Question about 645D sensor points and manual focus

[nudibranches]

Hi,

I've been lurking for a while, reading with interest (probably like many of us) about the 645D.

I actually started with a Pentax SLR back in the 1970s, and then moved to a 6x6 medium format Mamiya 330c and then on to Nikon.

I have a D3 and love it, but I've been looking move back to medium format, I was thinking of going back to film, but the latest crop of MDSLRs has caught my attention.

So, I'm very interested in the 645D and also the Hasselblad H3D 31, and am leaving towards the Pentax.

One question, in terms of manual focus (which I imagine I'd be using most of the time) is it possible to use just one focus sensor point and move it around the viewfinder - eg, so I can set the camera up on a tripod, compose, and then focus 2/3s in or on any object/plane I want simply by moving a single sensor around?

I can do this on the D3 and assume this isn't something unique to Nikon.

Many thanks,

Adrian

[tsjanik]

....One question, in terms of manual focus (which I imagine I'd be using most of the time) is it possible to use just one focus sensor point and move it around the viewfinder - eg, so I can set the camera up on a tripod, compose, and then focus 2/3s in or on any object/plane I want simply by moving a single sensor around?

I can do this on the D3 and assume this isn't something unique to Nikon.

Many thanks,

Adrian

Yes you can.  There is a knob next to the eyepiece that when set at "sel" allows you to select the focus point with the arrow keys.  The lack of live view makes manual focus something of a hit-or-miss proposition however.

Tom

[BernardLanguillier]

Yes you can.  There is a knob next to the eyepiece that when set at "sel" allows you to select the focus point with the arrow keys.  The lack of live view makes manual focus something of a hit-or-miss proposition however.

Besides, the focus points occupy a smaller fraction of the frame on the Pentax compared to FX DSLRs. I won't enable you to do rule of thirds focus. On the other hand, nothing can beat DX bodies for such applications.

http://www.google.co.jp/imglanding?imgurl=http://www.fareastgizmos.com/entry_images/0310/10/pentax_645D_viewfinder-thumb-450x337.jpg&imgrefurl=http://www.fareastgizmos.com/digital_cameras/pentax_645d_designed_to_be_the_top_of_mediumformat_digital_slr_cameras.php&h=337&w=450&sz=16&tbnid=4VEddFFC2Q11aM:&tbnh=95&tbnw=127&prev=/images%3Fq%3Dpentax%2B645D%2Bviewfinder%2Bimage&zoom=1&q=pentax+645D+viewfinder+image&usg=__2axY6mKOBY1cfAKpqyxxwJbp3fA%3D&sa=X&ei=Kr8OTbrSGoW8cKn29dEK&ved=0CBwQ9QEwAA

Cheers,
Bernard

[ErikKaffehr]

Bernard,

Thanks for the link!

I absolutely agree with your point on Live View, with the reservation that at least my AF lenses are very hard to focus exactly, because it takes very short motion on the focusing ring to pass accurate focus. Using Live View with Zeiss primes may be a different thing.

Best regards
Erik

Besides, the focus points occupy a smaller fraction of the frame on the Pentax compared to FX DSLRs. I won't enable you to do rule of thirds focus. On the other hand, nothing can beat DX bodies for such applications.

http://www.google.co.jp/imglanding?imgurl=http://www.fareastgizmos.com/entry_images/0310/10/pentax_645D_viewfinder-thumb-450x337.jpg&imgrefurl=http://www.fareastgizmos.com/digital_cameras/pentax_645d_designed_to_be_the_top_of_mediumformat_digital_slr_cameras.php&h=337&w=450&sz=16&tbnid=4VEddFFC2Q11aM:&tbnh=95&tbnw=127&prev=/images%3Fq%3Dpentax%2B645D%2Bviewfinder%2Bimage&zoom=1&q=pentax+645D+viewfinder+image&usg=__2axY6mKOBY1cfAKpqyxxwJbp3fA%3D&sa=X&ei=Kr8OTbrSGoW8cKn29dEK&ved=0CBwQ9QEwAA

Cheers,
Bernard

[nudibranches]

many thanks the the replies!

