Nx1 issue for me

[mac west]

I started shooting a test subject after a recent post about back focusing. I Cant get a shot at 2.8 50mm in focus using my only lens 16-50 s . If I use manual focus it works fine . I am shooting on a tripod with image stabilization off and hand holding with it on and off at least 12 inches from subject. Anyone else notice this? Example focus on head. Turtle on right.

 

[chespirito]

I see it focusing, but not on the head.

 

[mac west]

And if I manual focus it with the center point smallest size focus point it will be perfect, But auto same settings out of focus. Mac

 

[ttbek]

I started shooting a test subject after a recent post about back focusing. I Cant get a shot at 2.8 50mm in focus using my only lens 16-50 s . If I use manual focus it works fine . I am shooting on a tripod with image stabilization off and hand holding with it on and off at least 12 inches from subject. Anyone else notice this? Example focus on head. Turtle on right.

Well, is it giving up its attempt to focus and still letting you shoot, or is it claiming it has found focus (and if so, did it claim it on the point that is in focus or in the area that is not)? I ask because frequently AF doesn't extend all the way to the minimum focusing distance so you have to use MF if you want to get focus that close. Does it also have problems at somewhat greater distances (e.g. 2 ft, anything significantly more than 1 ft)?

 

[ttbek]

And if I manual focus it with the center point smallest size focus point

Now you're confusing me, if you're using MF, then what does the size of the focus point have to do with anything?

it will be perfect, But auto same settings out of focus. Mac

 

[mac west]

it gives me focus confirmation . I made sure I was a foot away. I am going to try right now 2 feet. Mac

 

[mac west]

And if I manual focus it with the center point smallest size focus point

Now you're confusing me, if you're using MF, then what does the size of the focus point have to do with anything?

it will be perfect, But auto same settings out of focus. Mac

well that's what's lit up until I turn the lens. Mac

 

[mac west]

Focus is better at two foot. But I can focus it manually better then the camera can. I will stick with manual focus on close ups until a firmware update improves it . I am home with a injury and experimenting with my camera its no big deal I rarely shoot that close. Mac

 

[Kaziklu]

it gives me focus confirmation . I made sure I was a foot away. I am going to try right now 2 feet. Mac

Do you mean using Direct Manual Focus?



manual focus wouldn't have any focus points. Where as Direct Manual Focus lets you try to focus and then change the focus.. but not changes to the focus spot should occur.




In this case you are trying to focus on a point with a strong shadow with a heavy back light. The likely reason you are having an issue is the PDAF is able to focus in EV-2 heavy back light can confuse that though in many cameras particularly if you are using Multi metering. The Contrast Focus can focus in EV -3 or -4 (I believe it is -4) but this requires there to be contrasting elements. And the head is small and may not have enough contrasting elements for it to easily lock on to.



You may want to try to use Spot metering in this case and see if that helps any. Though honestly I really think that it is a combination of the head being at greater than EV -2 and not having enough contrast for the Contrast Focus to lock on to.

 

[mac west]

it gives me focus confirmation . I made sure I was a foot away. I am going to try right now 2 feet. Mac

Do you mean using Direct Manual Focus?

manual focus wouldn't have any focus points. Where as Direct Manual Focus lets you try to focus and then change the focus.. but not changes to the focus spot should occur.

In this case you are trying to focus on a point with a strong shadow with a heavy back light. The likely reason you are having an issue is the PDAF is able to focus in EV-2 heavy back light can confuse that though in many cameras particularly if you are using Multi metering. The Contrast Focus can focus in EV -3 or -4 (I believe it is -4) but this requires there to be contrasting elements. And the head is small and may not have enough contrasting elements for it to easily lock on to.

You may want to try to use Spot metering in this case and see if that helps any. Though honestly I really think that it is a combination of the head being at greater than EV -2 and not having enough contrast for the Contrast Focus to lock on to.

Good suggestion I will try spot metering. Mac

 

[mac west]

Another example first shot DFM focus second one auto only happens at 50mm. I cant figure out why it misses at the long end up close. Mac

 

[Kaziklu]

Well first up.. you are at the long end close up. It's not a macro lens, it is going to have issues.

Second you have a massive blown out back light. the highlights are totally blown out...


So think about it this way..

you have light coming through the lens that is extremely bright... so bright the sensor is only getting white... with no detail. The light is bleeding around the edges of the small object. (same thing was happening to he turtle)


Basically it makes it very hard for the sensor PDAF to get an accurate reading as there is at least 6 if not 7 or 8 stops of range in that image and you are trying to focus on the darkest item.



Next the lens is not designed to be shot that close up, so motor isn't calibrated to do so as easily (I often can focus Manually on the 18-55 closer than the AF can) It is also at the extreme end of the spectrum.

this is a situation where it isn't focusing because it isn't a situation that it should be focusing. if you use a white card to bounce some light on the subject to bring the scene within the cameras DR. ie not having a blown out highlight larger then the area you are trying to focus on.. directly beside what you are trying to focus on... when it is in shadow at least 5 if not 6-8 stops darker.



so basically the camera is not focusing because you are focusing in extreme back light making it hard for the PDAF to be accurate, on a small object closer than the AF motor is accurate in. Take a step back, and use a fill card to bring the lighting of the object into a light range you don't need to blow out the background so much and you will have more success.

 

[asdf photographer]

Another example first shot DFM focus second one auto only happens at 50mm. I cant figure out why it misses at the long end up close. Mac

Mine does the same thing but is much worse. The long end of the 16 50mm powerzoom and 50-200mm, misses focus frequently and especially in low(er) light where it will hunt at times or not even work at all. Even when shooting outdoors in good light, I've learned to back the focal length off a little from the far end, so it will focus better.

Hers is a video I took (posted on vid.me) at 50mm:

Loading…

vid.me

At 30mm it finds focus.

I have about at least 30 more videos in different situations, where it misses focus. The weird thing is in good lighting it seems OK.

 

[mac west]

Thanks for the explanation guys I'm so happy that the camera has a way around it by allowing me to focus manually with its excellent magnification etc. Mac