M42 manual zoom

Hi all,
I've acquired a 35-100mm f3.5 zoom lens with M42 fitting.

I've disabled the auto mechanism and intend using it on my K10D.

Query --- What focal length should I put in when asked by the camera on switch on.

ie is it better to put in 100mm or say 70mm as being in the middle.


regards
Bernard

Has it got a "Your Guess is as Good as Mine" setting

I'd only bother if I was using 100mm in bad light, in which
case I'd set 100mm. 35mm should be OK without SR.

The best thing is probably test it at say 70mm at all FL's
I doubt if it will make much difference.

I thought that might be the answer, but it was worth the ask.

I wish all queries were as simple. I bogged down with a microsoft update that won't install (and won't go away either) MS put you onto a forum, which points you to a document on MS, which points to a forum, which.......


Thanks Algi

regards
Bernard

In theory you would need to enter the value you are using the lens at, just like any prime lens.

In practice I too would go for the middle ground unless I was using the lens at the longest length, for example to shoot wildlife.

Thanks John, I don't think wildlife are in danger from me using this lens (unless I drop it on a snail or something).

I suppose if I find a use for it at a particular focal length it's worth switching the camara off and back on again.


regards
Bernard

When I'm in the same situation I try to pick a focal length that I haven't already got that's somewhere near the middle. That way I can use the EXIF data to work out which lens it was (at least that's the theory).

Also remember not to pick something at the long end as at shorter focal lengths the camera will effectively overcompensate for that focal length and so still leave you with blur - setting it to 100mm correction but using it at 35mm will probably end up with more blur in the image that if you had turned it off

On pentaxforums.com, m42man posted a formula to calculate the 'optimal' value. You can search for posts by him.

Personally I will switch SR off.