[hinman]

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Wanting to get a portrait lens, I bought a Pentax 645 135mm f/4.0 LS. And a few shots to show the lens

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.

1. Do anyone have experience with LS lens?

2. I assume that I don't need any sync cable to join the lens and the camera if I use a TTL flash as in AF280FT in TTL mode off the hot shoe. Is that correct?

3. If I purchase a 645 to K mount adapter, will the LS continue to work on K-mount digital bodies? Wishful thinking, but I really have no idea.

4. Anyone with the other LS lens as in 75mm f/2.8 LS and this lens with 135mm f/4.0 LS?

Thanks,
Hin

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Last edited by hinman; 11-12-2010 at 09:36 PM.

[drougge]

1. Unfortunately I don't.

2. I would expect you need to connect the flash to the lens. Unless I misunderstand the operation, it goes like this: You press the shutter button. The camera pushes the aperture lever on the lens. The lens closes the leaf shutter, stops down the aperture and starts a timer. The camera opens the focal plane shutter. The camera will now fire the flash, uselessly. The timer in the lens triggers the leaf shutter. And then the obvious close down from this. If the flash is connected to the lens, it will trigger at the right moment. (But you don't get TTL metering for it, obviously.)

3. Unlikely, as the adapter never pushes the aperture lever. You could probably modify it so you could trigger it manually, and use pretty long exposures on the camera side. But it would be even less convenient than usual operation with the lens.

[kenyee]

I didn't know that's how the LS worked...weird to see a PC sync port on a lens... :-)

[tuco]

I have 67 LS lenses. And I'd have to read the manual for the 645 but I'd suspect the hot shoe on the camera body is going to trip the flash at the sync of the camera not the LS. You'd need a hot shoe adapter that slips on the camera's shoe with a cord that connects to the lens's sync socket.

[hinman]

..
2. I would expect you need to connect the flash to the lens. Unless I misunderstand the operation, it goes like this: You press the shutter button. The camera pushes the aperture lever on the lens. The lens closes the leaf shutter, stops down the aperture and starts a timer. The camera opens the focal plane shutter. The camera will now fire the flash, uselessly. The timer in the lens triggers the leaf shutter. And then the obvious close down from this. If the flash is connected to the lens, it will trigger at the right moment. (But you don't get TTL metering for it, obviously.)

3. Unlikely, as the adapter never pushes the aperture lever. You could probably modify it so you could trigger it manually, and use pretty long exposures on the camera side. But it would be even less convenient than usual operation with the lens.

I have 67 LS lenses. And I'd have to read the manual for the 645 but I'd suspect the hot shoe on the camera body is going to trip the flash at the sync of the camera not the LS. You'd need a hot shoe adapter that slips on the camera's shoe with a cord that connects to the lens's sync socket.

Thank you all for the inputs. I think Tuco and Drougge are correct in needing the sync cable between the flash and the lens as the flash need to be in sync with the leaf shutter speed on the lens and not the shutter speed in the camera. I read somewhere that the camera shutter plane will be set to 1/8 of a second.

I saw the PDF documentation on leaf shutter in PentaxImaging. The built in leaf shutter on the lens won't work on 35mm with the 645 K adapter.

And with the 645 K adapter, my 135mm f/4.0 LS can only be used in non-LS mode. For other 645 'A' lens, 'A' aperture won't be supported and the lens need to be stop-down with aperture in M mode.

I will hopefully report back when I can test it with a sync cable.

Thanks,
Hin

[D W]

1. Do anyone have experience with LS lens?
Yes

2. I assume that I don't need any sync cable to join the lens and the camera if I use a TTL flash as in AF280FT in TTL mode off the hot shoe. Is that correct?
NO, 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.
You will not be able to use the TTL sensor in the camera. But I found the Quantum sensor (QF51) works quite well for flash exposures on the camera shoe.

3. If I purchase a 645 to K mount adapter, will the LS continue to work on K-mount digital bodies? Wishful thinking, but I really have no idea.
NO there is no mechanical linkage on the 645 lens to K body adapter. It is the aperture stop down mechanism which stops close the shutter in the lens, stop the lens down and opens the shutter for exposure. BTW for anyone who is curious, the 75LS seemed to work on the 645D.

4. Anyone with the other LS lens as in 75mm f/2.8 LS and this lens with 135mm f/4.0 LS?
ME

Thanks,
Hin

Answering as a 20+ yrs pro user of the 75LS and 135 LS.

