Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-22-2012, 11:07 PM   #1
Senior Member
Mock's Avatar

Join Date: Feb 2009
Location: Edmonton
Photos: Gallery | Albums
Posts: 290
Wonky 645 Meter

Picked up a 645 in the local classifieds for $700, came with 45mm f/2.8, 75mm f/2.8, and 120mm f/4 Macro, 4 backs, 2 battery holders, and 23 rolls of 220!

All is well except my camera will not meter properly in any auto mode, no matter what lighting I am in. It thinks it will always overexpose - it flashes 1/1000 f/22 in the viewfinder. If I drop the ISO to 6 and put on a lens cap I can sometimes get it down to 1/1000 f/19. This is with new, fresh alkaline batteries.

Has anyone encountered a faulty meter like this? If so, have you managed to fix it?
It's a long shot, but I am hoping for a quick fix, I don't really want to send it in to Pentax for repair. (if they still fix it)

Overall, it is not so bad...I have managed to make it "work" in metered manual mode by inputting the ISO 4 stops slower than the film speed. (calibrated against my K-5)
However, the meter only reads an accurate exposure as if the lens were wide open. In other words, 1/125s f/2.8 will meter "OK" just as well as 1/125s f/22.
When I stop down the aperture I must remember to adjust the shutter speed accordingly before shooting.

Any help is appreciated!

10-23-2012, 11:55 PM   #2
Veteran Member
FrankC's Avatar

Join Date: Dec 2011
Photos: Gallery
Posts: 318
People who may know will need to know which 645 you have (645, 645N, 645N II).
10-30-2012, 06:14 PM   #3
Senior Member
Mock's Avatar

Join Date: Feb 2009
Location: Edmonton
Photos: Gallery | Albums
Posts: 290
Original Poster
Well, if it were a 645N, 645NII, or 645D, I would have written one of those things. The lack of any letters or roman numerals should be understood quite readily I should think.
10-31-2012, 04:42 PM   #4
Forum Member




Join Date: Mar 2011
Location: Northants, England
Posts: 97
Very frustrating, especially as so far no-one seems able to help. It sounds as if a repairer's help is needed.It doesn't sound simple like a tweak of the controls or cleaning electrical contacts. If you were in the U.K I could recommend at least one very competent repairer and I am sure there are others but as you are in Canada that's not practical.

Hopefully someone will be able to help.

asahijock

10-31-2012, 06:16 PM - 1 Like   #5
Giveaway winner!
MysteryOnion's Avatar

Join Date: Dec 2007
Location: beantown
Photos: Albums
Posts: 885
Well, I wanted to stay out of suggesting anything as I have yet to win a broken 645 at auction so as to it take apart...however, my 2 cents worth is this...

The thing that comes to mind first off is if the push button method of setting speeds relies on a usual memory function.
The pressing of the release button to activate the meter for displaying prior to shooting the picture is not matching the recorded setting that was gathered just a fraction of the second prior to starting the cycle of raising the mirror and opening the curtain.
It seems the first place I would check is the contacts running to and from the release switch and check if the mirror box if it has a contact switch that must be set to confirm the sequence was started properly prior to the mirror going up.
Some contacts do get a little oxidized or even gummed up over time. The other factor is how the control panel buttons are wired and if the connections are soldered or clipped in place and if one of the connections is not communicating well... i.e...a steady pulse at a know value would be computed as 1/250th, but a irregular pulse of the same value might be computed as 1/15th.

This of course is not a spray it and see issue. The repair manual and some familiarity with camera repair is needed.
11-01-2012, 05:46 PM   #6
Senior Member
Mock's Avatar

Join Date: Feb 2009
Location: Edmonton
Photos: Gallery | Albums
Posts: 290
Original Poster
Thanks for your input, MysteryOnion. To be honest, most of what you wrote flew over my head.
Setting shutter speeds works fine, I can get proper exposures reliably, and I do get under or over exposure indication in metered manual mode (lens wide open) when the shutter speed is set off zero. Actual timing of the shutter speeds seems accurate too, I think the issue is aperture specific.

It seems to me (warning: unprofessional opinion) the aperture-lever mechanism camera-side is not making physical contact with whatever circuit it is tied to, which might explain the wide-open metering issue in manual mode. The meter will read wide open because the mechanical linkages have physically opened the aperture all the way, but the camera electronics don't know the stopped-down aperture.

It just seems counter-intuitive that with the lens in "A" setting the meter reads massive overexposure instead of underexposure, much more over-exposure than the 4-stops I have to use to compensate in metered-manual.
It is so much over-exposure I think the camera is calculating backwards - calculating an exposure value 10 stops MORE than wide open. (6 stops lens range assuming f/2.8-22 + 4 built in the meter)
The reason why this could happen eludes me.

Something else of note: When shooting in Aperture-Priority Auto mode the lens does not shoot at the correct electronically-selected aperture, only f/22. I'll enter 2.8 and the lens will close all the way down at exposure.

Looks like I might have to send it in. Shame to be without it for 4-6 weeks, and I fear the estimate will be astronomical.

I would poke around and attempt repair myself if I had a service manual, but as it is I don't even know how to crack it open properly.

Thanks again everybody!

Last edited by Mock; 11-01-2012 at 06:03 PM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, f/2.8, f/22, iso, lens, medium format, meter, mode
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Pentax 645 Leaf Shutter 75mm 2.8, 645-A 150mm F3.5 MightyMike Sold Items 13 04-03-2012 06:47 AM
How to meter if you don't have a light meter? LFLee Pentax Medium Format 25 02-09-2012 11:45 AM
645 Meter Issue 62sunbeam Pentax Medium Format 4 06-10-2011 12:04 AM
Contax 645 lens adapter for Pentax 645/645D? MikeSeb Pentax Medium Format 2 01-18-2011 07:47 AM
Original 645 Meter Halco Pentax Medium Format 2 05-05-2010 04:23 PM



All times are GMT -7. The time now is 07:52 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top