Focusing Problems with new Nikon D750

[Lonnie1212]

Hi Folks,

Last week I bought a new used D750 from Roberts Camera. I have been thoroughly impressed with the camera until today. I put a 200-500 Nikon lens on it and went out to the wildlife sanctuary. I had the camera set to Shutter Priority, Auto ISO, and the focus setting was set to AF-C D-9. Those are the settings I have successfully used with the D610 for the past 3 years. Today I had a focusing problem which I've never had before. It totally caught me off guard and I can't explain it. I was using a single focus point as usual. When I would move the focus point to the left side of the view finder the lens would not focus. When I would move the focus pointer to the right side of the view finder it would focus perfectly. I was using the viewfinder and not live view. I took the lens off the camera and removed the battery from the camera as well. I let the camera set for 15 minutes and put everything back together. Now it seems to be working just fine. Does anyone know what could have happened?

Thank you,

Lonnie

 

[PJM]

I'm going to guess you stumbled upon a rare software bug and will likely never see it again. At least that is what I'd be hoping since it went away on a power cycle if it were mine. Good luck.

 

[RAZKY]

Hi Folks,

Last week I bought a new used D750 from Roberts Camera. I have been thoroughly impressed with the camera until today. I put a 200-500 Nikon lens on it and went out to the wildlife sanctuary. I had the camera set to Shutter Priority, Auto ISO, and the focus setting was set to AF-C D-9. Those are the settings I have successfully used with the D610 for the past 3 years. Today I had a focusing problem which I've never had before. It totally caught me off guard and I can't explain it. I was using a single focus point as usual. When I would move the focus point to the left side of the view finder the lens would not focus. When I would move the focus pointer to the right side of the view finder it would focus perfectly. I was using the viewfinder and not live view. I took the lens off the camera and removed the battery from the camera as well. I let the camera set for 15 minutes and put everything back together. Now it seems to be working just fine. Does anyone know what could have happened?

Thank you,

Lonnie

It might not be a bad idea to clean all camera and lens electrical contacts. Good luck!

 

[Lonnie1212]

I'm going to guess you stumbled upon a rare software bug and will likely never see it again. At least that is what I'd be hoping since it went away on a power cycle if it were mine. Good luck.

Thank you PJM

 

[Lonnie1212]

It might not be a bad idea to clean all camera and lens electrical contacts. Good luck!

That's a good idea too. Thank you

 

[mrca]

If there was enough contrast on the one side for the camera to get focus, is it possible there was a low or no contrast where the other focus point is. I had a 400 mm 2.8 and it had no problem getting focus. Also, it it is a 5.6 lens or you stopped down even further, was the one area to dark? When you reattached the lens did you try focusing on a different spot if the camera wasn't on tripod so the failing spot got focus? I find with a 300 f/4.5 at 5.6 or 8 even a d850 has problems confirming focus. Realize your lens has 19 light sucking and reflecting elements sucking the low energy shadow light if you are trying to focus in shadows.

 

[RAZKY]

Realize your lens has 19 light sucking and reflecting elements sucking the low energy shadow light if you are trying to focus in shadows.

f/8 is f/8 whether the lens has 2 elements or 20.

 

[mrca]

f/8 is f/8 whether the lens has 2 elements or 20.

Yes, f/8 is f/8, but just like different lenses rendering different color, with 22 pieces of glass sucking out or reflecting it back, the low energy shadow detail is lost and you get patches of mud and flat images. There is a reason for the terms zeiss pop or leica look. Compare a crap "art" lens with a low element older zeiss. And in b&w which is only contrast, low element count lenses blow away those with 14-22 pieces of glass tubes.

 

[RAZKY]

Yes, f/8 is f/8, but just like different lenses rendering different color, with 22 pieces of glass sucking out or reflecting it back, the low energy shadow detail is lost and you get patches of mud and flat images. There is a reason for the terms zeiss pop or leica look. Compare a crap "art" lens with a low element older zeiss. And in b&w which is only contrast, low element count lenses blow away those with 14-22 pieces of glass tubes.

I'm confused as to how that would affect focus. I have several long lenses and equivalent focal-length and aperture telephotos, and see no difference in focusing them.

 

[mrca]

I'm confused as to how that would affect focus. I have several long lenses and equivalent focal-length and aperture telephotos, and see no difference in focusing them.

If you are using a single spot to focus, a longer lens makes areas in the frame larger. So if you put the spot over an area with little contrast since contrast is what it needs to get focus, it could be difficult getting focus. If your lens has muddy shadows with no detail, instead of the spot covering some detail or edge between shadow and midtone, it could be within the detail/contrast free area. Each piece of glass in a high element count lens reflects light back except the couple that are coated and they all absorb light. Hold your glasses in sun light and note there is a shadow not from just the frames but from the glass as well. Key to getting focus, place the spot with an edge. I spot focus and meter through the same spot. So place the spot on the area just below the eye and that gets me focus as I expose 1 stop brighter than the center hash mark in the viewfinder meter for caucasian skin. Can do that in a split second.

 

[RAZKY]

If you are using a single spot to focus, a longer lens makes areas in the frame larger. So if you put the spot over an area with little contrast since contrast is what it needs to get focus, it could be difficult getting focus. If your lens has muddy shadows with no detail, instead of the spot covering some detail or edge between shadow and midtone, it could be within the detail/contrast free area. Each piece of glass in a high element count lens reflects light back except the couple that are coated and they all absorb light. Hold your glasses in sun light and note there is a shadow not from just the frames but from the glass as well. Key to getting focus, place the spot with an edge. I spot focus and meter through the same spot. So place the spot on the area just below the eye and that gets me focus as I expose 1 stop brighter than the center hash mark in the viewfinder meter for caucasian skin. Can do that in a split second.

Hmmm. Never heard that stuff before! Thankfully, I have no lenses with "muddy shadows."

 

[Lonnie1212]

If there was enough contrast on the one side for the camera to get focus, is it possible there was a low or no contrast where the other focus point is. I had a 400 mm 2.8 and it had no problem getting focus. Also, it it is a 5.6 lens or you stopped down even further, was the one area to dark? When you reattached the lens did you try focusing on a different spot if the camera wasn't on tripod so the failing spot got focus? I find with a 300 f/4.5 at 5.6 or 8 even a d850 has problems confirming focus. Realize your lens has 19 light sucking and reflecting elements sucking the low energy shadow light if you are trying to focus in shadows.

When I had the focusing problems I tried taking pictures in several different areas. It was the same problem everywhere. Finally I disconnected the lens and removed the camera battery. Let it set for 15 minutes. Put it all back together and it worked just fine. Haven't had any problems since then. Thank you for your input. I appreciate hearing from other photographers.

 

[RAZKY]

When I had the focusing problems I tried taking pictures in several different areas. It was the same problem everywhere. Finally I disconnected the lens and removed the camera battery. Let it set for 15 minutes. Put it all back together and it worked just fine. Haven't had any problems since then. Thank you for your input. I appreciate hearing from other photographers.

Removing and replacing the lens and battery wiped the contacts. Thanks for the update.