Mmmmm, yes it doesn't look like the spread of focus points is distributed across a rule of thirds does it?  

At least if I shot the camera in portrait the bottom sensor would be about 2/3s of the way into the plane, so I'm okay there!  

[jduncan]

Besides, the focus points occupy a smaller fraction of the frame on the Pentax compared to FX DSLRs. I won't enable you to do rule of thirds focus. On the other hand, nothing can beat DX bodies for such applications.

http://www.google.co.jp/imglanding?imgurl=http://www.fareastgizmos.com/entry_images/0310/10/pentax_645D_viewfinder-thumb-450x337.jpg&imgrefurl=http://www.fareastgizmos.com/digital_cameras/pentax_645d_designed_to_be_the_top_of_mediumformat_digital_slr_cameras.php&h=337&w=450&sz=16&tbnid=4VEddFFC2Q11aM:&tbnh=95&tbnw=127&prev=/images%3Fq%3Dpentax%2B645D%2Bviewfinder%2Bimage&zoom=1&q=pentax+645D+viewfinder+image&usg=__2axY6mKOBY1cfAKpqyxxwJbp3fA%3D&sa=X&ei=Kr8OTbrSGoW8cKn29dEK&ved=0CBwQ9QEwAA

Cheers,
Bernar

Very useful link. For me the multiple focus points are to close. Too much too close. It's not surprising given that even Nikon / Canon are facing, at this moment, this  limitations.That's one  of the justifications why I am attracted to the Hasselblad's system. Also when shooting still life you can control the focus from the computer and place  it almost at will without moving the camera.
Now, in the other hand,  the H3D-31 don't have true focus.

This could be of some help.
http://www.youtube.com/watch?v=v390U5xZFGc

[BenjaminKanarek]

Yes, like the Pentax K5 and other Pentax cameras i.e. K20D, K7 etc, you can choose the focus points. I;e. Center only, Auto and Manual choices are available.

[BJL]

... the focus points occupy a smaller fraction of the frame on the Pentax compared to FX DSLRs. I won't enable you to do rule of thirds focus. On the other hand, nothing can beat DX bodies for such applications.

http://www.google.co.jp/imglanding?imgurl=http://www.fareastgizmos.com/entry_images/0310/10/pentax_645D_viewfinder-thumb-450x337.jpg&imgrefurl=http://www.fareastgizmos.com/digital_cameras/pentax_645d_designed_to_be_the_top_of_mediumformat_digital_slr_cameras.php&h=337&w=450&sz=16&tbnid=4VEddFFC2Q11aM:&tbnh=95&tbnw=127&prev=/images%3Fq%3Dpentax%2B645D%2Bviewfinder%2Bimage&zoom=1&q=pentax+645D+viewfinder+image&usg=__2axY6mKOBY1cfAKpqyxxwJbp3fA%3D&sa=X&ei=Kr8OTbrSGoW8cKn29dEK&ved=0CBwQ9QEwAA

Indeed, the AF points seem to cover a bit under one third of the frame width, so about 14mm with this 44mm wide sensor: this might be the same spread as with the roughly 24mm wide frame of other current Pentax SLRs. So it seems likely that Pentax reusing the same AF sensor in the 645D as in its "DX" format SLRs? There were signs in the past of Canon (and maybe Nikon) using the same AF sensors in their two different DSLR formats, causing a slightly crowded distribution in the "FX" format bodies, though more recent "FX" format SLRs seem to have their own, better positioned, AF sensors.

If so, such are the burdens in the MF market of producing a camera that will sell less than 1% as many units as the market leaders will sell of their mainstream "APS-C" format models. It is one more reason to dream of Teledyne/Dalsa bringing CMOS sensors and Live View to MF.