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Photo Forum / Digital Photography / DSLR Cameras / February 2006DSLR better for manual focus than P/S at night?
Hi Everyone, I've been struggling a bit with pushing my P/S digital (Panasonic FZ30) to long exposures at maximum zoom at night, taking 30-60 second exposures at 420 mm. My photographic objectives are typically 4-5 miles away, across a body of water, and, when I view the structures I'm photographing with the naked eye, the lights anchored to them (blast furnaces, factory buildings, etc) are shimmering/twinkling pretty badly. I'm using manual focus, but my results are mixed, and I frequently come home with 2/3 of my pictures looking blurry, even though I'm focusing as tightly as possible using the lcd display screen on the camera. I'm using a sturdy tripod, plus a cable shutter release. I also let the tripod/camera "settle" for at least 30 seconds before starting an exposure. I've fixed the ISO at its minimum value, and I'm working about two stops short of minimum f-ratio. When I perform the manual focus, I'm iterating several times until the image I'm viewing is as in focus as I can achieve in my limited experience, so I'm wondering if I'm doing anything wrong, or if the camera and atmospheric conditions are killing my focus. Some of my shots turn out pretty good, taken only several minutes apart from unfocused shots, so I don't think it's the camera or the atmospheric conditions (especially with water evaporation on the bay between me and the buildings, nearly 3 miles wide, with me shooting from the beach, so I'm at sea level). My question is, can a DSLR offer more precise manual focus? For example, how about the Nikon D70 or D200? How does one perform a manual focus with these cameras? Is one using an lcd display screen, as I would do with the FZ30? I realize, with the FZ30, I'm viewing the live image on the main camera sensor, which wouldn't be the case with a DSLR. So how is manual focus done with a DSLR, and would it be easier to achieve tighter focus with such a camera, at, say, 400 mm zoom, than with my FZ30? Thanks for any help, Scott Speck >Hi Everyone, > [quoted text clipped - 4 lines] >naked eye, the lights anchored to them (blast furnaces, factory buildings, >etc) are shimmering/twinkling pretty badly. That will cause your photographs to be blurred unless the exposure is much less than the time it takes air-cells to move in the path. >I'm using manual focus, but my >results are mixed, and I frequently come home with 2/3 of my pictures >looking blurry, even though I'm focusing as tightly as possible using the >lcd display screen on the camera. It is the same as the stellar scintillation (twinkle) effect with stars. >My question is, can a DSLR >offer more precise manual focus? Yes, but focus is not the issue, you told us that it is "shimmering/twinkling pretty badly". >For example, how about the Nikon D70 or >D200? How does one perform a manual focus with these cameras? Look through the viewfinder. >Is one using >an lcd display screen, No, the LCD is for reviewing the photograph after taking it, only one DSLR about to hit the shops offers live LCD preview; from comments made the viewfinders are variously dim or slow updating which would probably make it unsuitable for your application. >as I would do with the FZ30? I realize, with the >FZ30, I'm viewing the live image on the main camera sensor, which wouldn't >be the case with a DSLR. Whilst you are not viewing the image that is on the sensor (it's covered by the shutter) you are viewing the image that will be on the sensor when the shutter opens (I am ignoring subject movement). >So how is manual focus done with a DSLR, and would >it be easier to achieve tighter focus with such a camera, at, say, 400 mm >zoom, than with my FZ30? Should be.  SignatureIan G8ILZ > Hi Everyone, > [quoted text clipped - 28 lines] > Thanks for any help, > Scott Speck Just my two cents: Since what you are shooting is miles away, every shot is going to be at infinity, so I'm not sure focus is the problem. It sounds more like some atmospheric interference or camera movement, depending on the shutter speeds you are using. A DSLR can offer you better lenses, faster lenses, and options that may get you better photos, but don't expect a miracle. If, as you say, 1/3rd of your photos are good, those are pretty good numbers for any photographer. It would probably be easier to diagnose the problem if we could see the images, both good and bad. Thanks for your thoughts. The problem with my camera is FINDING infinite focus. The manual focus ring doesn't have a physical "stop" at infinity, and I can keep rotating the ring beyond infinity, creating a cyclical focal behavior. -Scott >> Hi Everyone, >> [quoted text clipped - 40 lines] > photographer. It would probably be easier to diagnose the problem if we > could see the images, both good and bad. >Thanks for your thoughts. The problem with my camera is FINDING infinite >focus. The manual focus ring doesn't have a physical "stop" at infinity, >and I can keep rotating the ring beyond infinity, creating a cyclical focal >behavior. So take a bit of time with your camera mounted on a tripod to find where infinity focus is through trial and error and make a mark on the ring. SignatureEd Ruf Lifetime AMA# 344007 (Usenet2@EdwardG.Ruf.com) See images taken with my CP-990/5700 & D70 at http://edwardgruf.com/Digital_Photography/General/index.html Thanks Ed, I'm going to try that. I hope this works, since the manual focus ring is, from what I know, electronically coupled to the camera, not mechanically. So hopefully, if I make the mark at the correct spot, turn the camera off, then on, spin the ring a few times, and then align the mark, it will actually return to the same physical focus on the camera detector as had previously been the case. I have another question for you, too. If I set the focus at infinity, should the image remain in focus as a function of zoom? Thanks, Scott >>Thanks for your thoughts. The problem with my camera is FINDING infinite >>focus. The manual focus ring doesn't have a physical "stop" at infinity, [quoted text clipped - 4 lines] > So take a bit of time with your camera mounted on a tripod to find