Gordon

I’m do not think it is caused by DFD as the function of DFD is for the camera processor to compare the subject focus via contrast against data base images for focusing mechanism to decide which direction to move and by how much (alternative to Phase Detect function in other non Panasonic AF system). The flickering & bluring seem to take place on the fine focusing phase. It definitely has to do with the algorithm that dictates the resolution changes in the EVF for some logic related to processing power allocation.

[FlashGordonPhotography]

9 hours ago, sillbeers15 said:

I’m do not think it is caused by DFD as the function of DFD is for the camera processor to compare the subject focus via contrast against data base images for focusing mechanism to decide which direction to move and by how much (alternative to Phase Detect function in other non Panasonic AF system). The flickering & bluring seem to take place on the fine focusing phase. It definitely has to do with the algorithm that dictates the resolution changes in the EVF for some logic related to processing power allocation.

Believe what you want. I'm not trying to convince you. It's been discussed here several times.

Gordon

[Simone_DF]

23 hours ago, sillbeers15 said:

I’m do not think it is caused by DFD as the function of DFD is for the camera processor to compare the subject focus via contrast against data base images for focusing mechanism to decide which direction to move and by how much (alternative to Phase Detect function in other non Panasonic AF system). The flickering & bluring seem to take place on the fine focusing phase. It definitely has to do with the algorithm that dictates the resolution changes in the EVF for some logic related to processing power allocation.

It happens on the Panasonics too, and with the recent firmware update the issue is still present but less visible, so yes, it's caused by DFD.

[Rob L]

On 1/26/2021 at 8:04 PM, FlashGordonPhotography said:

Yep. Basically. In iAf or AFC Leica's implementation of Panasonics DFD focus technology rapidly focus and defocuses to try and detect subject movement and movement direction. Basically the image is going in and out of focus extremely rapidly as the camera looks for subject movement. That's why it occurs in iAF and AFC but not AFS when looking through the viewfinder.

Got nothing to do with viewfinder resolution.

Gordon

Yes, you can even hear it! As discussed in one of those threads about the Summicron 35 recently.

[sillbeers15]

On 1/28/2021 at 5:17 AM, FlashGordonPhotography said:

Believe what you want. I'm not trying to convince you. It's been discussed here several times.

Gordon

I’m not believing on what I hear or read but based on logical analysis of algorithm control & functions. It is plain elementary physics and math.

[frame-it]

On 1/27/2021 at 12:04 PM, FlashGordonPhotography said:

Yep. Basically. In iAf or AFC Leica's implementation of Panasonics DFD focus technology rapidly focus and defocuses to try and detect subject movement and movement direction. Basically the image is going in and out of focus extremely rapidly as the camera looks for subject movement. That's why it occurs in iAF and AFC but not AFS when looking through the viewfinder.

Got nothing to do with viewfinder resolution.

Gordon

yes Correct

>>

"The problem with a regular contrast detection system, and unlike a phase detection focusing system, is that it has no idea which way the focus needs to be adjusted to get the subject sharp. This means that it has to hunt, adjusting the focus backwards and forwards to assess the impact on contrast at a pixel level. It also doesn’t know when to stop which means the focusing overshoots, going beyond the point of focus so it has to adjust back again. These tiny adjustments can go unnoticed in good light, but it slows focusing. In low light levels the backwards and forwards adjustment is often more visible.

It works by examining two images taken with the focus at different distances and analysing their sharpness so that the camera can determine which way and how far to adjust the lens to get the subject sharp. It all happens very quickly so you’re not aware of anything going on.

In order for DFD technology to work the camera needs to know the level of micro contrast that a lens can achieve and understand its bokeh, the quality of the out of focus areas. For this reason DFD focusing is only compatible with Panasonic’s lenses.

Although Panasonic’s DFD-enabled cameras have a database of information about the lenses that were current at the time of the body’s production, new lenses have the data stored inside them so that they can be used with existing DFD-capable camera bodies."

