S3 AF System...PDAF ?

[glenerrolrd]

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Does anyone know if the S3 AF system is PDAF or CDAF .  I understand from several reviews that the “focus post” can be moved around the frame .  This should help but the system in the S 007 is not IMHO adequate for the S3 .   I have read conflicting specifications and can not find any solid information on the new S3 AF .  You can t just point me to an existing review as I have seen it both ways .  

[davidmknoble]

Good quesiton @glenerrolrd, I’m sure this doesn’t answer your question, but for information, the S3 Spec sheet says “Predictive TTL autofocus with central cross sensor and phase detection.”

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[davidmknoble]

Also, in this post a few have talked about focusing:  old method mirror down (optical focusing) and newer technology mirror up (Live view through sensor).  I believe some of the older Nikon’s even used a mirror that was semi transparent to allow the sensor to perform some focusing, but have not seen specifics regarding the S3.

 

[glenerrolrd]

Yes       Very confusing explanations .  I am no expert but my limited understanding has been that :

             Only a PDAF based auto focus system can do focus tracking at a level required for sports . 

            A PDAF system requires on sensor hardware that can causes banding in high ISO captures .  

Those are gross generalizations and how there are differences in how well the designer implemented the technology .  

[tom0511]

I am pretty sure it is pdaf like previous models and contrast AF if you work in liveview-mode (on the display/without viewfinder).

 

[BernardC]

It seems to be the same basic design as the S-007. That's not to say that the implementation details haven't changed, but the overall idea is the same.

There's a phase-detection sensor at the bottom of the mirror box. That's the same system that every AF SLR has used since the Minolta Maxxum (a system originally invented by Leica). Phase-detect sensors, in a simplified explanation, are two sensors, one focused slightly in front of the image plane, and one slightly behind. The camera looks at the phase difference between the two, and focuses toward the one that is less sharp. It stops focusing when both images are equally sharp. That's what makes it fast, it knows which direction to focus the lens, and it stops when adequate sharpness is achieved. There are a few problems with this approach: it can only focus on one point per sensor, and it is limited in how finely it focuses. In a general way, sensors can be either good at smaller (darker) apertures, or accurate, but not both.

When in live-view mode, focus is determined by maximum sharpness/contrast on the sensor. That's essentially the same way you would do it on a view camera with a magnifier. This system is slower, but more accurate. It can also be used at any point in the image.

Some sensors have phase-detect elements on board, so they work in live-view. There is no indication that the S3's sensor is of this type. The same caveats apply: limited (though larger) number of focus points, limited accuracy. In addition, the phase-detect elements create "gaps" in the image which need to be filled-in, and they create more heat, which can limit DR. Some users also report banding issues with PDAF sensors.

Many newer cameras use a hybrid system in live view: they use phase-detect to get "almost focus," and then switch to contrast detect (provided they have the time). Panasonic's DFD system (used in SL, S1, S1R, SL2) uses complex lens mapping to achieve a kind of pseudo-phase-detect. It guesses which way to focus based on known characteristics of the lens.

 

The big picture, which people seem to be missed in these discussions, is that AF system always find something to focus, but they don't know what should be in focus, in order to convey the intended emotional message. That's the photographer's job.

 

I use my own hybrid system with the S: I push on the rear focus button when I need to make a big correction (from near to far, for instance), and then I fine-focus by eye. Tiny changes in focus make big differences in the impact of a photograph, and the odds of a camera and myself being on the same wavelength (wavefront?) are minimal. Often I will take two pictures in quick succession , using different focus points, because they convey completely different emotions.

 

I know that we would all love a "brain-detect" AF system, that reads our minds. That's not on the menu yet!

[davidmknoble]

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7 minutes ago, BernardC said:

I use my own hybrid system with the S: I push on the rear focus button when I need to make a big correction (from near to far, for instance), and then I fine-focus by eye. Tiny changes in focus make big differences in the impact of a photograph, and the odds of a camera and myself being on the same wavelength (wavefront?) are minimal. Often I will take two pictures in quick succession , using different focus points, because they convey completely different emotions.

@BernardC that was a great, easy to understand explanation.  Thanks! After reading that, I find it interesting to compare how I have always used manual focus SLR lenses (S007, R9, Nikon F2) to focus near and far through the focus plane I want, so that I can tweak it back and forth until the viewfinder seems to show it the sharpest.  Of course it's different with every lens because the base aperture is different and lets in different amounts of light to see and focus (f/1.4, f/2, f/2.8).  Since I wear glasses, I've always relied on diopter adjustments so I can shoot without glasses, but that introduces yet another variable.  

What complicates this is that the SL, SL2 seem to have such great focus systems, but they are 100% EVF and no optical VF, which is an incredible experience on the S. I do not shoot fast moving people or objects with the S, so for me, the focusing works well.  I could see how other uses might have limitations.  I'm a fan of the rear focus button to get me started and manual after that if needed. 

