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Old May 31, 2009, 11:45 AM   #1
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Default Image Stabilization and Light Weight Tripods

I somewhat posed this question in the Pentax forum and thought I would go for a wider audience. I had the opportunity in San Diego a couple of weeks ago to take some night images of the harbor on Coronado Island. I liked the images very much, however I have a lingering problem or a question. I was using a Pentax K20 with a 16-45/f4 lens, a light weight plastic travel tripod, wired remote shutter, mirror up with a delay, and I turned the in body image stabilization OFF. I took an entire set of images this way.

So the question is, the sharpness of time overall image for night I think is pretty good, but should it be better? The names of the boats are a bit fuzzy, not sharp. However, the point sources of the lights in the background (which are on land), do not show any jitter. Is the light weight tripod inducing some vibration? - Would leaving the image stabilization on help with this problem (or is it a problem at all)?

In looking for a new travel tripod (this one broke after 4 years of use), I came across this item of interest. If you scroll down towards the bottom, there is an interesting discussion about stabilization being on or off with some results....

http://photo.net/equipment/velbon/343e/

So, I'll include the overall image, along with 2 - 100% crops.

K20D, DA 16-45/f4, 8.2 seconds, ISO 100, 20mm, f4



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Old May 31, 2009, 11:46 AM   #2
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Here is a 100% crop of the stern of one of the boats....
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Old May 31, 2009, 11:49 AM   #3
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... and then as a point of reference, a set of lights off to the right hand side just above the boats that are on land.

So, with a light weight tripod, should stabilization be on or off? Or was this just a difficult situation in which to obtain a really sharp image?

Thanks!!!!
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Old May 31, 2009, 1:27 PM   #4
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Nikon recommend that VR (image stab.) is switched OFF when using a tripod. The only tripod I have which is any good, is my Bogen #3246; occasionally I'll use a monopod (with a foot strap), but (IMNSHO) "effective, lightweight tripod" is an oxymoron.

Another trick is to use a bean-bag (easy to make your own, but they're available for $$).

Hand-held shots taken with a heavy camera have less problems with shake than those taken with a light camera (think about it…), but back to your original question, time-exposures require the camera to be stable; i.e. if you're using a tripod, it needs to be stable, and not flop around in the breeze, or be shaken by vibrations in the floor/ground. You might try hanging a cinder block or two beneath your lightweight tripod (to make it more effective… …don't laugh, I've done it myself, to great effect!)†

er, that's it…

- Wil

† it's easier to carry a good, heavy tripod around than a lightweight tripod plus two cinder-blocks

PS: …more thoughts: boats in a harbour are continuously moving ever so slightly; even when it looks calm there is always a slight swell on the water, so time-exposures can be very difficult, no matter how well-anchored your camera.

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Old May 31, 2009, 6:47 PM   #5
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Based on the picture, I would say you don't have a problem with the tripod. It doesn't appear that motion blur is causing the softness in the picture.
There are two possible, more likely explanations. The first is that the lens, as many are, is a bit soft at its widest aperture, and the only real way to check is to take a series of shots of the same scene at various apertures and compare.
Secondly: there have been quite a few reports of front or back focus issues with this lens/ camera combination, and that could be contributing to the lack of sharpness at the 100% views. A combination of these two things could also be a factor.
That said, I don't think that you are going to have any problem with prints up to about 11x14" from a shot like this.

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Old May 31, 2009, 7:37 PM   #6
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Hi Brian,

I have to thank you, I believe that your analysis is spot on, in that it is a focusing problem. I went back and took a look at the entire set of images from that evening, and the problem is the idiot behind the camera (me). If I remember correctly, due to the contrast and the light levels, I was having problems focusing, so I switched to manual. I was using Bibble Pro and for the meta data it does not show focus type, however the Pentax browser does, and it was manual. The night before, it appears that I had some similar problems. I happened to find a shift from automatic to manual, coupled with a change in focal length, and the sharpness degraded. I have used the lens quite a bit on my K100 (6mp), and now the K20 (14mp) is much less forgiving.

I went back and check one additional item. Stabilization was off on each of the images, so as to the basic question of having stabilization active while on a tripod, I guess its still open. In the past, I never disabled it and saw no ill effects (k100 though). On additional interesting note - the new Pentax K7 body has removed the external stabilization switch and moved it to a menu item, so the thought may be that its less important to disable it. Just something else to sort out.

Here is a 100% crop, same lens wide open (f4), essentially the same focal length, from the previous night, different location, and its a lot sharper - right down to the pixel level... So the problem, mystery is ... idiot behind the camera (me)! I do have to say that with the 500+/- images I have shot with the K20, the two primary lenses, 12-24 and the 16-45 have been very good - no front/back focusing adjustments, given I get the focus adjusted correctly in manual. In difficult lighting situations, auto focusing is a problem - hence the switch to manual, and now I need to remember to recheck the manual focusing, if I touch the body/lens while on the tripod.

Thanks again!!!
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Last edited by interested_observer; May 31, 2009 at 7:56 PM.
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