SMC Pentax 645 LS 1:4 135mm

– Attach the SMC Pentax 645 LS 1:4 135mm the usual way to your Pentax 645D.
– When selecting the shutterspeed on the lens (front ring) leaf shutter operation is automatically engaged on the body, it displays “LS” on the screen.
– Available shutterspeeds: 1/60, 1/125, 1/250 and 1/500.
– The lens also has a setting of “0”, which doesn’t use the leaf shutter (it becomes a normal 135mm f/4 for the Pentax 645 system).
– Attach your flash (trigger) to the standard PC connector on the LS 1:4 135mm.
– Aperture is automatic, like with all Pentax-A lenses (no stop down metering necessary).
– Remember to cock (wind-up) the shutter after each photo, you do this by turning the ring just behind the shutterspeed ring on the lens.
– The shutter is cocked when you can see through the viewfinder. After you take a photo the viewfinder remains dark indicating that the shutter has fired and has to be cocked again.
– There is some delay after pressing the shutter-release button before the Pentax takes the photograph.
– Mirror lockup doesn’t work with leaf shutter operation (no biggie).

Pentax 645D with SMC 645 LS 135mm
Pentax 645D with SMC 645 LS 1:4 135mm (shot with iPhone)

Using a leaf shutter lens has been a long-time wish of mine because it enables you to use flash on all speeds, so you can use faster shutterspeeds (usually up to 1/500 to 1/800) than the x-sync speed of your camera, blocking out daylight and / or freezing action or even slight movements better. For the Canon system I owned before there are no leaf shutter lenses. To this day I don’t understand why Canon won’t make a couple, for example a 40 f/4 and 80 f/4 with leaf shutter operation up to 1/800 second or even 1/1000. Or maybe a 35 f/4, 75 f/4 and 150 f/5.6. Even Pentax doesn’t make them anymore, but they used to and when I decided to get the 645D (even before I actually got it) I managed to scare up an SMC 645 LS f/4 135mm in mint condition on Ebay. I had some doubts as to whether it would work perfectly on the 645D but fortunately it does, just attach it and everything works automatically.

To test it I set up a couple of shots with Annette in a beautiful apartment in Rotterdam, where the 1/500 flash synchronisation the leafshutter in it provides would be somewhat benificial, to block most of the natural light and create the mood with flash only. I used my Aurora Fusion studio flashlight, connected with an extended pc-sync cord to the LS 135 f/4. I fear my triggers aren’t fast enough for 1/500 second so I didn’t use them. I will test that later.



Of course the SMC Pentax 645 LS 1:4 135mm is manual focus only but since I always use MF anyway that isn’t a problem for me. The sharpness and overall quality (lack of artifacts) is excellent, even compared to the 90 f/2.8 macro I own. Maybe it’s slightly less sharp (it better be, considering the price of the 90 f/2.8) but I’m sure that will go completely unnoticed under normal circumstances. This will be my preferred fashion-lens for sure. I’m already setting up another shoot because I want to use it so bad.

5 thoughts on “SMC Pentax 645 LS 1:4 135mm”

  1. Hi! I also have the Pentax 645d and def. need a leaf shutter lens, wish they made new ones that synced faster but — have you tried them with a pocket wizard yet, thanks for your time!

    1. You can use HSS now, with Godox trigger and strobes. I recommend the Godox X2T-P tigger and the AD200 Strobe or the Ad300 or Ad400 Pro.

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