[Lord Lucan]

the 'Flash Sych Speed' of 1/75th is just not fast enough for fill-in outdoors -- when i was doing my local press photography the rival snappers had Nikons which synched at 1/250th when I was struggling with 1/75th

Were you using the LX later than its prime time? The contemporary professional rivals to the LX in the early 1980's were the Nikon F3 and the Canon "New" F-1.. They had sync speeds of 1/80 and 1/90 sec respectively, so there was nothing significant in it. Nikon's professional line did not reach 1/250 sec until the F4 in 1988, by which time Pentax was making no further effort to keep in the pro market.

Sync speeds did not generally start rising above 1/100 sec until the mid 1980's, when it became a selling point.

[Wheatfield]

Were you using the LX later than its prime time? The contemporary professional rivals to the LX in the early 1980's were the Nikon F3 and the Canon "New" F-1.. They had sync speeds of 1/80 and 1/90 sec respectively, so there was nothing significant in it. Nikon's professional line did not reach 1/250 sec until the F4 in 1988, by which time Pentax was making no further effort to keep in the pro market.

Sync speeds did not generally start rising above 1/100 sec until the mid 1980's, when it became a selling point.

And that was with vertical running shutters that had to prove their reliability in amateur cameras before pros would trust them.

[LesDMess]

As an aside, this won't work without film in the camera, as the meter reads off the film plane for longer exposures.
Put a piece of undeveloped film across the shutter window, or else exposures will all just go to infinity.
One of the claims to fame of the LX was that when used on automatic during longer exposures (longer than 1/30th IIRC) it would adjust exposure during the exposure if the scene brightness changed.

The LX's meter is always reading OTF at all speeds and you can conduct the test I outlined with no film installed. However, having film installed will provide the proper reflectivity as opposed to the pressure plate when film is not installed.
In manual mode, all speed settings - sync speed and above, are mechanically timed while all speeds below are electronically timed. By setting it at lower speeds - like 1, 2 & 4 seconds, it is easy to verify the accuracy using a stop watch.
In aperture priority AE, shutter time is electronically controlled and takes all settings into account - f-stop, ISO and exposure compensation. The meter is always active during AE and will adjust exposure time - up or down, depending on changes in scene lighting. In this mode, one can test that all those controls are working properly.
I made a short video that shows this.

Youtu.be

Youtu.be

I've done a much more controlled test with film with exposures lasting hours long.

[Wheatfield]

The LX's meter is always reading OTF at all speeds and you can conduct the test I outlined with no film installed. However, having film installed will provide the proper reflectivity as opposed to the pressure plate when film is not installed.
In manual mode, all speed settings - sync speed and above, are mechanically timed while all speeds below are electronically timed. By setting it at lower speeds - like 1, 2 & 4 seconds, it is easy to verify the accuracy using a stop watch.
In aperture priority AE, shutter time is electronically controlled and takes all settings into account - f-stop, ISO and exposure compensation. The meter is always active during AE and will adjust exposure time - up or down, depending on changes in scene lighting. In this mode, one can test that all those controls are working properly.
I made a short video that shows this.

LX Manual and Auto metering - YouTube

I've done a much more controlled test with film with exposures lasting hours long.

Not quite. It takes it's reading off the leading curtain. At higher speeds in auto, I believe above the sync speed, the meter reads off the leading curtain and locks in the shutter speed. The system isn't responsive enough to do otherwise at higher speeds. In auto if conditions allow, meaning lower shutter speeds, it takes an initial reading off the leading curtain (this is why it has a dot pattern on it) and will adjust that speed if the light intensity changes during exposure.
All tests with the LX are best done with something more reflective than the pressure plate.

[LesDMess]

Not quite. It takes it's reading off the leading curtain. At higher speeds in auto, I believe above the sync speed, the meter reads off the leading curtain and locks in the shutter speed. The system isn't responsive enough to do otherwise at higher speeds. In auto if conditions allow, meaning lower shutter speeds, it takes an initial reading off the leading curtain (this is why it has a dot pattern on it) and will adjust that speed if the light intensity changes during exposure.
All tests with the LX are best done with something more reflective than the pressure plate.

OTF plane metering includes curtains and film itself. For simplicity and ease of the testing, I recommended the longer shutter speeds. I just wanted to show that you don't need film for this testing and if does not go to infinity.

[gofour3]

For a so-called 'Professional' camera the LX has been disappointing - I have 2. an early and ,later one. The Earlier one has exposure trouble, the later one has the infamous' Sticky Mirror Syndrome' so I have not used them for a long time -- also the 'Flash Sych Speed' of 1/75th is just not fast enough for fill-in outdoors -- when i was doing my local press photography the rival snappers had Nikons which synched at 1/250th when I was struggling with 1/75th and risking movement and a very small aperture in bright light even with 100ASA C41 film. I used my ME Supers more with 1/125th flash synch speed.

