On-sensor PDAF, will it be as good as mirrored cameras?

Started Oct 10, 2013 | Discussions thread
Bruce Oudekerk
Bruce Oudekerk Veteran Member • Posts: 3,384
Re: Some related thoughts.

Albino_BlacMan wrote:

Z axis movement isn't a new idea... Contax did it with the AX is 1996 (I think that's the year at least). At the time they had to move a whole roll of film so moving a sensor seems minor in comparison (well not minor but it shows it wouldn't be impossible).

There are some shortcomings however as it only really works with wide angle and maybe normal lenses. Anything else needs the sensor to move too far (so it won't work with telephoto lenses) and it can't achieve focus for things like macro (look at an old MF lens (50mm(ish)) and look how far the front element moves to achieve MFD and add that to the depth of the camera).

It's a nice idea but it won't be a game changer and won't help Sony sell lenses.

I knew about the Contax attempt to do this but had no idea how much Z axis movement it could generate and just assumed it wasn't much given the complex issues of dealing with film. I also assumed that any lens would be set on infinity and the Z axis 'throw' of the sensor would determine the MFD.  I realize the longest tele and definitely macro would be severely limited.  (I took one look at my old auto Canon bellows unit to realize this). However these would be a very small percentage of the lenses. If this limited sensor 'throw' can't reasonably accommodate, lets say, a 200mm lens... it will probably just be a curiosity. That focal length of 200mm is probably a good threshold for usability, APS-C or FF. But if it can do this, it would, or could, be amazing. Almost all modern lenses have internal focusing elements but I seem to remember that my oldest manual lenses had what I would think would be a reasonable Z axis 'throw' and thus I assumed it would be possible.

I hope you are being too conservative in you estimates of what can be done but you are dashing my hopes:(


BTW...the link to your Photobucket images broke.

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