The joys of "Good enough"

[Greg Beetham]

Barry I recently read an article (sorry don’t have the link to hand at the moment but I’ll find it if you want it) about fast-ish lenses changing focus point when stopped down (the focus point moves away from the camera due to spherical aberration) so it may be that in setting the camera focus point slightly in front on D90 #1 (depends on just how much in front of course) could be a good thing if you don’t always shoot wide open.
If you use a given lens mostly at f4 or f5.6 it could be that the focus point has become pretty much spot on at that f-stop. Conversely if the focus point is set to be spot on at the fastest aperture by the time it’s stopped down to a working aperture the focus point moves behind where it was before i.e. back focus.
There was a caveat though, it also said that spherical aberration should be minimised down to a small deviation in modern lenses because most of them have aspherical lens elements anyway these days which makes lenses much more compact than they otherwise would be and also corrects spherical aberration, it just remains to be seen how much manufacturers ‘take advantage’ of that and push the limits to such an extent that one ends up with a certain amount of spherical aberration anyway.
As I recall the reason why spherical aberration causes the PDAF system problems was that most of the light coming in to the AF array is transmitted through the greatest area of the lens i.e. the outer ‘area’ is bigger than the middle ‘area’ so if spherical aberration is present that area with a different (shorter) focus point to the centre is dominant, and when the lens is stopped down (during the shot) that area is no longer contributing to focus so the centre area ends up back focussed in the actual photo.
Greg
Ps Bit of an eye opener that article Tom, it seems that the biggest casualty these days with potentially high quality and desirable items is QC, and that too me is a complete mystery, why bother going through the motions of investing a huge amount of money designing something, creating the infrastructure and tooling up, paying people to manufacture it, only to have it all undone by not following through with proper QC…it doesn’t make any sense when their reputation is at stake.

[bfitzgerald]

Problem is Greg I often shoot wide open and this is going to be an issue for me. It depends on the distance to subject/focal length and aperture, sometime's it acceptable..but other times it's not good esp if you do closer up shots. It's certainly better v the original AF which was frighteningly bad, sadly the second D90 was even worse

I've written a letter to Nikon UK explaining the situation and expressing some frustration in a polite way that despite buying 2 brand new D90's from official Nikon sources, and a trip by one to service, I still don't have a satisfactory working acceptably accurate body to use. At the end of the day I paid for 2x D90's and expect them to work as they should brand new out of the box. The ball is in Nikon's court now..but if they can't get this one sorted out (and I'm not paying out for service postage any more) then I'll have to look at other options available to me. It is a real shame as the D90 is just about ideal for me, get along great with it. If only I could get one that had accurate auto focus. It can't be that hard, the Km5d's I have are good..the film bodies are good too. What's the big deal?

Maybe they hired some goons at the factory, or maybe a few of the guys are annoyed and didn't bother to do the AF calibration properly. Honestly the second D90 was so bad..it made the first one look not that bad at all. I've never seen a camera so far off with it's AF, heck a beaten up vivitar would have done better!
I also got a message from Thom Hogan who was not so pleased at my stance on this, I've replied as honestly as I could. He's trying to say it's more likely user errors, settings, focus shift. Well come on over Thom because this is about as real as it gets!

Quite annoying really the entire episode. I am convinced it's a QC problem at the factory. 2 different bodies, bought from different batches/countries even. Serial numbers well apart. Both iffy AF..that's unquestionably a factory issue. As for service well you'd think they would slap the camera in live view and test that v the phase detect, they clearly didn't though

Who knows I might end up with a 5d MkII and work from there. End of the day I need a camera to take photos, and spend less time sending stuff off, writing letters, testing stuff..and more time being able to use the damn thing!

[bfitzgerald]

Update on this I got in touch with Nikon directly and they've told me they "can't find fault" with the camera or duplicate the issue
So I sent this on to them

http://s24.photobucket.com/albums/c25/b ... apture.jpg

I'm linking to it because we have the restriction on image size and you need to see it at a half decent one to appreciate the nice back focus!


I have plenty more of course they mention lenses and they can cause problems, with the wonders of live view AF bypassing the phase detect AF I have ruled that out. Right now I do not have confidence in the D90 I have with me (I can use it but it's not satisfactory), nor did I with the second D90. So I will have to think about my next move on this one. I won't accept the second D90 back if they have not adjusted the autofocus, as for the first one that needs another trip to service and I've told them I'm not paying for posting either.

Since I got the 17-50mm replaced I have tried all lenses on the original D90 and they all show FF to some degree. None of them show any problems at all using live view AF. I will continue to push the issue until a satisfactory conclusion is reached..whatever that may be.
Whilst I'm not angry with the people I've dealt with at Nikon service, I'm puzzled as to how they can't find fault. I'm starting to lack confidence in the ability of Nikon to identify problems and deal with them.

I'm running out of camera makers to try though..and I am aware of this!

[pakodominguez]

Update on this I got in touch with Nikon directly and they've told me they "can't find fault" with the camera or duplicate the issue
So I sent this on to them

http://s24.photobucket.com/albums/c25/b ... apture.jpg

I'm linking to it because we have the restriction on image size and you need to see it at a half decent one to appreciate the nice back focus!


I have plenty more of course they mention lenses and they can cause problems, with the wonders of live view AF bypassing the phase detect AF I have ruled that out. Right now I do not have confidence in the D90 I have with me (I can use it but it's not satisfactory), nor did I with the second D90. So I will have to think about my next move on this one. I won't accept the second D90 back if they have not adjusted the autofocus, as for the first one that needs another trip to service and I've told them I'm not paying for posting either.

Since I got the 17-50mm replaced I have tried all lenses on the original D90 and they all show FF to some degree. None of them show any problems at all using live view AF. I will continue to push the issue until a satisfactory conclusion is reached..whatever that may be.
Whilst I'm not angry with the people I've dealt with at Nikon service, I'm puzzled as to how they can't find fault. I'm starting to lack confidence in the ability of Nikon to identify problems and deal with them.

I'm running out of camera makers to try though..and I am aware of this!

Karma?
Get in peace with Sony, buy an A57 or an A65 and be happy...

Pako

[Dr. Harout]

Karma?
Get in peace with Sony, buy an A57 or an A65 and be happy...

Pako

I second for the a57.

[bfitzgerald]

Problem is the EVF just not for me. If Sony had an OVF model A57 style I'd have no problems giving it a bash.

[bfitzgerald]

Quick update...amazingly I still do not have a replacement D90 despite sending the whole lot back weeks ago (about 3 weeks to be exact)
I've now lost it with the seller (Pixmania) and I've demanded a full refund (due to the unacceptable delay in processing the return) and I've informed them I will be refusing to accept delivery of a replacement which has probably not even been dispatched anyway. It's unfortunate to have to take this stance but it really should not take long to turn this return around and replace it (I'd say a week in total allowing for delivery/pick up etc)

The entire experience has been a complete nightmare, camera problems, multiple repairs which didn't seem to work, and lastly a seller who frankly is so abysmal in their returns procedure (they didn't even get the information right) I will never ever purchase anything from them again.

It's too late to change systems, I have some stuff coming up in a few weeks, so I will likely have to buy a body from Amazon (not had problems with them in any way)