Asashi Pentax Spotmatic SP shutter spring tensions.

Joosep · Joined: 25 Jan 2010 Posts: 305 Location: Estonia, Tallinn

Greetings from Estonia.

Ok. I got a Spotmatic SP and on 1/1000th and 1/500th the second curtain catches up to the first on. On 1/1000th exactly in the middle of the frame, on 1/500 in the end.
So, I hurd I have to open her up and give the springs some more tension.
Anyone done this ?

But my main question is...
Logically Ill give more tension only to the first courtain, right ?
But how will this effect the rest of the shutter speeds ?

Can someone who knows share his/hers knowledge.
Thanks Smile

rick_oleson · Posted: Fri Jul 02, 2010 2:55 am Post subject:

The curtain is probably slow because there is dirt in the mechanism. If you adjust the curtain tension to compensate for it, which you can do, it will not correct the cause of the problem and so it may not produce a satisfactory and consistent result. It would be best to have the shutter cleaned, and only make such adjustments to the spring tension as are necessary after you know it is properly cleaned and lubricated.

To your other question, making this adjustment to make 1/1000 and 1/500 come in correct will not greatly affect the slower speeds. You are making an adjustment of one or two thousandths of a second in curtain travel time. This is critical when your entire exposure is 1/1000, but when it is 4/1000 or 8/1000 (1/250 and 1/125), a variation of 1/1000 in one curtain does not greatly affect the exposure.

But in any case, the result will be better if you do the cleaning and lubrication first, and then (if it is still necessary) make any adjustments.