Pentax 6x7 focusing issue. Am I the only one?

[joe_st.pierre]

<p>Hello all,<br /><br />I recently bought a pentax 67 with 105 2.4 and have absolutely fallen in love. The biggest problem is that after reviewing my negs my focus is always soft or JUST off. I find it weird because my eye sight isn't that bad and I have never had much of a problem with manual cameras before. My question is if anyone else has this problem and found a solution. Maybe I need to upgrade the screen and if so any suggestions? <br /><br />Shooting this camera is such a pleasure but its aggravating getting back unusable images.. Please help! </p>

[harveysteeves]

<p>Back when I owned that camera, I had that problem as well. Solution? Sold the camera. Well, I've got another one and will try again.</p>

[joe_st.pierre]

<p>Well thats not the answer I was looking for Harvey hahaha </p>

[rick_drawbridge]

<p>Could be that the height of your focusing screen needs calibrating. This is a perennial problem with old Bronicas with the decay of the rubber shims, but I've not experienced this issue with the Pentax. Put the camera on a sturdy tripod, fit the lens, remove the prism, set the lens to infinity and check the image on the screen with a strong loupe. The rest of the procedure is outlined in this thread:<br>

http://www.pentaxforums.com/forums/48-pentax-medium-format/228502-pentax-67-focus-problem.html</p>

[rick_drawbridge]

<p>Also, a handy post here at: http://www.photo.net/medium-format-photography-forum/00UBNL</p>

[glen_h]

<p>I think I have wondered about this as long as I have known about SLRs (specifically, with non-changeable screens).<br>

The adjustment assumes that the lens to film focus is right, but are you sure about that?<br>

Should you put a ground glass screen on the film plane to be sure?</p>

<p> </p>

[john_shriver]

<p>Send it Eric Hendrickson. He'll get it adjusted. Could be focusing screen location, could be mirror angle.</p>

[tim_bradshaw1]

<p>I have a 67 (II) and it doesn't have this problem so it's not univerasal. As others have, I'd guess it's a difference in the effective position of the focussing screen and film plane, which should be fixable (I've had another (35mm) SLR which had this problem, which I got fixed).</p>

[John Seaman]

<p>I've never had one of these, but I know they've got a reputation like many MF SLR's for vibration causing camera shake when the camera fires, unless the mirror's locked up, or the camera's on a sturdy tripod. Could this be the cause of the loss of sharpness, rather than focus error? Just a thought.</p>

[michael_darnton2]

<p>Crank it back to infinity, see if you think it's in focus there, on something a couple of miles away, as near as you can tell. If not, then mirror or screen are off. I have never seen a screen move on its own, but mirrors, slamming up and down, do.</p>

<p>Usually on most cameras there's a mechanism on the support the mirror rests against in the down position that allows some adjustment. Usually the way it works is the mirror pounds the support down, which means the camera will consistently back focus--your image will consistently be focused behind where you intended. Paradoxically, in the camera this will be more visible with wide angle lenses; on film, not so much with w/a.</p>

<p>If this is the case, and you can figure out the adjustment, you can move bottom of the mirror up a bit, incrementally, until the camera will focus correctly. The movement necessary to make the adjustment will be virtually invisible to you, and if it's screw driven there will be other difficulties that may make it desirable to send it in. On some of my cameras you just need to bend a finger less than you can see and that does it.</p>

<p>If it focuses behind sometimes, in front others, the problem is you, not the camera.</p>

[rick_drawbridge]

<p>From 30 years experience with the Pentax, I sometimes wonder of the whole mirror slap/vibration thing has become something of an urban legend. On a good day, I can hand-hold the camera with standard or wider lenses at 1/30th and get images with no sign of shake. Most of the noise occurs when the shutter fires and the mirror returns to the down position, after the exposure, and the mirror is in the up position before the shutter curtains open... I suspect the whole noisy procedure is suggestive of vibration that possibly doesn't occur at a critical time in the exposure; the big shutter curtains are probably a more likely source of internal vibration. With the Bronica S/S2 the complex mirror slides down and forward out of the light path, and despite the racket I've not noticed any vibration issues at speeds as low as 1/30th.</p>

[Argenticien]

<p>Rick, I concur on mirror slap, at least as far as the Bronica is concerned. I'm quite rusty at physics by now, but it seems to me this vibration should be a self-solving problem. The larger FP shutters and mirrors of 6x6 and 6x7 cameras should need larger force to start or stop them moving (as compared to 35mm cameras). But those same MF cameras also have commensurately greater inertia, due to their considerable heft, so the resulting vibrations should work out to be no worse than those in a 35mm SLR (<em>ceteris paribus</em>).<br /> <em>--Dave</em></p>