where > infinity focus is through trial and error and make a mark on the ring. >Thanks Ed, I'm going to try that. I hope this works, since the manual focus >ring is, from what I know, electronically coupled to the camera, not [quoted text clipped - 5 lines] >I have another question for you, too. If I set the focus at infinity, >should the image remain in focus as a function of zoom? Depends on the lens design. You could try asking tech support or try it yourself at the extreme ends of the zoom. SignatureEd Ruf Lifetime AMA# 344007 (Usenet2@EdwardG.Ruf.com) See images taken with my CP-990/5700 & D70 at http://edwardgruf.com/Digital_Photography/General/index.html Ed, I think I've figured out what to do, because the manual focus ring is not hard-coupled to the focusing process. For example, if I set the ring to achieve proper manual focus at infinity, then switch to autofocus and focus on something closeby, the manual focus ring doesn't move during the autofocus process. As a result, if I then switch BACK to manual focus, I'm out of focus for infinity, but my focus ring is still at the original position that allowed the camera to BE at focus at infinity. I've therefore figured out a couple options that should work, and I'll test them tonight: 1) Autofocus the camera on a distant object (infinity) during the day, when the camera's AF is really good at locking a nice sharp focus. Then, switch to manual focus and don't touch (or somehow anchor) the manual focus ring from being able to turn. When I re-power the camera in manual focus, it'll still be set at infinity. 2) my camera has a "starry sky mode", which, I believe causes the camera to move to infinite focus. I could take a frame (in AF mode) in starry sky mode, and then switch out of starry sky and back to manual focus. Then I would refrain from touching the manual focus ring. I should stay at infinity, in this case. This might be better than option 1, since I could re-achieve infinite focus in low light even if I accidentally moved the manual focus ring (as might happen with method 1). I also switched OFF anti-shake, since the manual warns AGAINST using anti-shake for long exposures. I thinks this might have been causing some of the bizarre optical effects I was seeing (not just being out of focus, but bizarre "doubling" or "tripling" of some images, despite no camera motion). I'll keep ISO at 80 (minimum). With all of this in place, I think I'll be able to get better results. Thanks again, Scott ----- Original Message ----- From: "Ed Ruf (REPLY to E-MAIL IN SIG!)" <egruf_usenet2@cox.net> Newsgroups: rec.photo.digital.slr-systems Sent: Sunday, February 05, 2006 10:14 AM Subject: Re: DSLR better for manual focus than P/S at night? >>Thanks Ed, I'm going to try that. I hope this works, since the manual >>focus [quoted text clipped - 11 lines] > Depends on the lens design. You could try asking tech support or try it > yourself at the extreme ends of the zoom. >Thanks for your thoughts. The problem with my camera is FINDING infinite >focus. The manual focus ring doesn't have a physical "stop" at infinity, >and I can keep rotating the ring beyond infinity, creating a cyclical focal >behavior. >-Scott You are likely to find it difficult under certain circumstances solely owing to atmospheric (air density) changes. At 400mm, you are in essense magnifying the turbulence by about 8x relative to what your eye sees. That rippling effect above a BBQ you see with your eyes is what telephoto lenses make more apparent. The larger the front element of the telephoto lens (assuming you are using it wide open) the greater the problem. Magnification makes it more apparent as well. This is why (especially in daytime due to heatwaves) you are limited in the amount of detail that any lens can show over long distances where the air blanket and irregularies are deep. This is also why testing lenses over long distances is problematic. The steadiest conditions unfortunately coincide with things like high moisture content and fog which themselves attenuate detail at distance. -Rich > Thanks for your thoughts. The problem with my camera is FINDING infinite > focus. The manual focus ring doesn't have a physical "stop" at infinity, > and I can keep rotating the ring beyond infinity, creating a cyclical > focal behavior. > -Scott My camera is like this. There should be an infinity symbol on the focus ring. The problem is that some manufactuturers have found that because of zoom and temperature issues they can no longer put a stop at infinity, so it leaves you having to find it yourself. I just use the symbol, and unless you are shooting wide open, if you stop down a couple of stops you should be well in the ball park. As a matter of fact, if you are not using a 1.8 or 2.8 lens wide open, just using that infinity symbol should be enough. Personally, I hate the focus rings on most autofocus lenses. The manufacturer's forgot that many of us still like to shoot in manual mode now and then. This is where a DSLR might pay off, as you can use lenses made for 35mm cameras with all the manual controls that go along with them. > value, and I'm working about two stops short of minimum f-ratio. When I > perform the manual focus, I'm iterating several times until the image I'm > viewing is as in focus as I can achieve in my limited experience, so I'm > wondering if I'm doing anything wrong, or if the camera and atmospheric > conditions are killing my focus. At that range,the focus should be set to infinity. Set it there, and regardelss of what you "see" leave it there. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> value, and I'm working about two stops short of minimum f-ratio. When I >> perform the manual focus, I'm iterating several times until the image I'm [quoted text clipped - 4 lines] >At that range,the focus should be set to infinity. Set it there, and >regardelss of what you "see" leave it there. Or, if the lens is marked incorrectly (being able to turn the ring beyond infinity is sometimes used to compensate for thermal expansion and contraction of the lens and it's housing) try shooting at tiny increments before and after to see how it effects the final result. -Rich |
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