SL2-s low light autofocus

[jiggyb21]

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Hi everyone. I am a longtime lurker of this wonderful forum but have never signed up until today. I have owned a Q2 for a couple of years now and recently purchased a used SL2-s. 
 

Basically I fell in love with my Q2 and just wanted something similar with interchangeable lenses. Along with the SL2-s, I purchased the Sigma 45mm 2.8 contemporary. 
 

That brings me to my autofocus question. Let me first say that I researched extensively before buying the SL2-s and the consensus seemed to be that the SL2-s’ autofocus system was very similar to the Q2, if not a touch better.  Basically, the autofocus was poor for video but, for photographers, just fine. I have photographed a few small events for friends using the Q2 so I was fairly confident I knew what to expect, which by and large was a good thing.
 

After a day of shooting the SL2-s outdoors I was very happy with the camera overall. I love using it. And the Sigma 45 was just what I was hoping for too. Last night I had a few friends over and was shooting in my lowly lit home. A few lamps on here and there, that type of thing.  The autofocus was downright abysmal. 

The first thing I tried was to change the size of the focusing patch. That didn’t change the performance. Secondly, I tried all the different focusing modes and oddly the face/eye mode worked the best, and I was not shooting people. I played around with all the autofocus parameters to no avail. I spent about an hour trying to improve the autofocus. 
 

Again, I understand the general limitations of contrast detect autofocus and I thought I had a handle on it. My two main cameras for years now have been a Canon R5 and a Fujifilm x70 and x100f. I went downstairs and grabbed the Fujis and they both acquired autofocus where the SL2-s would not. They are both contrast detect systems. 
 

The only conclusion I can drawn from alll this is that it is the Sigma 45mm lens that is struggling so much. I read and watched nothing short of 20 articles and video reviews of these Sigma lenses before settling and the consensus was overwhelming positive, even in the AF department. 
 

The reason I am reaching out after just one night is that I purchased both the camera and lens used from MPB. Both were “like new” and they certainly seemed like it. I put more wear in them in 24hrs than anyone did to that point so far.  The 45 is the only lens I have for the system so I have nothing to compare it to but can obviously return either one in the next couple of weeks. 
 

-Can anyone offer their thoughts?

-How do people feel the AF compares to the Q2 and Fuji x100F, in general.

-Does anyone have experience with these Sigma primes?

Thanks so much!

 

[xlh]

Hi and welcome. I have the same combination ( SL2-S & Sigma 45/2.8 ) as well as Leica primes and I have no problem acquiring focus in the same lighting conditions as you describe. Since you bought the SL2-S used you might want to check a few things to make sure the original owner didn't change certain settings.

- Is the auto focus assist lamp on when shooting low light subjects?

- Is image stabilization active?

- Are your shutter speed/ISO settings sufficient for low light ( are you not acquiring focus or is it camera shake ) ?

- Did the original owner set up custom profiles and perhaps you are using one of them that is not ideal for low light?

You might try a system re-set and start fresh from there.

I have never had any problems with the Sigma 45 focusing - even when shooting fireworks, street scenes at night etc.

Good luck!

[FrankX]

vor 5 Stunden schrieb jiggyb21:

Again, I understand the general limitations of contrast detect autofocus and I thought I had a handle on it. My two main cameras for years now have been a Canon R5 and a Fujifilm x70 and x100f. I went downstairs and grabbed the Fujis and they both acquired autofocus where the SL2-s would not. They are both contrast detect systems. 

First, just to clarify: To my best knowledge both Fuji cameras are using a hybrid contrast/phase AF system! That’s the main reason for their superior performance in dark environments.

Second, the Q2 lens and sensor are well optimized by Leica. The lens is probably also sharper and transfers a more contrasty image to the sensor. That may be the reasons why it works more reliable than the SL2-S with the Sigma.

Third, all my Sigma lenses are not the best regarding AF performance, especially in low light. LUMIX lenses are way better than Sigma lenses. My SL2 feels like a different camera using LUMIX lenses…

Thus, I don’t think there is something wrong with your equipment. 

Edited June 18, 2023 by FrankX

[jiggyb21]

Thank you both for your replies.  

 

@xlh I did indeed factory reset the camera immediately upon receipt.  Image stabilization was on.  I turned the autofocus lamp off.  I always do as the moments I am trying to capture are candid ones, usually ruined by a light.  But that is a good point and something I did not try in my hour or so of investigative work.  Thanks.  

 

@FrankX I looked in the manual for both the x70 and x100F and you are absolutely correct.  Both cameras have points in the center that are indeed phase detect.  I was completely wrong and still surprised to be honest.  I thought that technology didn't hit their smaller cameras until the newest x100V.  

