NX500 - Disappointed by AF performance

Clive99 wrote:

I always use AF selection..never let the camera decide. I use AF speed priority. I also half press first and wait for box to go green before full press.

Pretty much the same for me; I use Single AF so I can decide where the focus should be and with the 30mm for shots like the birthday party photo example set the aperture to smaller than f/2 - usually going with f/4 for more dof and faster focusing (I use Aperture mode with a minimum shutter speed set in menu and Auto ISO capped at 3200).

With some practice I have learned to find those higher contrast areas within my chosen dof, which will help the lens achieve faster focus. I also have the AEL lock button set to be used as an AFL Lock only button; for when I will be shooting several shots from the same distance.

With the NX500 versus the earlier NX cameras I have used, there is less concern for me about ISO getting higher.

face detect AF works good. Might be an option worth trying...

and use Direct manual focus when you find the AF hunting a lot in a special scene..

dont use CAF in such scenes.. its true Samsung doesnt explain that in their manuals, but i also find the CAF making a lot of problems in Lowlight.. i use an NX1 by the way... in low light CAF tends to focus hunt.. sometimes finds focus and then looses it again.. SAF is considerably better in low light.. i also do use Prefocus /locked focus.. i push the AF button on the back and when it has found AF i am set for waiting for the right expression of the subject..of course works best if people are not moving around...like people sitting at a table etc.

also take care how big your focus box is.. bigger box usually works better in lowlight, but you must be aware which contrast it finds.. AF certainly prefers hard contrast and especially vertical lines...
it doesnt like soft contrasts like you find in faces unfortunately.. 
personally i wish for an eye detect AF like Sony A7RII...

for some strange reason it works also better with AutoISO.. maybe the cam finds better contrasts when the scene is exactly as bright as it needs it..

I guess it's worth experimenting. I agree that more direct and precise control over the AF target is better than less. The only times I use CAF with many boxes is with fast moving subjects like running kids, otherwise uusually a single shot with one box for best precision.

Re. the smallest focus box, I found that it only works if there is sufficient contrast within that box. I tried the smallest AF box for a time with all sorts of lenses and situations, but have reverted back to standard size or just one size down for most shots. Experiment and see what works best for you.

Andrea

Yes, I have the same experience with the smallest focus box when in low light..sometimes I have to back off and go with the 2nd smallest to achieve focus.

I have compared the zone selection vs smallest focus box in an outdoor environment with kids on bikes.  Although the zone is much easier to do, if I pay close attention I do get better results with the smallest single point.  One thing that can help immensely is using a viewfinder of some sort - I use the Clear Viewer when I really need to nail focus.

BTW I too use Aperture priority with minimum shutter speed and auto ISO. It works so well that I find myself using this mode 90% of the time.

For what it's worth, I've spent a while trying to do action shots with both the Nikon 1 S1 and the NX500.  They both have their strengths and weaknesses. The Nikon is much better in low light and does not hunt, but it's focus box is much bigger and frequently focuses on the edge of the box.  I like the pinpoint accuracy of the small focus box in the NX500, but bad light conditions cause problems and it's not great with the 30mm. Nothing is perfect for focussing..except maybe my old heavy  D300:)

Clive

Thanks, Clive, also for your tip about the Clear Viewer. I shall check that one out!

I don't own Nikon's 1 system, so can't say anything about it, but thanks for telling us about the comparison. It's interesting to hear how different cams operate in difficult lighting. I think there is no AF perfection for mirrorless APS-C and smaller yet (Sony now claims low light AF perfection for its latest FF models, but they talk a lot when the day is long, as we say in German), so we have to work with it. Somehow. I hope that three years from now this last remaining problem will be a thing of the past.

Andrea

andre95 wrote:

Raw Jaw wrote:

Thank goodness it was the camera and not you.

No need to be offended?

I consider myself a beginner, and don't know the technical details. You suggested that using Continuous AF was the big mistake, and that I should read the handbook. The handbook did not clarify why Cont AF performs so much worse (this, BTW, is just speculation, we don't know whether single-AF would have been the solution, but of course I'll try).