[wkkato]

I may be all wrong here but I thought that the 75LS and 135LS worked just like a regular manual focus automatic diaphragm lens if you didn't cock the shutter. If this is true, then you should be able to sync the flash to the camera from the sync speed of 1/60 and slower. With the LS you have 1/60 and faster. That's why there is no slow speed shutter train in the LS lens--not needed.

[D W]

I may be all wrong here but I thought that the 75LS and 135LS worked just like a regular manual focus automatic diaphragm lens if you didn't cock the shutter. If this is true, then you should be able to sync the flash to the camera from the sync speed of 1/60 and slower. With the LS you have 1/60 and faster. That's why there is no slow speed shutter train in the LS lens--not needed.

Yes for shutter speeds slower than 1/60 there is no need to use the leaf shutter. The flash is then sync to the body shutter.

The need to sync to the camera's shutter is when that is used.

[kenyee]

Answering as a 20+ yrs pro user of the 75LS and 135 LS.

Thanks for testing this...I've been wondering...

[hinman]

Thank you all for all the valuable inputs. I saw another threads asking about the LS and I want to bump this thread so as to share the inputs from real user experience such as those from D_W and Tuco

I am yet to get the sync cable and the hot shoe adapter. I have these two items in my watch list in ebay, can someone confirm me if those are the two correct items to purchase:

• Camera&Flash PC Sync Cord/Cable Fu Ji S5PRO Pentax 20D? - eBay (item 170552185392 end time Dec-12-10 02:20:13 PST) -- PC sync cable
• ---
• Hot Shoe PC Sync Camera Flash Adapter f/ Pentax Olympus - eBay (item 250668532326 end time Dec-15-10 07:24:52 PST) -- Hot shoe adapter

It seems to me that the feature becomes less usable when using the LS will lose the TTL metering. Also another question is that in LS mode, does the camera autmatically set the shutter to 1/8 sec for the focal plane shutter while the lens shutter is set manually to one of the settings. When I cock the LS to one of the 60, 120, 250, 500 setting, the viewfinder displays the "LS" setting for shutter speed. Hence, I am guessing that the camera in 645N knows to shutter at 1/8 sec.

Thanks,
Hin

[hinman]

I have tried out the LS lens as a regular lens and it works alrgiht. Wide open in f/4.0 and f/5.6 seems to be a touch soft; otherwise, the lens is quite usable.

All test pictures shot with Kodak Tri-x 400, Pentax 645N, 135mm LS f/4.0, scanned at home with Canon 8800F.

My scanning at home don't match well with the actual pictures, it is still an on-going and frustrating process. When I developed the pictures in darkroom with 8x10 Ilford Pearl papers, they do come out with more detail, better tone, and sharpness than my own amateurish scanning.

Thanks,
Hin

[D W]

Thank you all for all the valuable inputs. I saw another threads asking about the LS and I want to bump this thread so as to share the inputs from real user experience such as those from D_W and Tuco

I am yet to get the sync cable and the hot shoe adapter. I have these two items in my watch list in ebay, can someone confirm me if those are the two correct items to purchase:

• Camera&Flash PC Sync Cord/Cable Fu Ji S5PRO Pentax 20D? - eBay (item 170552185392 end time Dec-12-10 02:20:13 PST) -- PC sync cable
• ---
• Hot Shoe PC Sync Camera Flash Adapter f/ Pentax Olympus - eBay (item 250668532326 end time Dec-15-10 07:24:52 PST) -- Hot shoe adapter

It seems to me that the feature becomes less usable when using the LS will lose the TTL metering. Also another question is that in LS mode, does the camera autmatically set the shutter to 1/8 sec for the focal plane shutter while the lens shutter is set manually to one of the settings. When I cock the LS to one of the 60, 120, 250, 500 setting, the viewfinder displays the "LS" setting for shutter speed. Hence, I am guessing that the camera in 645N knows to shutter at 1/8 sec.

Thanks,
Hin

The original Pentax unit has a shoe which has no contact at the bottom with a hot shoe mount on the top. There is a short, about 6-8 inches coiled pigtail pc cord which fits into the sync socket on the lens.
That is the best as far as a description is concern. I am not near that piece of equipment right now and will probably be next Jan when I can get a photo of it.