 

I can rule out camera shake as the focus wouldn't actually ever lock on to anything.  It would hunt slowly from one extreme to the other and eventually fail and turn red, not green.  The autofocus in good light is almost as fast and confident as my R5 so I really can't imagine there's actually anything wrong with it fundamentally.  That's a great point about the fixed lens of the Q2 being optimized.  I'm sure they rang every bit of performance from that combination.  I am so happy with the camera and how I think it will help me make better photos that I will likely order a different lens very soon and hopefully that will help shed some more light on this.

Thanks again!

[LocalHero1953]

My own experience of the Q2 and SL2-S is that the AF of the latter is streets ahead of the Q2. Obviously my experience may be down to how I use them. I would like to use the Q2 in low light and Face Detect, but actual low-light colour and noise are not great, and I find Face Detect on the Q2 effectively unusable - it just can't find faces unless they in full view, face on, within a couple of metres at most. I use the SL2-S extensively for low light people photography (typically theatrical and musical rehearsals/performance), and I normally set it to iAF and Body/Face/Eye Detect. With the 24-90SL, 90-280SL, or Apo-Summicron-SL 75 and 90, the camera easily picks up faces at all normal distances and sizes within the frame. I'm told that the latest Sony A7 and high-end Canon R series are much better still, but I have no major grumbles about the SL2-S.

For the less common occasions when I don't use this AF set-up, I have found AFs single point/spot focus to be unreliable (it sometimes fails to find something to focus on), but zone and field focus are OK. I never use the focus-assist light, and I hardly ever use AFc. I find AF is almost always accurate; if there are problems they are in failing to find a focus at all. I use the Q2 almost always now with AFs and zone focus, and don't have too much trouble with it, for speed or accuracy - though, as I said, in good light.

You mention hunting slowly; this is not my experience with my Leica lenses. I wonder if the Sigma lens and AF system compatibility is the problem.

Edited June 18, 2023 by LocalHero1953

[Simone_DF]

In terms of autofocus, the Sigma 45 is the weakest of all Sigma’s offering, especially near mfd. 

[jiggyb21]

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3 hours ago, LocalHero1953 said:

My own experience of the Q2 and SL2-S is that the AF of the latter is streets ahead of the Q2...........

You mention hunting slowly; this is not my experience with my Leica lenses. I wonder if the Sigma lens and AF system compatibility is the problem.

Now we're talking! Thanks so much for the detailed reply, it's exactly what I was looking for.  The more I read and the more I have tested today, the more I believe it likely comes down to the 45mm Sigma.  More on the slow hunting; it is like nothing I have ever seen on a camera before.  Actually "hunting" isn't even the right word for it.  Even if I manually focus near to the right place and then flip the switch to AF and half press (or leave it in MF and engage back button focus on the joystick), the focus is instantly pulled to one extreme and then slowly and steadily transitions to the other extreme and back.  Along the way it passes sharp focus somewhere in the middle.  At the conclusion I get the red box for failed focus.  The other thing I haven't seen before is that in low light, the evf and the live view both show the ISO-boosted image clearly (and this is true with Extended Live View on or off) but once I engage focus and the camera begins to "hunt" the screens are almost completely dark.  Whether or not focus is found, the brighter image is restored afterward.  I am used to the ISO-boosted preview remaining displayed throughout the focusing process.  I guess when focusing it can't simultaneously display the ISO-boosted image on the displays.  

I just tested again in a dark room and found the camera to focus better with Extended Live View turned OFF which seems slightly counter intuitive to me.  Maybe the purpose of that feature is to allow better MF in dark situations.    

1 hour ago, Simone_DF said:

In terms of autofocus, the Sigma 45 is the weakest of all Sigma’s offering, especially near mfd. 

Honestly, I'll take that as good news.

Edited June 18, 2023 by jiggyb21

[Anakronox]

Don’t think anyone else has asked this: are you using AF-S or AF-C?  In my experience AF-C isn’t reliable at all but AF-S is quick and accurate in low light, especially with the recent firmware revisions.  May also want to check that as well. 

I keep the focus assist lamp on though with my SL2. 

[jiggyb21]

4 hours ago, Anakronox said:

Don’t think anyone else has asked this:

I am indeed using AF-S. 
 

This all makes me curious about which size focus point people are using if they are using field. I haven’t found much difference in performance between small, medium and large. 

Edited June 19, 2023 by jiggyb21

[Simone_DF]

There's a very long thread on this lens on the FM forum:

https://www.fredmiranda.com/forum/topic/1608234/