Shutter times too long...

[florian_ross]

<p>Hi there,</p>

<p>just for the fun of it, I measured the shutter times of my Mamiya 645's and found out that both machines were off. By looking at the numbers I had to realize that body 1 is about +20% off, body 2 almost +50%. Since having those repaired is too expensive I was wondering if there was an easy way to compensate. For the 2nd body, I guess it means "chose the next shorter time available" for the older one, what could be a rule of thumb?</p>

 

Thanks!

[Dustin McAmera]

<p>20% is nothing, I think; certainly within the error you might get just by using reflected-light metering in interesting light. 50% might be worth allowing for, maybe by setting the film-speed half a stop faster. Not sure what the film-speed dial is like though; you may have to choose between one-third and two-thirds of a stop. I wouldn't bother even doing that, unless you're <em>seeing</em> overexposure in your pictures.</p>

[SCL]

<p>In the "golden age" of film photography, film manufacturers assumed that shutter speeds on cameras would routinely be off by up to 20%, and advised photographers, as did camera manufacurers, to bracket their shots.</p>

[jose_angel]

<p>Are yours mechanical cameras?<br />If so, long ago I read an article in a reputable magazine about it. An error smaller than 30% were considered acceptable (for certain manufacturing standards). I was surprised.<br />On electronic cameras, the "acceptable" margin was way smaller, cannot remember how much, but maybe around 3-5%. They tested several mechanical cameras and most of them were quite accurate, far from that 30%... Leica was amongst the best. I think another one was the FM2, which also received a good score.<br />If you know what is the real speed, it is not a problem at all. It is a quite common issue on large format shutters.</p>

[jose_angel]

<p>Double post?</p>

[russ_britt3]

<p>The 645s had electronic shutters.........</p>

[johne37179]

<p>I remember back in the day having to get all of the shutters on all of my cameras periodically recalibrated. My local camera shop could do it then. I suspect that this skill has been lost over the years. However, there may be a local repair shop to do it for you. I'm not sure how the process works, but back then it was neither inconvenient or expensive.</p>

[aplumpton]

<p>Whenever I check my cameras, one of which has a mechanical shutter and another a combination electronic-mechanical shutter, I find that that the errors vary quite a bit according to the chosen speed. I am not sure if you refer to all speeds in your example or just some or the worst ones. Even a mechanical Leica M is quite inaccurate at highest speed (1/1000 sec can be 1/750 sec or thereabouts) and this is also true at highest speed (1/500 sec) for the electronically controlled but mechanical in-lens leaf shutter on each of my Mamiya 6 optics, which otherwise have spot on performance at slow speeds (under about 1/15 sec) and at 1, 2 and 4 seconds. The demands on the physical shutter mechanism at very high speeds is high and not all shutters can respond so well.</p>

<p>Another thing is that the shutter when stressed (that is the shutter has operated more than once in a cycle of shots) can result in speeds that are somewhat more accurate (or consistent) than when just one-off at any particular speed. A 50% error, if it occurs at most speeds and not just the very low or high speeds, is quite serious. I am not a camera specialist but what I do is to calibrate my shutters with a simple little shutter meter (mine was acquired from Calumet) and create a little table of actual shutter speeds (rounded off for easy conversion when measuring light) or simply compensate by adding or subtracting a half stop or less when photographing. The error is often in the same direction so it is just a question of changing the exposure a little like that of making an intentional underexposure.</p>

<p> </p>

[c_watson1]

<p>Which Mamiya 645? Old "heavy metal" or newer Super/Pro/ProTL? Latter are quartz-timed and either work or don't work. Problem now with mechanicals like the Mamiya oldies is finding someone/anyone who can service 'em. Might be time to move on to something newer if a fix is uneconomical. With film and processing getting no cheaper, it's hard for me to live with wonky and/or semi-functional cameras.</p>

[florian_ross]

<p>Hi everyone, and thanks for all the replies!<br>

It's a M645 1000s, so it has an electronically controlled shutter. However, I guess some of the lubrication of the mechanical parts has left the building, so there we go.<br>

The percentages I gave are pretty consistent: I measured 1s, 2s, 4s and 8s and it pretty much stayed at +20% for the one +50% for the other camera.<br>

Not sure if this would also be true fro the shorter times. I have actually seen some over-exposure on the 50% one, so I am wondering how to go about this.<br>

One way would be to use the next faster shutter speed, I guess...</p>

[rodeo_joe1]

<p>Florian, the old metal M645s are known for having shutter inaccuracies after a number of years. The issue is nothing to do with lubrication, but is apparently due to deterioration of components in the electronic circuit. IIRC it's down to a leaky electrolytic capacitor used as part of the timing circuitry. The circuit is fairly simple and basic and the component(s) can be fairly readily replaced - once access has been gained to it.</p>

<p>The camera comes apart fairly easily, but you have to strip the leathercloth off it, and this sometimes tears or distorts and won't go back tidily.</p>

<p>The repair manual can be viewed here:<br>

http://www.scribd.com/doc/35453483/Mamiya-M645-Service-Manual#scribd<br>

Electrical circuitry is shown from pp69 onwards. There is a variable resistor to adjust the shutter timing, but this would just be a fudge and the real fix is to replace the leaky timing capacitor C1. In fact it wouldn't hurt to replace both C1 and C2. The values don't appear to be given in the manual, but I'll bet they're just off-the-shelf components.</p>