So, all I did was ask, and I do it again: Can you explain to me why Cont AF performs so much worse?

I mean, some scenes didn't change much overall (like blowing out the candles), but still a lot happened. So I just took one picture after the other. Approx. 30% are utter rubbish, i.e. focussed on something completely different than the AF-square or is totally blurred (see the attached example, before releasing the shutter, there was a green square just covering the face of the central child). The next two images focussed on the red box in the background (at least something), and the next image was nicely focussed on the face of the girl (the way I wanted it, and the way I would have thought because indicated by the green square on the face).

Honestly, how can I avoid this? I take a series of pictures under virtually identical conditions, and some shots go wrong by so much?

If I can do better, then I really want to. But for this I need to understand what went wrong.

Best wishes,

Andre

You are shooting at F2 fairly close to the subject, which means your depth of field is pretty small. Also, the center of the image does not have much contrast, which is what the camera looks for. The subject is likely moving around, which makes it that much more difficult for the camera. All of those things combined spell trouble if you are shooting in low light with a lens that is a slow focuser.

Suggestions:

1) Choose something with high contrast to get the focus, then recompose and complete the shutter press.

2) Get in the habit of using DMF for those sorts of scenes. If I am shooting scenes with critical focus (I have an NX1, with the 16-50mm S and 50-150mm S lenses, so those might be quicker than your system) I use the autofocus to get the ball park range, then use DMF to adjust to get critical focus (you get focus magnification and peaking visible when you use DMF). Once you get used to doing it, you can do it in a fraction of a second, and it gives you much better focus consistency.

3) Use manual focus if the girls are sitting there for a while, and compose your field of focus beforehand. Again, once you get some practice doing this you can do it quite quickly.

andre95 wrote:

Raw Jaw wrote:

Thank goodness it was the camera and not you.

No need to be offended?

I consider myself a beginner, and don't know the technical details. You suggested that using Continuous AF was the big mistake, and that I should read the handbook. The handbook did not clarify why Cont AF performs so much worse (this, BTW, is just speculation, we don't know whether single-AF would have been the solution, but of course I'll try).

So, all I did was ask, and I do it again: Can you explain to me why Cont AF performs so much worse?

I mean, some scenes didn't change much overall (like blowing out the candles), but still a lot happened. So I just took one picture after the other. Approx. 30% are utter rubbish, i.e. focussed on something completely different than the AF-square or is totally blurred (see the attached example, before releasing the shutter, there was a green square just covering the face of the central child). The next two images focussed on the red box in the background (at least something), and the next image was nicely focussed on the face of the girl (the way I wanted it, and the way I would have thought because indicated by the green square on the face).

Honestly, how can I avoid this? I take a series of pictures under virtually identical conditions, and some shots go wrong by so much?

If I can do better, then I really want to. But for this I need to understand what went wrong.

Best wishes,

Andre

You are shooting at F2 fairly close to the subject, which means your depth of field is pretty small. Also, the center of the image does not have much contrast, which is what the camera looks for. The subject is likely moving around, which makes it that much more difficult for the camera. All of those things combined spell trouble if you are shooting in low light with a lens that is a slow focuser.

Suggestions:

1) Choose something with high contrast to get the focus, then recompose and complete the shutter press.

2) Get in the habit of using DMF for those sorts of scenes. If I am shooting scenes with critical focus (I have an NX1, with the 16-50mm S and 50-150mm S lenses, so those might be quicker than your system) I use the autofocus to get the ball park range, then use DMF to adjust to get critical focus (you get focus magnification and peaking visible when you use DMF). Once you get used to doing it, you can do it in a fraction of a second, and it gives you much better focus consistency.

3) Use manual focus if the girls are sitting there for a while, and compose your field of focus beforehand. Again, once you get some practice doing this you can do it quite quickly.

That helps me. Never considered using AF to get into the ball park range before switching to manual. Is there a fast way to switch between manual and auto focus? The 45 has a switch but other lenses I own don't so I have to hunt for it in the settings.

I'm not sure if it's a quirk of the 45mm or of my galaxy NX, but when I switch from AF to MF using the button the DMF gets disabled which means I then have to hunt for it in settings. This is quite annoying and doesn't happen with the 30mm.

