Pentax 165mm F/4 LS lens use

[jhnyguitar]

i recently purchased this lens used and have been trying to obtain an

owner's manual from pentax. according to them, they are completely

out of manuals for this lens. seems unbelievable, but i was contacted

by the voice of pentax herself with this answer to my inquiry so i

know this must be true. anyway, can anyone who has this lens and

accompanying manual give me some pointers on using it? i have the

90mm ls lens and know the differences between them and that the 165 ls

lens was made exclusively for strobe work, hence why i bought the

lens. i tried it the other day using the lens shutter @ 1/60 and the

body @ 1/30, thinking the slower shutter would give the lens shutter

time to fire. the resulting frame was blank. i noticed, though, that

there seemed to be a delay in the firing of the lens shutter, which

leads me to believe i must use a much slower shutter speed on the body

than on the lens. i guess my question is, what shutter speed does

pentax recommend using with the camera body when using the shutter in

this lens? if it were 1 sec., i could see how this would eliminate

any vibration caused by the shutter/mirror given the delay in the

firing of the lens shutter. any vibration would have ceased by the

time the lens shutter fires. however, i don't know whether 1 sec.

would be enough time. on my 90mm ls lens, i usually use it in special

mode and set the body shutter in between x and 1/1000. as you all

probably know, this point on the shutter dial keeps the shutter open

until the shutter dial is moved off of this point. i can't believe

this would be the same for the 165mm ls, given its design for

exclusive work with strobes. any suggestions/recommendations would be

helpful. thanks.

[art_haykin]

Just curious: in what way is that lens made exclusively for strobe work?

[leonardo 144]

Pentax advices to use 1/8 sec or slower. Pressing the shutter button or using the mirror lockup moves the attenuator that closes the diaphragm and, in the case of the`165, also starts the sequence of CLOSING the lens shutter and -after a certain amount of time (the focal plane shutter has to be fully opened)-opening and closing of the lens shutter and finally closing of the focal plane shutter.

Shorter times than 1/8 sec do not give the lens shutter enough time to excecute this chain of events.

Also, the 165LS is different from the 90LS in that the lens shutter can not be fired independently, only by the diaphragm attenuator, so MLU is not possible!

 

Hope this helps.