Not to be off topic, but I also prefer the non-micro prism focusing screens, because the cross in the center is easy to use as a point to focus with the AF system.  It may be harder to focus ultimately and if I had my choice, I would love to have a full microprism screen and a full matte screen for manual focusing, similar to the Nikon focusing screen choices  I find the small circles are not large enough for my eyes to quickly find the focus, but a full screen let's me compare more quickly and find the sharpest points.

Thanks again for an understandable explanation on the AF system!

[glenerrolrd]

Thanks good explanation .  Unfortunately the AF system in the S 007 misses all the important evaluation criteria .

 It is not precise ..agree best practice is AF to get close and fine tune manually . 

It will not track a moving object .  This can be disputed but I would ask exactly what type of moving object is being tracked .  

In fact without decent eye sight not sure how exactly you would use an S3 ( I have excellent eye sight so fine tuning manually is not an issue for me ..its just not as fast as I would like ). (Could be but I don t practice enough !).  

I could provide dozens of examples from my own work where a more capable AF system would be appreciated and far surpass ....AF to get close and manual fine tuning .  My primary system is the Leica M ..I use the SL2 and S007 ..but I also have a Nikon D5 for comparison ...so I know the differences in practical applications .    

 

 

 

 

[glenerrolrd]

Here is a good test and practical application . 

Take a model or willing subject and do some head and shoulder but also some full length captures .  Have the model move (like a fashion shoot) .  Shoot wide open or maybe at F 2.8 now check the leading eye .  Try purely manual focus ..then  spot AF and then spot with tracking .   

I did this last year with the Leica SL using one body with the 75 AF and another with the 50/1.4 R .  Then I did it a 2nd time with the 50/1.4 SL lens .  Technique is different with a manual focus lens and you have to think about your focus point and manage movement based on experience ....find the pause points and pre focus .  (use magnified view to get a precise eye lash ) etc . The AF lenses required a different technique ...predefine where the eye  would be in the frame (composition ) and then frame and spot focus on the eye for ever frame using the back button .  The SL is both fast and precise ..still way behind the more modern eye detect AF ..but close enough for my usage .  Again with practice . 

A weak AF system relies more heavily on the skill and technique of the photographer .  If you don t shoot your Leica S frequently its difficult to maintain the skill necessary for a decent hit rate . 

At a minimum the S3 should have fast and precise AF ...

 

[tom0511]

AF has been - IMO the biggest downside of the S-system. I think the AF-area is too big and sometimes picks a point slightly behind or in front of the cross/circle in the viewfinder. For example spot focus with the SL(2) is more precise. And even manual focusing is easier with EVF.

I hope the S3 has improved the AF acurancy.

 

 

 

 

[xiaubauu2009]

I thought all S camera has PDAF. Wonder whether this new S3 has a faster focus logic. Maybe not such a good idea as the motor even though upgrades might not be able to handle the faster AF speed. Hahah. 

Edited March 8, 2020 by xiaubauu2009

[albireo_double]

23 hours ago, tom0511 said:

AF has been - IMO the biggest downside of the S-system. I think the AF-area is too big and sometimes picks a point slightly behind or in front of the cross/circle in the viewfinder. For example spot focus with the SL(2) is more precise. And even manual focusing is easier with EVF.

I hope the S3 has improved the AF acurancy.

 

 

 

 

A lot of comments on the AF area being too big and the AF being unreliable in low light, to the point of becoming an "issue" for the S3 beta testers. OK, the AF of the S007 (which is the same as the S3) is kind of "antediluvian" but it is accurate and workable. I don't understand what people do to make the AF area to pick a point "slightly behind or in front" because it has never been my issue with the S2 and the S007, in the past eight years or so. Yes, the focusing mark is quite large but the viewfinder screen is accurate enough for me to see what is in focus and what is not. With a little use of my brain, I am usually able to pick an area that is the same distance as to where I want my focus to be. Ok, forget fast moving pets and toddlers, but I still fail to understand what this focus issue is all about. The biggest issue by far is the price. I am prepared to pay Leica Eur10k and surrender my S007 but if it is any more than that, then I pass. 

[davidmknoble]

3 hours ago, albireo_double said:

A lot of comments on the AF area being too big and the AF being unreliable in low light, to the point of becoming an "issue" for the S3 beta testers. OK, the AF of the S007 (which is the same as the S3) is kind of "antediluvian" but it is accurate and workable. I don't understand what people do to make the AF area to pick a point "slightly behind or in front" because it has never been my issue with the S2 and the S007, in the past eight years or so. Yes, the focusing mark is quite large but the viewfinder screen is accurate enough for me to see what is in focus and what is not. With a little use of my brain, I am usually able to pick an area that is the same distance as to where I want my focus to be. Ok, forget fast moving pets and toddlers, but I still fail to understand what this focus issue is all about. The biggest issue by far is the price. I am prepared to pay Leica Eur10k and surrender my S007 but if it is any more than that, then I pass. 

