Prime Lenses, Focus Tuning and Entry Level Bodies...

Forkbeard

Forkbeard

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Jim
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I've just bought a 35mm f1.8 dx prime off ebay and it doesn't focus correctly. It's tack sharp, but back focuses. I emailed the seller who is happy to refund me, but he insists the lens is absolutely perfect and that fine tuning will sort the problem. I have a D3200 which doesn't have fine tuning and am wondering whether or not to upgrade my body? I've only just moved to Nikon from Canon (which I also had a prime for that back focused and had to return it - again on a lower end body with no fine tuning), so have no real money invested in the system. Is this a problem I'm going to run into again with primes? And is a body like a D7100 going to be better suited to these faster primes in general (better focus system etc)? I really want this lens to work as it's great to use and really sharp, just this focus problem.
 
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The d7100 will allow you to fine tune the focus but i dont think the advanced AF would actualy make a difference on its own.
Ive had a few 35’s on my 3300’s and not noticed a problem,could be bad luck,
If you get your money back then buy new from john lewis you have 30 days to try it and get it changed if its not suitable
 
Out of curiosity have you had a look at your settings to see what your AE-L/AE-F is set to!? It might be set to AE-ON hence the problem back focusing?
 
Bodies and lenses are made to tolerances, a lens/body combo might work or it might not depending on which way "out" each of them is. Happens on all lenses not just primes and all bodies, hence micro adjustment being added to some. You should be able to send the body/lens combo to Nikon/Canon and they might adjust it for you, or get it as good as it can be.

Matt
 
I couldn’t live with a body now without af fine tune, it would drive me mad.

If it were me I wouldn’t refund you for the lens as it’s within tolerance and can be made to work on the right body.

I reallly hate these focusing issues so you have my sympathies!

I do find the more you spend on a lens the less issues you have. I’ve just bought two lenses at close to a grand each and neither seems to require any fine tuning. Cheaper primes tend to need a lot. At least on my bodies.
 
Orangecroc said:
Have you tried it in live view mode?
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Yep, it works fine in Live View, so presumably this means it's the lens not the camera that has the issue? I hate using Live View though!
 
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Oh. So the camera needs to go back then? I'm presuming it's not cheap to have this sorted out...
 
This might have been the wrong thing to do, I'm not sure but you live and learn; I've been on Youtube and seen a video on how to correct autofocus issues by adjusting with an allen key. 200 test shots later and I'm getting the same shots/focus points as I was with Live View. They both match and the resulting images are amazingly sharp. So I try to take a portrait shot (in admittedly bad light) at f2.5 and it focuses on a crisp packet in hand, not on the face. Is this just a natural limitation of the lens?
 
Forkbeard said:
This might have been the wrong thing to do, I'm not sure but you live and learn; I've been on Youtube and seen a video on how to correct autofocus issues by adjusting with an allen key. 200 test shots later and I'm getting the same shots/focus points as I was with Live View. They both match and the resulting images are amazingly sharp. So I try to take a portrait shot (in admittedly bad light) at f2.5 and it focuses on a crisp packet in hand, not on the face. Is this just a natural limitation of the lens?
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This is the kind of question that really needs (1) a more detailed explanation of what you were trying to do, and (2) an illustration.
 
Forkbeard said:
This might have been the wrong thing to do, I'm not sure but you live and learn; I've been on Youtube and seen a video on how to correct autofocus issues by adjusting with an allen key. 200 test shots later and I'm getting the same shots/focus points as I was with Live View. They both match and the resulting images are amazingly sharp. So I try to take a portrait shot (in admittedly bad light) at f2.5 and it focuses on a crisp packet in hand, not on the face. Is this just a natural limitation of the lens?
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Adjusting for AF issues with an allen key is probably not a good thing. I don't know about Nikon but on Canon all that does is alter the resting position of the reflex mirror therefor altering the position of the mirror that projects onto the AF array that can and will cause a multitude of problems, so I would avoid unless you are happy to send the camera in for it all to be reset correctly.

To the other part of your post, as Stewart says more info would be useful but, are you using multiple focus points? If so the crisp packet is more than likely a better contrast for the AF to lock onto that any features on the face, best to use a single AF point and focus on the nearest eye.
 
PhilH04 said:
To the other part of your post, as Stewart says more info would be useful but, are you using multiple focus points? If so the crisp packet is more than likely a better contrast for the AF to lock onto that any features on the face, best to use a single AF point and focus on the nearest eye.
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Single shot mode and recompose as required.
Matt
 
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