I have one more Idea what could have contributed to the problem:

The 30mm does not have antishake.

If the camera is not hold quite steady, then the Focus has another area where it has to focus at each iteration.

And this combined with the old 30mm with slow focus motor.

Perhaps Focus would have been a bit better from a monopod or with a technique to hold the cam very steady.

Other problems of the AF have been mentioned above - this non-antishake problem may be one contributing factor to the problems

I just want to say Thanks! again, I really learned a lot. I'm still reading the new comments, but I'm very busy today and tomorrow, not sure whether I'll be able to further comment.

Cheers,

Andre

andre95 wrote:

Raw Jaw wrote:

Thank goodness it was the camera and not you.

No need to be offended?

I consider myself a beginner, and don't know the technical details. You suggested that using Continuous AF was the big mistake, and that I should read the handbook. The handbook did not clarify why Cont AF performs so much worse (this, BTW, is just speculation, we don't know whether single-AF would have been the solution, but of course I'll try).

So, all I did was ask, and I do it again: Can you explain to me why Cont AF performs so much worse?

I mean, some scenes didn't change much overall (like blowing out the candles), but still a lot happened. So I just took one picture after the other. Approx. 30% are utter rubbish, i.e. focussed on something completely different than the AF-square or is totally blurred (see the attached example, before releasing the shutter, there was a green square just covering the face of the central child). The next two images focussed on the red box in the background (at least something), and the next image was nicely focussed on the face of the girl (the way I wanted it, and the way I would have thought because indicated by the green square on the face).

Honestly, how can I avoid this? I take a series of pictures under virtually identical conditions, and some shots go wrong by so much?

If I can do better, then I really want to. But for this I need to understand what went wrong.

Best wishes,

Andre

Nothing is in focus with that shot. I am surprise the shutter even fired. So I am not sure what is happening there but at iso800, 1/250, f2, the lighting is not dark at all. I was shooting moving kids in and indoor playhouse inside a maze and I can get focus in very dark condition with the 16-50 pz. It can focus with iso5000, f3.5, 1/50 (but a bit of blur for the moving kid). I was quite impressed on fast the focus was (with latest firmware 1.11). I was using continue AF, multi-point focus. I imagine zone focus might be better your situation.

I am guess the shutter fired before acquiring focus. The 30mm pancake is not exact fast but your lighting condition is not exact dark, even for that lens.

andre95 wrote:

Thanks for all the helpful input, I'll try a lot of the suggestions you've

made.

Just to clarify a few things:

- "Cont normal" was the Drive mode, but the examples I have shown are single shots. They are not taken from a sequence of having pressed the shutter continuously. Press shutter, take 1 picture, release shutter. Wait briefly. Press shutter, take 1 pic, release, etc.

- I have set the AF to Selection AF. Mostly, I have the AF field pretty much in the middle. The size is the third-smallest. With smaller squares, I have athe situation of finding no focus even more often.

- I indeed may have often pressed the shutter fully in one go. However, in the German DSLR forum, a Canon guy with pretty much high-end equipment recently was wondering why his dog-shots were all not well focussed. They all recommended (and it turned that this was indeed the major problem), to press the shutter in one go, and *not* to press it halfway first. Kids are often moving at least a little bit, and with f2 this time delay may mean that e.g. the eyes are not in focus any more. I will experiment with it...

BTW, I shot true continuous shooting with the 50-200mm in a running game. AF and picture yield are fabulous (honestly, I'm still baffled).

Attached is another great example, this time outdoors. And no, I wasn't focussing on the finger The green square was roughly at the boxed out portion of the face (not my daughter, so anonymous). I know, it is backlit again, but still I find this poor...

Best wishes,

Andre

I would not shot a fast moving kid with the 30mm, but your photo the kid is not moving fast so I think it should be ok.

My choice of focus for that is continuous AF with multi-point AF, Tracking On, and Continuous Normal or High . Half press shutter button and you should see the dancing green square sticking to the kid, press all the way when ready to shot.

I guess it focused on the flame for some reason?