@albireo_double, I have had very few issues with focus, but even focusing on stationary people and animals have had some issues.  I use the standard screen with the circle and cross showing exactly what should focus.  My AF issues have mostly been with the APO 180mm and with smaller subjects on all the lenses wide open.  There are times were even using the back focus button and recomposing with a narrow depth of field just missing the focus.  On the other side, the SL, because it has an EVF, has a movable focus location, so it can be easy to compose, move the focus where you want, and then ensure it gets it just right.  

This is an issue with the optical viewfinder and getting the perfect spot with narrow depth of field.  Now, it could be my vision, because this also happens when I use f1/4 lenses on my Nikon F2 for film which also is an optical viewfinder.

In retrospect, I might almost rather have a focusing screen with a small square or circle for the focus point so it is easier to see the sweet spot and the split screen focusing screen is just not my favorite.

[glenerrolrd]

My ignorance took this thread off course .  The better question is does the S3 have an improved AF system .   As the MP in our cameras increase its easier to see even slight differences in focal point .  Anyone that shoots  portraits or fashion know that even slightly missing the focus on the eye ....results in a major loss in resolution and impact of the image .  

The S 007 AF system is simply inadequate reducing the range of subjects that the S can cover ..with a decent hit ratio . 

So the question should be ..is the S3 AF any different than the S 007 .  

 

[Flu]

1 hour ago, glenerrolrd said:

My ignorance took this thread off course .  The better question is does the S3 have an improved AF system .   As the MP in our cameras increase its easier to see even slight differences in focal point .  Anyone that shoots  portraits or fashion know that even slightly missing the focus on the eye ....results in a major loss in resolution and impact of the image .  

The S 007 AF system is simply inadequate reducing the range of subjects that the S can cover ..with a decent hit ratio . 

So the question should be ..is the S3 AF any different than the S 007 .  

 

I have a feeling that the S3 will unfortunately behave very similarly to the S 007 in regards to AF as well as many other functions. Why you ask? Because IMO the S3 is just a very slight evolution of the 007. The only significant upgrade I can see on paper is the MP count. It has the same exact body, the same exact processor, the same small sized low resolution back screen. Plus, it’s not even a touch screen. Same card slots, same top screen, same VF coverage, same AF module (although it’s claimed to be tweaked), same etc etc etc.

For situations where you have all the time in the world to fine tune focus, this cameras output is going to be amazing no doubt. The S 007 was already amazing in this regard. Leica promotional info states that it offers the S line of cameras as a “medium format system that is suppose to behave like a DSLR with it’s form factor and range of usage.” In other words, it’s suppose to replace a DSLR and be able to be used in any or at least most of the situations where a DSLR would normally be used. I have tried to do this with the S007 covering various social gatherings and events where moments are fleeting and are gone within a few seconds. My successful AF hit rate is roughly around 65-70% (outdoor with good light) with the 100 f2. Other lenses faired another 5-10% better. To wrap it up, I believe the S3 still to be a studio/landscape camera first and foremost and on paper, there doesn’t look to be enough revolutionary upgrades when compared to the 007 to warrant an upgrade.

Having said that, I do reserve the right to change my mind once I get a hands on with a test unit to either confirm or debunk my thoughts here. For the record, I do hope in this case that I am dead wrong!

[davidmknoble]

This would be a good thread to start again in about a month, when we have some users that have an S3 and have had time to try it out ....

[xiaubauu2009]

Being a Maestro II processor, the improvement towards AF will be limited. The speed and capacity of the processor pretty much will be the same, even with new algorithm, it wont be a huge difference as say switching from GFX50s to GFX100.

also, do Leica really want to make the AF speed more aggressive? the new fix to the AF motor might break again! 

[BernardC]

I am sure that the live-view AF speed will be improved, now that Leica has a lot of SL and SL2 experience.

They may have improved the speed or accuracy of the PDAF sensor used in SLR mode, but probably not both. Leica is limited by what sensors are available from suppliers, their volume is too small for a bespoke item.

[tom0511]

For me priority is accuracy over speed any day for a medium format camera. I never found the S too slow, but I sometimes struggle with accuracy.

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[albireo_double]

I should add to my earlier post that I usually take more than one image and refocus between each click. So yes, with the 100S in particular, I don't have a hit rate higher than say 70%, either, but that has not prevented me from getting acceptable results. It is a question of adjusting one's process to accommodate the specifics of the equipment, I guess. Within the medium format, I think the only system fast and accurate enough is the big 100MP Fuji, all other systems have some issues and necessitate workarounds (I have been shooting with a Phase One XF for a while, with a lot of back focus issues in practical use, no matter what lens, despite the system being accurate when tested with a Lens Align target...go figure).