Pentax 645 LS 135mm f/4.0

Wanting to get a portrait lens, I bought a Pentax 645 LS 135mm f/4.0 LS a while ago to complement my use with the Pentax 645N. And what appeals me most is the use of leaf shutter. According to PDF documentation on leaf shutter in PentaxImaging, the built in leaf shutter on the lens won't work on 35mm full frame bodies with the 645 K adapter. It was my wishful thinking that the leaf shutter might magically work on Pentax digital which has its limitation on 1/180 sec. synch speed.

Pentax 645 LS 135mm f/4.0
Pentax 645 LS 135mm f/4.0
The lens has a LS setting for 60, 125, 250 and 500 on the lens front. Once engaged in LS setting, one has to cock the LS ring for each shot; otherwise, the curtain will be down and not flip up upon shutter release.

I learn it from other experienced user that the timing of the sync on the body terminal is with the focal plane shutter on the body which is not the same sync timing as the one on the lens. That is why there is a sync terminal(PC socket) on the lens to sync flashes when the lens shutter is in use. There is an accessory which is a hot shoe with a sync cable - the shoe goes into the camera and the sync socket into the lens.

Though I have not used any flash with the lens, the LS lens won't work in TTL mode like other 645 A lens. When leaf shutter is used, I do need to get two accessories like a hot shoe and a sync cable to connect between the hot shoe and the sync contact on the lens. I will go about finding these two items in eBay for future trial

Here are few test shots that I did a while ago with Pentax 645N and Kodak Tri-X 400

Pentax 645 LS 135mm f/4.0

Pentax 645 LS 135mm f/4.0

Pentax 645 LS 135mm f/4.0

Pentax 645 LS 135mm f/4.0

Impressions & Notes
  • The lens has surprising performance for me when I use it like a regular non-LS lens.

  • I like the handling and small size of this leaf shutter lens. It is not much bigger than the A 75mm f/2.8

  • It is a good addition when I want to pair this lens with the the 75mm and use this longer focal length for portrait and candid.

  • I currently don't have the accessories to try out the leaf shutter with a flash. I have been spoiled by digital with instant feedback on flash pictures and easier correction in re-shooting. I doubt I will have a easier time to work without TTL and that I have to use all manual setting on the flash and the lens leaf shutter setting. It is a challenge to be planned and worked out for next report.



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