Pages: [1]   Go Down

Author Topic: Phase One P65+ article  (Read 4545 times)

marcmccalmont

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1780
Phase One P65+ article
« on: March 13, 2009, 07:08:28 pm »

Michael
1. When I use a manual lens on my Mamiya 645 AFDII pressing the AEL button will automatically set the correct exposure by adjusting the shutter speed, I would be surprised if the Phase One AFD III did not have the same function. My technique is to open up the lens, focus, stop down the lens, press [AEL], shoot. easy!
2. I built a vibration isolation device, mounted between the tripod and ball head. A fair amount of the camera vibrations that travel down the head/tripod can be damped before they are reflected back, the vibrations are damped in a fraction of a second instead of seconds. The downside is the head is mounted on a fluid coupling and framing is a bit awkward.
[attachment=12132:IMG_0426.jpg]
« Last Edit: March 13, 2009, 08:20:25 pm by marcmccalmont »
Logged
Marc McCalmont

Bill Caulfeild-Browne

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 313
    • http://www.billcaulfeild-browne.com
Phase One P65+ article
« Reply #1 on: March 13, 2009, 09:38:06 pm »

I have much the same gear as Michael, only with the P45+. I too have had vibration problems with the 300 mm APO lens.

Here are my findings and partial solutions.

MLU is fine, but even waiting 5-10 seconds doesn't always help. The reason, I've concluded, is the focal plane shutter. Every action has an equal and opposite reaction, and it's that reaction that causes blurring. (I confirmed this by attaching a small mirror to the lens and watching the reflection of a flashlight beam over many feet in a dark room as I operated the shutter with MLU - the rig amplifies any motion.)

Holding the camera on a rock-solid brick wall solves the problem, but the brick wall is very hard to carry around. But no question, the more inertia in one's tripod, the better.

I found the problem worse when using the lens mounted to the tripod, which is logical. It balances the camera equally fore and aft, which more readily permits a see-saw movement when the shutter moves. By losing the tripod lens mount and using the camera mounted directly on the tripod, then there is a lot of mass at the far end of the lens which is harder to lever into movement. (Overall, the 300 is a very light lens - I'd rather it were heavier! I may try draping a sandbag over the lens.)

Shutter speeds from 1/100th and faster are generally fine. This is less of a problem than you might think because the lens is optimally sharp at full aperture anyway. Speeds longer than 1 second look good too. One needs to avoid 1/2 to 1/1/60th sec. A pain! In practice. I tend to up the ISO and try for at least 1/250th sec.

I do not have this problem with any other lens. I think the 75-150 has so much mass it keeps things immobile.

I hope this may help others and I'd be glad to hear others' recommendations.

Bill
Logged

michael

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 5084
Phase One P65+ article
« Reply #2 on: March 14, 2009, 09:11:21 am »

Bill, you're absolutely right about the problem with long lenses on the 645 being vibration from the focal plane shutter. That was my surmise since I never had such problems with the Hassy H2 and 300mm since it has a leaf shutter.

I've just started working with a Arca Cube head (which I bought after working with Mark D's in Zion) and its extra rigidity over the RRS head seems to make a bit of a difference.

With the better high ISO capability of the P65+ I'm now simply going to keep my exposure shorter when using the 300 and 500mm.

M
Logged

method

  • Newbie
  • *
  • Offline Offline
  • Posts: 40
    • http://www.method-photo.co.uk
Phase One P65+ article
« Reply #3 on: March 14, 2009, 10:06:12 am »

Just to say, this was a fascinating article. I will probably never own or use one of the cameras, but it sounds amazing and the photos do have a depth about them that makes them stand out - even on the web.
Logged

marcmccalmont

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1780
Phase One P65+ article
« Reply #4 on: March 14, 2009, 10:51:09 am »

Quote from: michael
Bill, you're absolutely right about the problem with long lenses on the 645 being vibration from the focal plane shutter. That was my surmise since I never had such problems with the Hassy H2 and 300mm since it has a leaf shutter.

I've just started working with a Arca Cube head (which I bought after working with Mark D's in Zion) and its extra rigidity over the RRS head seems to make a bit of a difference.

With the better high ISO capability of the P65+ I'm now simply going to keep my exposure shorter when using the 300 and 500mm.

