(Note: this post will be of interest only to camera geeks)
My previous post contained a superficial listing of considerations for building a tripod, and left off wondering how to test the effect of various ways to use a tripod. For example, how detrimental is it to add a center column? How beneficial is mirror lock up? Since getting my really nice tripod, I find myself wanting to learn how to use it properly, and these questions are a big part of that.
I tend to dive into things looking for answers, as evidenced by the posts in my photography-tech category, such as my auto-focus test chart, my analysis of NEF compression, my seven-page writeup on digital-image color spaces, or my Lightroom metadata-panel presets builder. In this case, I'm not really sure how to proceed, but I've come up with some tests and results that at least form a basis for further study.
I'm not really sure how relevant the test I'm about to present are, both in theory and in how I executed them. One of the reasons for my writing this post is to solicit comments on the validity of my methodology and interpretation.
I created a simple test-pattern image, shown here at quarter size (click to see the full-sized version):
I set up my tripod at one end of the longest hallway in my home, and displayed the test pattern on my laptop's screen at the other end 16m (53 feet) away. I mounted the big Nikkor 70-200 f/2.8 onto my D200. My goal was to get something that had bulk to challenge the tripod support system, and also reach (high magnification) to exaggerate the effects of any instability. (Frankly, a 200mm lens is not really very much magnification, but it's the best that I have at hand.)
To give you an idea of what I am testing with, here's a picture from my tripod post showing the camera and lens mounted on my ballhead.
Kodak DX6490 — 1/500 sec, f/4.5, ISO 80 — full exif
I took dozens and dozens of one-second test exposures under various conditions. (See this post for a discussion of why a one-second shutter speed was chosen, and for other technical details about how the tests were performed.)
For reference, here's what one of them looked like, with my laptop showing the test screen in the center:
Cropping out all but the center part of interest, the result might look like this:
Nikon D200 + Nikkor 70-200mm f/2.8 @ 200mm — 1 sec, f/8, ISO 100 — full exif
I took long one-second exposures to highlight the ill effects of vibration and instability. The example crop above might not look very sharp, but considering that it's a one-second exposure and that it's a 1/44th-crop from the full frame, I think it's pretty good.
It seems especially good when you compare it to using a bad tripod, or handheld without a tripod. Mouse over the buttons below this next image, to compare among a few different results...
mouseover a button to see that image
I'll talk about these and other results in more detail in another post, but these are some of the most broad results for which the conclusions were already fairly predictable: a good tripod is better than a bad one, and a bad one is better than no tripod.
For reference, here is a bit about the images being compared...
All but the last are one-second exposures at f/8 and ISO 100. It's crazy to try to hand-hold a 200mm shot for one second. (Heck, I was lucky to get a 17mm shot crisp at 1/8th of a second in this post).
So, the final “handheld (sane?)” shot uses all the technology my camera has to offer to better my odds at a less-shaky result. I opened the aperture three stops (from f/8 to f/2.8) and bumped up the ISO five stops (from 100 to 3,200), which allowed me to increase the shutter speed by eight stops (from 1 second to 1/250th of a second). Even then, the shake is still much worse than the “good tripod” result, not to mention the lower quality due to the high ISO and less-sharp aperture.
The “good tripod” represents bad technique with a reasonably good tripod: I used my Gitzo tripod with its center column down and only three of the four leg sections extended. That's all fine, but the bad technique is that I pressed the shutter button by hand rather than using a remote shutter release.
The “bad tripod” version used the same bad technique, but with a flimsy tripod totally inappropriate for the big camera and lens (a Velbon ULTRA MAXi F, described here).
Finally, the “Most Solid” version used my big Gitzo legs without any leg extension, no center column, and no ballhead (using the Really Right Stuff B2-Pro quick-release clamp from my monopod bolted directly to the legs). This is a fairly impractical setup, but extremely solid and stable, so I use it as a reference. I also used mirror-up mode, waiting at least 10 seconds after putting the mirror up before activating the shutter.
In a future post, I'll use some of the other 66 test images to isolates the effects of using mirror lockup, a remote shutter release, all four leg sections (compared to three leg sections), a center column, and more.