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D750 image sensor replace… AF is not sharp?

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Hermite

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Hello, i managed to replace my image sensor, it had many permanent spots.

Now it’s clean and spotless.

My problem is now with the AF.

During Manual focus, all is good, but when in AF mode it never get sharp.

I get a slight improvement setting it at -20. If i could push it to -35 it would probably look sharp, but -20 is the max. What could be my issue? Could I have screwed in the new sensor a little closer to the lens compared to the placement of the original sensor? It’s screwed in and mounted on 3 springs. I do recall when I was disassembling the sensor that the screws were tightly screwed in… so I proceeded likewise. Must the sensor and the lens be at an exact distance? Perhaps so since it appears I would need to go way pass -20 to get in focus. Any help would be appreciated… and I hope I won’t read too many ´send to Nikon repair shop’🤪
 
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Hermite said:
Hello, i managed to replace my image sensor,
Click to expand...
Out of interest where did you get your replacement sensor - and how much did the replacement part cost?

I presume you had to take the camera body apart as the sensor is bigger than the mirror box dimensions. How complicated was opening up the camera body?
 
Hermite said:
Hello, i managed to replace my image sensor, it had many permanent spots.

Now it’s clean and spotless.

My problem is now with the AF.

During Manual focus, all is good, but when in AF mode it never get sharp.

I get a slight improvement setting it at -20. If i could push it to -35 it would probably look sharp, but -20 is the max. What could be my issue? Could I have screwed in the new sensor a little closer to the lens compared to the placement of the original sensor? It’s screwed in and mounted on 3 springs. I do recall when I was disassembling the sensor that the screws were tightly screwed in… so I proceeded likewise. Must the sensor and the lens be at an exact distance? Perhaps so since it appears I would need to go way pass -20 to get in focus. Any help would be appreciated… and I hope I won’t read too many ´send to Nikon repair shop’🤪
Click to expand...
The level of precision required to perform this work is not something anyone can attempt without proper equipment and alighment instrument. Not only it must be in the right distance but it must also be prefectly parallel with the lens plane - and that those springs are for.
 
Agree, I just read an excellent article on this.

The FFD should be 46.50mm and of course I have no fancy measuring bench tool to perform the adjusrment. I’ll give it one more attempt at loosening the screws… but I sense a permanent failure 😤
 
j_photo said:
Hermite said:
Must the sensor and the lens be at an exact distance?
Click to expand...
Yes
j_photo said:
… and I hope I won’t read too many ´send to Nikon repair shop’
Click to expand...
That's what I would have done to start with.
Click to expand...
Absolutely. I am a very do-it-yourself kind of person and will have a go at many things. Sometimes (not often) I fail. I would have been daunted by a sensor replacement.

@OP: Does the sensor need to be closer to the lens flange? If so, shimming may be required. When you say autofocus is not correct are you focusing via live view or via the focus screen? Test both. If live view succeeds but via the focusing screen does not then the latter may need shims.

I've got to agree with j_photo. Were it I, the camera would have gone straight to Nikon.

Good luck!
 
Hermite said:
Hello, i managed to replace my image sensor, it had many permanent spots.

Now it’s clean and spotless.

My problem is now with the AF.

During Manual focus, all is good, but when in AF mode it never get sharp.

I get a slight improvement setting it at -20. If i could push it to -35 it would probably look sharp, but -20 is the max. What could be my issue? Could I have screwed in the new sensor a little closer to the lens compared to the placement of the original sensor? It’s screwed in and mounted on 3 springs. I do recall when I was disassembling the sensor that the screws were tightly screwed in… so I proceeded likewise. Must the sensor and the lens be at an exact distance? Perhaps so since it appears I would need to go way pass -20 to get in focus. Any help would be appreciated… and I hope I won’t read too many ´send to Nikon repair shop’🤪
Click to expand...
Have no idea why you replaced the image sensor and so I'm not at all surprised you've now found AF problems. This type of work as far as I'm concerned is an automatic return to Nikon for a proper job to be done.
 
Did the old sensor have scratches from do it yourself cleaning?

Also, unfortunately, I think you know at this point that sensor replacement can only done by Nikon technicians who have the right equipment.
 
An alternative to re-adjusting the sensor distance would be to adjust the AF mirror which should allow you to get into the -35 range you are looking for. However, it won't do much if the sensor isn't exactly parallel to the plate it's mounted on.

Have a look at this link on how to do it - https://leongoodman.tripod.com/d70focuspart3.html - and then you can have a look inside your D750 mirror box to see if the same adjustments are there.
 
Hermite said:
Hi all and thanks for the info. I managed to get in focus by simply unscrewing 4 1/2 turns each of the three screws with a minor AF tuning at the cmos. All good now!
Click to expand...
How did you decide on 4 1/2 turns?
 
Hermite said:
Hi all and thanks for the info. I managed to get in focus by simply unscrewing 4 1/2 turns each of the three screws with a minor AF tuning at the cmos. All good now!
Click to expand...
Well done. I hope all is OK now - you must be getting pretty expert at taking the camera apart!
 
Like others have said, the tolerances are too tight for this to be done at home. Not even a Nikon technician could do this at home. Not only does the sensor have to be exactly where it was or is supposed to be, but Nikon has a machine to calibrate autofocus. This was a well discussed issue and process back in D800/D800E days of the left focus issue that plagued many of the early copies of mostly the D800. So unfortunately you absolutely need to send it in to Nikon for repair, if Nikon will even repair it. You might be screwed for lack of a better word. Nikon could claim that you altered the camera and refuse to fix it for safety or whatever reason. People just think, oh Nikon needs and wants my money, but that is NOT the case. Nikon used to love the term "impact damage" and would use it often. They would refuse to or say the couldn't fix a lens or camera due to impact damage. So I wouldn't be surprised if they don't help you or if they discover you self installed a new sensor, they will send it back to you. Best of luck, but you really should have done some more research before trying that. You might be very skilled at fixing things or fixing camera's and I get wanting to save money. But you got yourself in over your head here.
 
patricksmith32 said:
Like others have said, the tolerances are too tight for this to be done at home. Not even a Nikon technician could do this at home. Not only does the sensor have to be exactly where it was or is supposed to be, but Nikon has a machine to calibrate autofocus. This was a well discussed issue and process back in D800/D800E days of the left focus issue that plagued many of the early copies of mostly the D800. So unfortunately you absolutely need to send it in to Nikon for repair, if Nikon will even repair it. You might be screwed for lack of a better word. Nikon could claim that you altered the camera and refuse to fix it for safety or whatever reason. People just think, oh Nikon needs and wants my money, but that is NOT the case. Nikon used to love the term "impact damage" and would use it often. They would refuse to or say the couldn't fix a lens or camera due to impact damage. So I wouldn't be surprised if they don't help you or if they discover you self installed a new sensor, they will send it back to you. Best of luck, but you really should have done some more research before trying that. You might be very skilled at fixing things or fixing camera's and I get wanting to save money. But you got yourself in over your head here.
Click to expand...
No need for harsh words - he fixed it - congratulate to the OP
 
Oops,

Missed that post or update, my bad. I'm very surprised it worked out, that's impressive!
 
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