Mysterious blank frames on my Pentax 67

[m_c32]

<p>Hi. I've had my Pentax 67 for a year now and have been using it extensively without any problems. Recently, I put 10 rolls through it and to my utter surprise half of these yielded blank (unexposed) frames. <br /><br />This has never happened before. The odd thing is the blanks appeared sporadically -- for example, if I shot three consecutive frames of exactly the same subject, in exactly the same lighting conditions, two would be blank. Frame spacing in all the properly exposed pictures looked normal, so I'm not sure it's a winder or film advance issue. I carry a Sekonic with me too so it's definitely not a case of underexposure either. Furthermore, I distinctly heard the shutter opening and closing each time (hard to miss that sound with the Pentax). Absolutely gutted as I took this with me on assignment and lost some truly promising pictures. Does anyone have any idea what might be causing it? <br /><br />Much appreciated!</p>

[John Farrell]

<p>The shutter may have run across closed.</p>

[thirteenthumbs]

<p>The Pentax 67/67II uses a horizontal travel focal plane shutter.<br>

Normal operation is with the press of the shutter release button the first curtain starts to move across the film plane while the second curtain remains in the cocked position until released by the speed timing. On bulb the first curtain opens and the second remains in the cocked position and the full frame is exposed to light from the lens until the shutter release is released then the second curtain closes blocking light from the lens. As the shutter speed are increased the two curtains form a slit that varies from full frame to 1/8 inch wide or narrower. </p>

<p>A malfunctioning shutter may release both curtains at the same time or the light seal between the curtains may break down causing the first curtain to pull the second curtain with it keeping the film blocked from light. The shutter will sound the same if its operating correctly or incorrectly as just described.</p>

<p>Your camera needs servicing also known as a Clean, Lube, Adjust (CLA).</p>

[allan_jamieson2]

<p>Do you mean half of each roll of 10 was blank or quite literally you had 5 blank rolls and 5 properly exposed rolls of film?<br>

If it was the former, film spacing issues are not uncommon with the Pentax 67 and I had that before with one older body but when that happens what you get is a good exposure and a random unexposed gap then another exposed frame and so on, you might lose the last 2 or 3 frames of your film but won't realise it until you get the film developed. But if you quite literally had 5 blank films and you are sure that they were all correctly exposed, it isn't beyond the realms of possibility that the lab which developed your film might have made a mistake in developing the film, very rare to happen, but not impossible. Worth getting your camera serviced in any case just to make sure that everything is working correctly.</p>

[glen_h]

<p>At slower shutter speeds, you should be able to hear the difference between the above described cases. I would say easily for 1/30 and not so hard for 1/60. Faster speeds, likely not.</p>

<p>(I am more used to the sound of 35mm focal plane shutters, it might be a little different here.)</p>

<p>At anything slower than 1/15, you should definitely hear it, even if you aren't trying to listen for it.</p>

[steve_rasmussen]

<p>I have had my 67 do this but only when the battery is low(not dead). The shutter speeds become way too fast, thus causing severe under exposure that appear to be blank. </p>

[ondebanks]

<blockquote>

<p>Furthermore, I distinctly heard the shutter opening and closing each time (hard to miss that sound with the Pentax).</p>

</blockquote>

<p>Any chance that you were hearing the mirror slap, but not the shutter? Maybe the shutter was not moving at all on those frames. Either way, the solution is as Charles recommended. </p>

[m_c32]

<p>Thanks everyone for taking the time to respond! Grateful for the input. I've brought the camera to two shops here in Tokyo and no one could figure out what the problem was! We tried dry-firing it without a lens (only looking through the front of the camera since the film door had to be kept closed at all times). The mirror appeared to lift normally at all speeds + the back pressure plate of the camera could also be seen, so the shutter is opening at least.<br /><br />Allan, it was the former scenario. The blanks appeared very randomly (scattered throughout rather than concentrated towards the beginning or end of the roll) and the frame spacings were very clean. The guys at both shops were able to confirm that there wasn't a problem with the film advance. <br>

Glen, I tried my darnedest but at all speeds it just sounded like a regular mirror slap followed by the shutter closing normally. My ears ARE very poor though :( </p>

[thirteenthumbs]

<p>There is another possibility that Steve touched on in his post.<br>

Are you using Alkaline or Silver Oxide batteries?<br>

If alkaline then there is a good chance they have insufficient power to properly operate the shutter if 3 or more exposures are made in sequence. <br>

Silver Oxide batteries should do better than alkaline batteries but still may fail under camera load.<br>

When checking batteries with a volt meter a battery that reads its marked voltage or lower should be replaced.<br>

A battery tester is better as it will put the battery under load to test it.</p>