Focusing Issue - New Lens

  • Thread starter Thread starter Paul Kerton
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Paul Kerton

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Hi budding photographers,
Purchased a new lens today (Nikkor AF S 50mm f1.4 G) and although I took a few shots in store, when I got back to my hotel, I found that it did not appear to focus correctly.
Mounted on a D7000 at f1.4 (ISO 100 / 1/100th sec minimum) and on auto focus (single focus point/S or C) it focused approx 10mm behind my intended focus point.
Made for shooting a face near on impossible - Rear eye sharp as opposed to front eye!

Obviously minimal depth of field. When switching to manual it worked fine!
Even when changing to f5 the problem was still apparent (but less obvious!)

Bought from World Camera in the Phanthip Plaza Bangkok and luckily paid going rate with Nikon World Wide Warranty (did consider Grey market but glad I opted out!)
Will go back to shop tommorrow but believe I will probably have to visit Empire Tower again (took a lens in only last week for repair although they provided an excellent service - Nikon Services - Thailand)

Has anyone seen this problem with this lens before! (or could it be my D7000 as opposed to the camera?)

Thanks in advance,

Paul.
 
When you get to F1.4 it's such a fine slice in focus it will often appear hit and miss.
This applies to pretty much any lens that opens this much.
Does this camera have lens specific micro-adjustment?
You don't really often need to be so extremely wide open - it will probably be far more reliable at F2 or so.
Since the subject only needs move a few millimetres it is asking a lot unless on a tripod and doing something that can't move.
 
Seems as though this is not isolated. I took the lens up to f5 on a tripod and shot at a static subject (text on the box which the lens came in ironically)
Although depth of field obviously increased the problem remained.
There are many forums with suggestions that the depth of field is a fine line! but the lens should focus on your chosen focal point (even at f1.4!)
With NCFC losing to Suarez today, I
will put it down to a bad day and visit the store tommorrow.
 
Used the Auto focus Fine adjustment (located in menu) to correct the focusing and know it appears okay although that said it would be better to get the factory calibration done instead. Guess this could be done under warranty for free?
Any further comments welcomed - regards
 
Paul Kerton said:
Used the Auto focus Fine adjustment (located in menu) to correct the focusing and know it appears okay although that said it would be better to get the factory calibration done instead. Guess this could be done under warranty for free?
Any further comments welcomed - regards
Click to expand...

Reading your first post, it sounds like a focus-recompose issue, which naturally puts the focus point slightly behind when a) you're shooting close, b) with a very low f/number, and c) the subject is off centre. Explained here http://www.visual-vacations.com/Photography/focus-recompose_sucks.htm

Having experimented a bit with this, I think that link exagerates the problem and it really only crops up when all those three conditions above apply. More likely is the subject moving slightly, or the camera, between focusing and shooting. Even normal breathing moves things a few mm!

The point I want to make is check things carefully before applying micro AF adjust, with a flat target at a reasonable distance, tripod etc to rule out user error. Lots of threads on micro AF adjustment if you search (eg against my user name). It's a common problem that often turns out not to be an equipment issue, but if it is, then that's what AF micro-adjust is for.
 
iPhoto said:
Richard, that short simple article has just changed the way I will focus for portraits forever :thumbs:

Mark
Click to expand...

It's certainly something to be aware of, and while the theory always holds good, in practise focus-recompose using the centre AF point is a very good method. I use it almost all the time, as do many others.

The theory only becomes signicant under quite unusual circumstances, ie very close, very shallow DoF, and subject well off centre. If it's a prortait for example, you will get better perspective and better bokeh by moving back and shooting with a longer lens. And by doing that, the focus-recompose angle of shift will be substantially reduced and the whole problem goes away.
 
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