Nikon D5100 Auto Focus damaged?

[torque6]

I bought a D5100 and a 50mm 1.8G on Friday. Set up the camera as AF-A with single point focus. Took some pic of my transformer collection but found the pics blurry.

These pictures were taken off- centre. Upper lift focus point.

Set the camera with AF-A and Auto focus area and allowed the camera to select focus points for me instead, so D5100 choose the upper left focus point, the one near the centre, and the farthest left AF point.

Took about 15 shots, seems all the same. Red squares are the focus points.

Is my AF focus damaged?

Focal length is F2.8, shuttle - 1/200, iso 200.

Some help would be appreciated.

thank you,

 

[Rashkae]

The shuttle was retired by NASA. I think you mean shutter.

This looks fine. You shot at f/2.8 which means your depth of field is thin. Try f/8 and a tripod.

 

[Octarine]

Another thing to take note: AF sensor type. D5100 has only one AF cross-type sensor in the center, the rest are either horizontal or vertical AF sensors.
Have a look in your manual and see which type sits where and what kind of pattern orientation they recognize. The actual AF sensor area is larger than the marking in viewfinder, so any distinctive pattern around the marking is able to lock the AF - whether this is correct or not is your job to verify.
In addition, to eliminate any general AF problem, you can download the focus test charts (Google knows where) and perform the tests according instruction. Do use a tripod, otherwise no point starting it.
Last but no least: AF sensors need light. Make sure you have sufficient light and avoid the common household fluorescent lights. For setups like your case here get Constant Fluorescent Lamps instead.

 

[rhino123]

First thing, how far away are you from your subject. Read up DOF and yes, to be sure, download a test charge from google and do as what Octarine had advised.

 

[daredevil123]

switch to AF-C instead of AF-A.

You are very near to the subject, thus, the DOF is very very thin, any slight movement and the focus will be off. You need continuous AF to get more shots in focus, because if handheld, there is bound to be movement.

 

[torque6]

Thanks bro for all the replies.

Sorry but my mistake. I meant that both configurations, AF-A single + area I am able to lock focus, just that the images are blurred when using single point focus. So i thought maybe the focusing is damaged. My red square on the images are abit faint, they were added in the images in MS paint to indicate which focus points had been lock on.

Test shots were used with a tripod with strobe (fill light) 1/32 in a bright room, subject is about 1/2 meter away. Images I inserted are cropped to illustrated the blur images. I always thought AF-A + single allows you to focus on a point, thus the area around that point would be clear and sharp. Don't seem to be the case here.

Using AF-A , area focus, the D5100 selected the 3 points (indicated in the 2nd pic) and the image is way sharper when shot with AF-A / Single. That why I had inquired if my focusing was damaged as the "head shot" of the transformer head has exactly the same focus point as the one shot with the single point AF.

Hope that clarifies.

 

[Rashkae]

Thanks bro for all the replies.

Sorry but my mistake. I meant that both configurations, AF-A single + area I am able to lock focus, just that the images are blurred when using single point focus. So i thought maybe the focusing is damaged. My red square on the images are abit faint, they were added in the images in MS paint to indicate which focus points had been lock on.

Test shots were used with a tripod with strobe (fill light) 1/32 in a bright room, subject is about 1/2 meter away. Images I inserted are cropped to illustrated the blur images. I always thought AF-A + single allows you to focus on a point, thus the area around that point would be clear and sharp. Don't seem to be the case here.

Using AF-A , area focus, the D5100 selected the 3 points (indicated in the 2nd pic) and the image is way sharper when shot with AF-A / Single. That why I had inquired if my focusing was damaged as the "head shot" of the transformer head has exactly the same focus point as the one shot with the single point AF.

Hope that clarifies.

Then start learning what depth of field means. Also, a camera will not always get the focus right. With all dslr cameras, it will try to lock on to a spot with the highest contrast, and can be tricked by reflections, etc into believing it's locked on.

 

[torque6]

Then start learning what depth of field means. Also, a camera will not always get the focus right. With all dslr cameras, it will try to lock on to a spot with the highest contrast, and can be tricked by reflections, etc into believing it's locked on.

thanks bro, for the reply. So you are suggesting that at the same distance, Changing from AF-A single focus point to AF-A area focus point ( in this case, the head shot shared the same AF point ; upper left), I have to amended the subject distance or stopped down to achieve acceptance field of sharpness?

 

[Rashkae]

thanks bro, for the reply. So you are suggesting that at the same distance, Changing from AF-A single focus point to AF-A area focus point ( in this case, the head shot shared the same AF point ; upper left), I have to amended the subject distance or stopped down to achieve acceptance field of sharpness?

It does not matter what focus mode you are in. In both shots I can clearly see where the camera focused. You need more depth of field regardless of your focusing mode unless your intention is to only have a little bit in focus

 

[torque6]

It does not matter what focus mode you are in. In both shots I can clearly see where the camera focused. You need more depth of field regardless of your focusing mode unless your intention is to only have a little bit in focus

Yes, i only needed a little bit of focus, which is the toy face. The objective in this discussion wasn't much on DOF , but on the sharpness of the image (notabily the toy's face) given that every thing is the same except for the different focusing mode.

In this case, AF-A single vs AF-A area, where I had achieved better sharpness in my images.

 

[Rashkae]

Yes, i only needed a little bit of focus, which is the toy face. The objective in this discussion wasn't much on DOF , but on the sharpness of the image (notabily the toy's face) given that every thing is the same except for the different focusing mode.

In this case, AF-A single vs AF-A area, where I had achieved better sharpness in my images.

