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D850 Focus Issue


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4 replies to this topic

#1
hotstonehiking

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Hi folks. I'm new to the forum. Glad to be a part of the community. 

 

I have been in the business for 28 years and just recently became a Nikon person: I was a Canon/Leica/Sony Mirrorless (in that order) beforehand. 

 

Anyhow, just purchased the D850 with a 50 1.4, all new, and I am having an issue. When I use the autofocus and focus on something at a distance ~10-20 feet away, it locks the focus. But I find that I ALWAYS have to turn the focus ring a smidge toward infinity in order to get tack sharp focus. In other words, the AF is just a tad off. 

I called Nikon and the person who was trying to help me kept asking me to send pictures. But that made no sense to me because what am I going to send a picture of? Something that is a SMIDGE out of focus? It doesn't show what the camera is doing wrong to get to that point. Otherwise, he said I could send it in, but techs would simply send it back to me without an example of what was happening. Very frustrating. 

 

Anyhow, does anyone have any thoughts about what is happening here? I know there is an AF fine tuning adjustment. But for some reason he was strongly advising I don't use that. Not sure why. 

 

Any thoughts would be helpful. Including letting me know that I have a lemon and need to return. 

 

Thank you in advance. 

 

p.s. bonus points if anyone knows how I can remove the thin lines in the viewfinder--not the grid lines, but the line shown in the attached picture. Is it on the focus screen? If so, can you buy blank focus screens?



#2
Jerry_

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What you describe sounds like a back/front focussing issue - and this is what the AF finetuning is for.

You can either do it manually (for this you will need to do a hardware setup; you will find details on this forum in related threads) or get software&tools like Reikan Focal Pro to help you.

I don’t know why the technician was reluctant, because it could well be what they will do, too. Obviously when you overcorrect, things will look worse, but then you can still revert or delete the correction.

Using the AF finetuning from the camera menu in the way it is designed should not impact on your warranty.

(Good to know: the finetuning that you will do will be specific for the lens you are aligning with)

PS: I don’t see an attached picture

#3
Bengan

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First of all. When you have issues and ask for help with something, it's always helpful if you supply examples (post photos).

 

Second, any lens-body combination usually needs a AF fine tuning. I'm a bit surprised that you after 28 years haven't experienced this before. Personally, I always start off a new lens with a AF fine tuning/check.

 

Try to post the photo you're referring to again. I can't see it either



#4
Ron

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It's likely that the tech at Nikon asked for a photo file so that he or she could possibly determine if the AF system is front focusing or back focusing. The tech would then very likely try to guide you through the process Jerry described above. If you focused on a flower, for example, but the plant leaf behind it seems sharper, then the camera is back focusing. The adjustment is fairly simple but the proper tools make it more precise.

 

I also can not see the photo you posted.

 

--Ron



#5
hotstonehiking

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Thanks for the responses.

 

Indeed @Bengan, I did get through 28 years without experiencing this before. I guess I was lucky!

 

Here's a link to the viewfinder lines: https://2.img-dpreview.com/files/p/TS560x560~forums/56941646/d1e04edf0c3449cf8d7bc4e119b91086

 

Since posting this query a while ago, I have learned these lines are etched onto the focusing screen. But I don't think it is possible to purchase/install a blank focusing screen. I know focusingscreens sells one, but I think it is somehow suited for close-up photography/lenses. Still open to thoughts.

 

Thanks.