M

Can you diagnose the problem a bit further? Perhaps a bean bag on the lens and then a bean bag on top of the camera to see where the problem is? I found a hand on the top of the camera or the vibration isolation device solved the problem for me. I then assumed the vibration was from the shutter.
Marc
Logged
Marc McCalmont

JRSmit

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 922
    • Jan R. Smit Fine Art Printing Specialist
Phase One P65+ article
« Reply #5 on: March 17, 2009, 03:51:09 am »

Quote from: marcmccalmont
Can you diagnose the problem a bit further? Perhaps a bean bag on the lens and then a bean bag on top of the camera to see where the problem is? I found a hand on the top of the camera or the vibration isolation device solved the problem for me. I then assumed the vibration was from the shutter.
Marc
From remarks in this thread it looks to me as the primary resonances (eigenfrequencies) of the system(camera + tripod), in the range of 10 - 60 herz. One can measure these with an accelerometer or similar connected to a computer with the right software to analyse the vibrations and see if alternatives can reduce the problem. But do not expect a significant solution as the tripod with its lengthy legs will always have some vibration in that range. Adding mass directly to the body with the focal plane shutter is a good way to reduce the vibration amplitude, provided it is as close as possible to the source and as ridgid as possible.

IQ is technology, PQ is YOU

Jan R.
Logged
Fine art photography: janrsmit.com
Fine Art Printing Specialist: www.fineartprintingspecialist.nl


Jan R. Smit

marcmccalmont

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1780
Phase One P65+ article
« Reply #6 on: March 17, 2009, 11:35:28 am »

Quote from: JRSmit
From remarks in this thread it looks to me as the primary resonances (eigenfrequencies) of the system(camera + tripod), in the range of 10 - 60 herz. One can measure these with an accelerometer or similar connected to a computer with the right software to analyse the vibrations and see if alternatives can reduce the problem. But do not expect a significant solution as the tripod with its lengthy legs will always have some vibration in that range. Adding mass directly to the body with the focal plane shutter is a good way to reduce the vibration amplitude, provided it is as close as possible to the source and as ridgid as possible.

IQ is technology, PQ is YOU

Jan R.

A very good reason to de-couple the camera from the legs with a vibration isolation device! I might invest in an accelerometer, I already have several audio frequency spectrum analyzers that are compatible with accelerometers.
Marc
Logged
Marc McCalmont

JRSmit

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 922
    • Jan R. Smit Fine Art Printing Specialist
Phase One P65+ article
« Reply #7 on: March 17, 2009, 04:35:54 pm »

Quote from: marcmccalmont
A very good reason to de-couple the camera from the legs with a vibration isolation device! I might invest in an accelerometer, I already have several audio frequency spectrum analyzers that are compatible with accelerometers.
Marc
Using mass to absorb energy thus reducing amplitude is totally different from isolating. Isolation devices are usually some kind of spring action with more or less significant dmping. As such can, thus will, introduce its own resonance(s). However above its resonance frequency it will isolate(not pass through) vibrations, like your car's suspension. So in essence some mass attached ridgindly to the camerabody with some damped isolation could work, but give a wobbly aiming of the camera itself.
Other forums report a frequency range coming from the legs of around 1/15 second ie ~6 herz. Not a cheap accelerometer to cover that frequency range, but worth a try. Yes with audio spectrum analysers this can be easily accomplished.

IQ is Technolgy, PQ is YOU

Jan R.
Logged
Fine art photography: janrsmit.com
Fine Art Printing Specialist: www.fineartprintingspecialist.nl


Jan R. Smit

marcmccalmont

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1780
Phase One P65+ article
« Reply #8 on: March 17, 2009, 05:56:32 pm »

Quote from: JRSmit
Using mass to absorb energy thus reducing amplitude is totally different from isolating. Isolation devices are usually some kind of spring action with more or less significant dmping. As such can, thus will, introduce its own resonance(s). However above its resonance frequency it will isolate(not pass through) vibrations, like your car's suspension. So in essence some mass attached ridgindly to the camerabody with some damped isolation could work, but give a wobbly aiming of the camera itself.
Other forums report a frequency range coming from the legs of around 1/15 second ie ~6 herz. Not a cheap accelerometer to cover that frequency range, but worth a try. Yes with audio spectrum analysers this can be easily accomplished.

IQ is Technolgy, PQ is YOU

Jan R.

Actually these isolators are dampers and can be tuned for various frequencies (by size and loading), they were designed to keep motors quiet on US attack subs, and are very efficient at converting energy, they do not bounce when dropped! Constrained layer damping is much more efficient than mass damping and could be used by manufacturers inside the camera.  When designing loudspeakers I de-couple them from the floor with proper vibration isolation feet, it seems to me de-coupling the camera from the tripod needs more exploration. My quick tests with a 645 AFD II/P30 showed equal improvement by either a hand on top of the camera or my "Vibration Isolation Device". Thanks for the 6 to 15 hertz target range, when isolating audio equipment I shoot for about 10 Hz (1/2 of 20hz) for this application would you tune to 7.5 hz (1/2 of the 15 hz resonance)?
Marc
Logged
Marc McCalmont
Pages: [1]   Go Up