Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-16-2012, 04:40 AM   #1
Veteran Member




Join Date: Jan 2012
Location: NE, USA
Posts: 1,302
Leaf shutter lens

What is the purpose of the leaf shutter lens?

Is it for flash synch benefit only?

07-16-2012, 07:54 AM   #2
Senior Member
jase036's Avatar

Join Date: Mar 2010
Location: Calgary, Alberta
Photos: Gallery
Posts: 170
Leaf shutters have some problems at higher shutter speeds, as high speeds usually mean larger apertures required. This means that the shutter must open fully more rapidly, a severe burden on any mechanism. For this reason, shutter speeds on large format lenses are often limited to 1/500 second, or less (although there are some exceptions). The best optical location for a leaf shutter is the same as the aperture diaphragm, which creates more engineering problems.
There are some diffraction (minor) and relative aperture phemomena noted at high shutter speeds, in that the shutter's aperture becomes the lens aperture that is constantly changing from f/inf to f/min and back.
Also as the shutter assembly ages, the shutter speed decreases, so you might be dialing in 1/500 when in fact the shutter speed is 1/320.
I would say that it would have to be really important for the photographer to have high sync speeds at any power setting to justify the extra expense and lower maximum shutter speeds. I say at any power setting because most dedicated flash systems can sync at any speed using reduced power or rapidly strobing pulses.
07-16-2012, 11:14 AM   #3
Senior Member
klaus123's Avatar

Join Date: Apr 2011
Location: Germany
Posts: 205
I think for old analog MF-Cameras with low sync-speeds (6x7 = 1/40) LF-Lenses are the only chance for daylight fill flashes.
I made some tries with a lend 75LS on my 645 and found that the real benefit is visibal only if the exposure difference between ambient exposure and flash exposure is less the 2 F-stops - if the difference is bigger (flash lighter) ghost pictures by camera movements are neglligable.

Link to this test (sorry in German): http://forum.digitalfotonetz.de/download.php?id=23758

After this tests I decided to buy a 90LS which I can use on 645 & 67 - ans since than never used it for flash photos

On the 67 I hoped that the handheld pictures at slow speed might be better (less vibration at the time of exposure) - but since now I have not been able to verify it

Last edited by klaus123; 07-16-2012 at 11:22 AM.
07-17-2012, 11:44 PM   #4
Veteran Member
Silent Street's Avatar

Join Date: Nov 2011
Location: Snobsville & Hipsterville, Vic AUS
Posts: 445
Flash sync (studio flash, chiefly) at higher speeds rather than the 1/30 standard sync on the 67 / 6x7 bodies is the chief selling point. LS lenses (Pentax makes only the 165mm LS now) are also considerably heavier than non-LS lenses due to the additional shutter mechanics in the design, and they require careful setting up when actually used in leaf-shutter mode (that is to say, they are not full-time leaf shutter lenses, but are selectable/de-selectable and a procedure must be followed to avoid damage to the lens or the camera). Camera-side shutter speed must be set to 1/15 in leaf-shutter mode. The ancient (1971) 90mm 2.8 LS has the interesting feature of being able to trigger the 67/6x7 body independently for vibration-free shots; this cannot be done with the bigger (heavier) 165mm LS lens. And that (165mm) requires solid stability to avoid introducing vibration, so MLU is a must for it unless using very high speed film and correspondingly higher (>1/250)Tv values. Performance-wise neither lens is as stellar as a number of other SMC lenses in the Pentax stable. My personal go-to favourite is the 55mm f4.


Last edited by Silent Street; 07-17-2012 at 11:59 PM. Reason: 2x typos
07-18-2012, 12:20 PM   #5
Pentaxian




Join Date: Jul 2009
Location: Seattle
Posts: 6,929
The manual for the P6x7 LS lenses says set the body to 1/8th shutter speed (or slower) to use the LS feature.

The 90mm LS in pure leaf shutter mode doesn't do anything to "trigger" the P6x7 body. You lock the shutter open on the body manually with that special (hidden) mode between X-sync and 1/1000th on the dial (press the shutter button and it locks open), arm the leaf shutter and fire with a cable release connected to the lens. You have to now close the camera's shutter manually by taking it off the locked open position or arm the leaf shutter and shoot again for multiple exposures.

Last edited by tuco; 07-18-2012 at 12:43 PM.
08-04-2012, 04:54 PM   #6
Site Supporter




Join Date: Nov 2011
Location: pontiac mi.
Posts: 339
useing a ls lens is not that complicated.ok, set the camera to manual and the apature to f.8. attatch the flash to the shoe, and the sync cord to the lens. then set the lens for shutter speed ,and the apature for distance.experiment until you get the hang of it.
08-04-2012, 11:56 PM   #7
Senior Member
klaus123's Avatar

Join Date: Apr 2011
Location: Germany
Posts: 205
Finding right exposure is not that difficult - either use the old, flshintegrated A-mode or make test shots with a dslr (if you do not own a flash-meter)
This is like w/o LS-Lens for all cameras w/o P-TTL.
08-05-2012, 04:43 AM   #8
Site Supporter




Join Date: Nov 2011
Location: pontiac mi.
Posts: 339
QuoteOriginally posted by klaus123 Quote
Finding right exposure is not that difficult - either use the old, flshintegrated A-mode or make test shots with a dslr (if you do not own a flash-meter)
This is like w/o LS-Lens for all cameras w/o P-TTL.

setting the shutter speed to 1/500 sec,and useing the iso/ distance scale to figure apature puts me in the ball park.

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, leaf, leaf shutter, lens, medium format, shutter
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Could/should Pentax ever make a new leaf shutter lens? TomTextura Pentax SLR Lens Discussion 4 06-12-2012 08:48 AM
Dum leaf shutter lens question kenyee Pentax Medium Format 5 02-02-2011 03:42 PM
Thoughts on 90mm leaf shutter lens Isis Pentax Medium Format 4 09-21-2010 03:44 AM
K7 and the 75mm Leaf Shutter Lens HawaiianOnline Pentax Medium Format 4 09-20-2010 10:12 AM
165mm leaf shutter lens for 67 Ade-oh Pentax Medium Format 6 12-30-2009 12:02 PM



All times are GMT -7. The time now is 03:50 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top