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- Andy
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Just got myself a Nikon D90 earlier this month and after a few trips out, producing pictures that were somehow less 'sharp' than I expected, I realised that I have a back-focus problem. What's more, it's with the camera and not with any of the 5 lenses that I've used with it - they all work fine on my D700 :shrug:.
I know that there are tests out there on the Interweb, where you can print off test charts and measure the degree of back/front-focus, but I've drawn my conclusion from my own simple (but 'real world') tests.
As an example, here are two shots of the same subject, using the same lens, but on two different cameras. The subject is a pair of identical CD covers, set up next to each other, but with the CD on the right hand side about 1" further away from the camera than the one of the left. Camera was about 8 feet from subject.
In the first example, you can see (just about; the upload quality is not great, but it's easier to see on the larger versions in the links and impossible to miss on the RAW files) how the Nikon D700 has accurately focused on the selected focus point (these red brackets are from the RAW file and show the selected AF point).
D700
(N.B. I had the in-camera sharpening set to zero in the D700, so it's harder to tell the difference on these jpegs, but when you see the RAW files, it's clear).
Larger ...
However, using the same lens on my D90 and selecting an AF point on the nearest (left hand) CD cover, results in the AF point being slightly OOF and the sharpest area of focus is actually (in this case) 1" behind it, on the right hand CD cover. This is the same degree of back-focusing that I get on most of my captures from this camera/lens combination, at various focal lengths.
D90
Larger ...
So, I have two questions please:
1. Has anyone else here had any recent experience of back-focus problems on a digital camera (not a lens) and how was it resolved :shrug:?
2. Should I be able to claim that the camera is 'faulty' and get it replaced by the retailer (under the "Sale of Goods" act), or is this likely to have to be done under warranty ?
Thanks in advance for your input.
I know that there are tests out there on the Interweb, where you can print off test charts and measure the degree of back/front-focus, but I've drawn my conclusion from my own simple (but 'real world') tests.
As an example, here are two shots of the same subject, using the same lens, but on two different cameras. The subject is a pair of identical CD covers, set up next to each other, but with the CD on the right hand side about 1" further away from the camera than the one of the left. Camera was about 8 feet from subject.
In the first example, you can see (just about; the upload quality is not great, but it's easier to see on the larger versions in the links and impossible to miss on the RAW files) how the Nikon D700 has accurately focused on the selected focus point (these red brackets are from the RAW file and show the selected AF point).
D700
(N.B. I had the in-camera sharpening set to zero in the D700, so it's harder to tell the difference on these jpegs, but when you see the RAW files, it's clear).
Larger ...
However, using the same lens on my D90 and selecting an AF point on the nearest (left hand) CD cover, results in the AF point being slightly OOF and the sharpest area of focus is actually (in this case) 1" behind it, on the right hand CD cover. This is the same degree of back-focusing that I get on most of my captures from this camera/lens combination, at various focal lengths.
D90
Larger ...
So, I have two questions please:
1. Has anyone else here had any recent experience of back-focus problems on a digital camera (not a lens) and how was it resolved :shrug:?
2. Should I be able to claim that the camera is 'faulty' and get it replaced by the retailer (under the "Sale of Goods" act), or is this likely to have to be done under warranty ?
Thanks in advance for your input.