 

 

Edited February 1, 2021 by frame-it

[sillbeers15]

On 2/2/2021 at 7:55 AM, frame-it said:

yes Correct

>>

"The problem with a regular contrast detection system, and unlike a phase detection focusing system, is that it has no idea which way the focus needs to be adjusted to get the subject sharp. This means that it has to hunt, adjusting the focus backwards and forwards to assess the impact on contrast at a pixel level. It also doesn’t know when to stop which means the focusing overshoots, going beyond the point of focus so it has to adjust back again. These tiny adjustments can go unnoticed in good light, but it slows focusing. In low light levels the backwards and forwards adjustment is often more visible.

It works by examining two images taken with the focus at different distances and analysing their sharpness so that the camera can determine which way and how far to adjust the lens to get the subject sharp. It all happens very quickly so you’re not aware of anything going on.

In order for DFD technology to work the camera needs to know the level of micro contrast that a lens can achieve and understand its bokeh, the quality of the out of focus areas. For this reason DFD focusing is only compatible with Panasonic’s lenses.

Although Panasonic’s DFD-enabled cameras have a database of information about the lenses that were current at the time of the body’s production, new lenses have the data stored inside them so that they can be used with existing DFD-capable camera bodies."

 

 

Thank you for posting the DFD explanation. Without it, there is focus hunting and it slows down the focusing time. 
In a mirrorless camera, Phase detect system (it is actually a hybrid of Phase detect to move the focusing to the focus plane desired. However due to the lack of accuracy, the contrast detection actually takes over to finalise the focusing). 
so as the DFD write out explains, the normal contrast detection will take an unacceptable long time ( which occasionally still happens in low light situation where ‘focus hunting’ happens). All DFD provide is the direction & how much to focus for the initial focusing that replaces the Phase detection function.

The complaint of the focusing box flitters only in AFC mode happens when the refresh rate of the EVF shows the continuous focusing taking place on final focusing ( DFD comes into function when the initial focus travel distance is significant and requires a direction & distance to tell the lens to focus such that there is no focus hunting). Somehow the way the logic of the algorithm makes the EVF focusing box seem to be blur or out of focus relating to fine focusing of contrast detect but does not affect the image captured. When the EVF shows the blur or flittering effect, it happens without DFD function as the initial focusing has already taken place. All that can be showing is fine focusing taking place. DFD takes away the need to focus hunting and it does not cause focus hunting, so the EVF view finder blur or flittering has nothing to do with DFD.

If you guys think it has to do with DFD technology, why does it not happen to AFS mode (which employs DFD as well)?

 

Edited February 3, 2021 by sillbeers15

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[SrMi]

3 hours ago, sillbeers15 said:

Thank you for posting the DFD explanation. Without it, there is focus hunting and it slows down the focusing time. 
In a mirrorless camera, Phase detect system (it is actually a hybrid of Phase detect to move the focusing to the focus plane desired. However due to the lack of accuracy, the contrast detection actually takes over to finalise the focusing). 
so as the DFD write out explains, the normal contrast detection will take an unacceptable long time ( which occasionally still happens in low light situation where ‘focus hunting’ happens). All DFD provide is the direction & how much to focus for the initial focusing that replaces the Phase detection function.

The complaint of the focusing box flitters only in AFC mode happens when the refresh rate of the EVF shows the continuous focusing taking place on final focusing ( DFD comes into function when the initial focus travel distance is significant and requires a direction & distance to tell the lens to focus such that there is no focus hunting). Somehow the way the logic of the algorithm makes the EVF focusing box seem to be blur or out of focus relating to fine focusing of contrast detect but does not affect the image captured. When the EVF shows the blur or flittering effect, it happens without DFD function as the initial focusing has already taken place. All that can be showing is fine focusing taking place. DFD takes away the need to focus hunting and it does not cause focus hunting, so the EVF view finder blur or flittering has nothing to do with DFD.

If you guys think it has to do with DFD technology, why does it not happen to AFS mode (which employs DFD as well)?

 

It happens with AF-S as well, but just briefly. With AF-S focusing stops once it was acquired, hence only a brief "blur". With AF-C, focusing does not stop, hence continuous "blur".