Were you using the LX later than its prime time? The contemporary professional rivals to the LX in the early 1980's were the Nikon F3 and the Canon "New" F-1.. They had sync speeds of 1/80 and 1/90 sec respectively, so there was nothing significant in it. Nikon's professional line did not reach 1/250 sec until the F4 in 1988, by which time Pentax was making no further effort to keep in the pro market.

Sync speeds did not generally start rising above 1/100 sec until the mid 1980's, when it became a selling point.

The Pentax K2 had a flash sync speed of 1/125 sec and it was released in June, 1975. That (and the K2DMD 1976) were the only Pentax cameras in the 1970's to have that high flash sync speed.

Phil.

[LesDMess]

The 1962 Ricoh Singlex was equipped with vertical shutters and a sync speed of 1/125 sync speed . . .

[acoulter]

Your tips have really appeared to have helped! The camera sounds as though it is exposing properly again. I'll be dropping off film for development tomorrow for confirmation but thank you! Now I have a question about my viewfinder. It appears quite dirty. I've taken off the prism, blown air, changed the focusing screen but it's still very dirty. Any suggestions?

[stevebrot]

The 1962 Ricoh Singlex was equipped with vertical shutters and a sync speed of 1/125 sync speed . . .

Yep, the original Copal "Square".


Steve

[stevebrot]

Not quite. It takes it's reading off the leading curtain. At higher speeds in auto, I believe above the sync speed, the meter reads off the leading curtain and locks in the shutter speed.

Yep...the reading must be taken before the trailing curtain begins its travel. OTF is only done at or below the sync speed.


Steve

[Wheatfield]

Your tips have really appeared to have helped! The camera sounds as though it is exposing properly again. I'll be dropping off film for development tomorrow for confirmation but thank you! Now I have a question about my viewfinder. It appears quite dirty. I've taken off the prism, blown air, changed the focusing screen but it's still very dirty. Any suggestions?

I'd have to pull my remaining LX apart to be sure, but it seems to me there is a cover glass between the screen and the prism. It's really delicate work in there, and the screen is VERY delicate. It will scratch is you look at it sharply.
Also, make sure it isn't inside the prism. Look through it while it's off the camera.

[acoulter]

It's been a minute but I just wanted to circle back with a moment of gratitude. First, this forum is an endless stream of joy for me. I love reading about everyone's Pentax experiences. As for my LX, she is operating perfectly again. I cannot say thank you enough. It seems she was just a bit out of practice and with all your tips to get her back into action, she's once again good as new. My heart sings.

[Eyewanders]

It's been a minute but I just wanted to circle back with a moment of gratitude. First, this forum is an endless stream of joy for me. I love reading about everyone's Pentax experiences. As for my LX, she is operating perfectly again. I cannot say thank you enough. It seems she was just a bit out of practice and with all your tips to get her back into action, she's once again good as new. My heart sings.

Excellent to hear! A smoothly shooting LX is, in my opinion, nearly as good as it gets. I've almost picked up a late model dozens of times over the past 6 or 7 years but always back out at the last minute. Mine (an earlier serial) still works well enough that I just decided to let it be. It can't be my daily driver but I still love each time I pick it up. My MXs are the workhorses that I abuse, along with a couple of Konica in more recent years. The T4 below has taken top-spot for a daily driver for over 2 years now running, arguably becoming my "favorite", but the LX (and MX) are hair's breadth behind.

[pentaxpete]

I had another look at both my LX's -- I bought the earlier one in 1987 S/N 5238305 10th October for £250 -00 i FOUND the receipt It had lain Un-used for years at back of my Cupboard until I read that 'Dodge' -- the same as you do on a faulty ME Super to rotate the Exposure Compensation and ASA dials back and forth. There is nothing 'sticky' on the underside of the mirrors and both mirror bumper foams are still good --- I have replaced them in my ME Supers. On the LX's I wonder if i should touch a MINUTE amount of oil into the hinge on the mirrors on both sides --

[ralea1313]

That is either the ISO resistor or aperture follower resistor not working right.
Try this: Depress the ISO lock button and rotate the ISO dial back and forth from lowest to highest about 50 times.
The take the lens off and rotate the aperture follower about 50 times as well.
That should clean off any corrosion on the resistors.

Thanks for the tips. They still work in 2021
Really helpful, it made my LX work perfectly again!