11-26-2011, 09:36 AM
[quote name='wim' timestamp='1322265561' post='13249']
That actually is the correct conclusion. All cameras are, unless they are individually aligned to perfection, and no camera maker does this, other than maybe Alpa.
However, it doesn't matter too much if the size of the alignment difference is relatively small, and the number of MP isn't too large (it becomes more noticeable with higher MP counts). This is actually one of the reasons why some landscape photographers using MF backs have gone to aligning their backs individually for optimum alignment with the camera mount, or have it done (if they are separate backs it isn't too difficult to do). And the same is true for the lens mount on dslrs - some people do have it adjusted to align as perfectly as possible with the sensor, or even do it themselves, although this requires some equipment if one doesn't want to let it depend on lots of trials and errors.
Underneath most camera lens mounts there are shims with uneven thickness over their radius in order to correct for this. But it isn't perfect, as those shims are standard shims. The same is true for sensor mounts. Considering the precision required to get it really right, it is amazing that things work as well as they do <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.
BTW, due to the thickness of film emulsion, this generally wasn't a problem with slrs, other than making sure film was flat enough. And alignment was easier with film slrs, as one only had to align the film guides to the lens mount.
Kind regards, Wim
[/quote]
There is, of course, no perfection but if 80% of the results are fine and 20% are suspicious it is also a valid conclusion that the camera is not the problem. And I wouldn't say that 20% is "rare".
The flaw in this article is the assumption that the center sharpness defines the production quality (as shown in their graphs). If they would have a look at the 4 border regions (which is, of course, a substantially higher effort) they would not have choose "rare" to describe the situation.
That actually is the correct conclusion. All cameras are, unless they are individually aligned to perfection, and no camera maker does this, other than maybe Alpa.
However, it doesn't matter too much if the size of the alignment difference is relatively small, and the number of MP isn't too large (it becomes more noticeable with higher MP counts). This is actually one of the reasons why some landscape photographers using MF backs have gone to aligning their backs individually for optimum alignment with the camera mount, or have it done (if they are separate backs it isn't too difficult to do). And the same is true for the lens mount on dslrs - some people do have it adjusted to align as perfectly as possible with the sensor, or even do it themselves, although this requires some equipment if one doesn't want to let it depend on lots of trials and errors.
Underneath most camera lens mounts there are shims with uneven thickness over their radius in order to correct for this. But it isn't perfect, as those shims are standard shims. The same is true for sensor mounts. Considering the precision required to get it really right, it is amazing that things work as well as they do <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />. BTW, due to the thickness of film emulsion, this generally wasn't a problem with slrs, other than making sure film was flat enough. And alignment was easier with film slrs, as one only had to align the film guides to the lens mount.
Kind regards, Wim
[/quote]
There is, of course, no perfection but if 80% of the results are fine and 20% are suspicious it is also a valid conclusion that the camera is not the problem. And I wouldn't say that 20% is "rare".
The flaw in this article is the assumption that the center sharpness defines the production quality (as shown in their graphs). If they would have a look at the 4 border regions (which is, of course, a substantially higher effort) they would not have choose "rare" to describe the situation.