If you only want the face in focus, then logically you should use spot focus and focus on the face. I'm not sure why you're even wasting time with area af when it's not the right setting for your desired effect.

 

[torque6]

If you only want the face in focus, then logically you should use spot focus and focus on the face. I'm not sure why you're even wasting time with area af when it's not the right setting for your desired effect.

Yes, exactly. I did that in my first pic. Indicated by the faint red square on the first pic, but the image came out blur at 2.8. Changed to AF-A area at 2.8, maintaining same distance and the pic was sharp.

Hope that clarifies. thanks,

 

[Rashkae]

Yes, exactly. I did that in my first pic. Indicated by the faint red square on the first pic, but the image came out blur at 2.8. Changed to AF-A area at 2.8, maintaining same distance and the pic was sharp.

Hope that clarifies. thanks,

I cannot see any red square there. FYI, your focus is on the numbers at the shoulder. Is this a cropped pic? The AF area is a lot bigger than the tiny squares you are drawing in. If the shoulder area was in the same focusing zone as the head, it may have gotten a higher contrast on the shoulder and focused on that.

 

[torque6]

I cannot see any red square there. FYI, your focus is on the numbers at the shoulder. Is this a cropped pic? The AF area is a lot bigger than the tiny squares you are drawing in. If the shoulder area was in the same focusing zone as the head, it may have gotten a higher contrast on the shoulder and focused on that.

Ya, i drew 1 tiny red squares on the toy nose on the first image. (This was done thru single point). and drew 3 tiny squares on the toy nose, left and right shoulders for the 2nd image. (this was done by Area AF). The red points denotes the focus points lock-on on the d5100 when i took the shot.

Very observant bro, yes the image on the numbers are very sharp in the first pics. You are right , it could have gotten a higher contrast on the shoulder and focused on that.

I was wondering where could I determine the area for each focusing zone on the view finder, since it only displays as black dots?

 

[torque6]

Just for reference. thanks,

Using AF-A , single focal point where red circle = toy's head. (numbers on the back got focused on due to higher contrast)

Using AF-A, Area AF where red circle = toy's head, green circle = left and right shoulders. (overal toy's head is sharp)

Thus the AF-area is able to pick up the best option for me vs if I had used single point. Of course if I wanted to focus on the numbers, single point would do well in another case.

 

[Octarine]

Very observant bro, yes the image on the numbers are very sharp in the first pics. You are right , it could have gotten a higher contrast on the shoulder and focused on that.
I was wondering where could I determine the area for each focusing zone on the view finder, since it only displays as black dots?

As mentioned, the AF sensor area is bigger, even bigger than the bracket area in your AF schema that you posted here. In such a case, where the AF sesor area is bigger than the actual object it is very likely that the focus locks on something else. The numbers give a very contrasty pattern - and that's what the AF sensor tries to find and to lock on. The solution is manual focus where you have full control. But unfortunately, the standard focusing screens and standard auto focus lenses are of little help for manual focusing. Best would be using at least a manual lens with their large focus throw (that's the amount you need to turn the focus ring from closest distance to infinity). A focusing screen for manual lenses will help further. There are different types, ranging from split screen in different forms to special laser finish that lets the area in focus become very sharp and clear. Have a look into the discussions about alternative lenses.

 

[Rashkae]

As mentioned, the AF sensor area is bigger, even bigger than the bracket area in your AF schema that you posted here. In such a case, where the AF sesor area is bigger than the actual object it is very likely that the focus locks on something else. The numbers give a very contrasty pattern - and that's what the AF sensor tries to find and to lock on. The solution is manual focus where you have full control. But unfortunately, the standard focusing screens and standard auto focus lenses are of little help for manual focusing. Best would be using at least a manual lens with their large focus throw (that's the amount you need to turn the focus ring from closest distance to infinity). A focusing screen for manual lenses will help further. There are different types, ranging from split screen in different forms to special laser finish that lets the area in focus become very sharp and clear. Have a look into the discussions about alternative lenses.

Or just re-try focusing on the head till it locks on correctly. ;-)

 

[daredevil123]

My bet is on hand movement actually.

 

[TheFuhrer]

If you really wanna test if your AF point is damaged, why not shoot a chart - something 2D - instead of a 3D object like your toy? Shooting something 3D (like your toy) has many factors contributing to the fact why your pictures are not sharp (i.e. in focus). If you shoot a chart and there's blur, it is for certain that your camera is a dud. However, in most cases it is most likely not.

What I think is that you got confused understanding between AF points and DOF.

Let me take your example and based on your information, you shoot at f/2.8, FL of 50mm, a Nikon D5100 and 50cm away from the toy (close to minimum focusing distance), that should put your total DOF at ~1cm. So is your toy thinner than 1cm? I think most likely not, and so there will be "blur".

And because your camera focus on a particular point, does not mean that it focuses where you want it to be. An AF point is sometimes larger than the dot you see in your viewfinder, and sometimes it chooses a more "contrasty" area within the AF point to focus.

So the recap, your toy is wider than 1cm in width, added the fact that the AF point may get it wrong, the resulting image is what you get. If you really want everything to be nice and focused, I would do is what Raskae and many other suggested, to close down the lens to f/8 (total DOF of 3cm) or f/16 (total DOF of 6cm), focus dead centre on the toy and shoot.

Hope this helps. Cheers.

 

[catchlights]

you want to do a focusing test, download and print out a focusing test chart, follow the instruction closely, else the test you had now is not conclusive.


but if you keen to shoot small subjects like this, best way is to use Live View to do manual focusing, bear in mind that at f2.8, the depth of field only cover about 1cm, ideally you should use f11 or smaller aperture for adequate coverage depth of field.