Comments on: Tripod Stability Tests, Part I http://regex.info/blog/2007-09-17/575 Not a photo blog, but sometimes I play one on TV Thu, 24 Jul 2008 01:53:21 +0000 http://wordpress.org/?v=2.0.12-alpha by: Jeffrey Friedl http://regex.info/blog/2007-09-17/575#comment-9210 Thu, 20 Sep 2007 14:37:44 +0000 http://regex.info/blog/2007-09-17/575#comment-9210 <span class='jfriedl'>Guys, thanks for your great comments. I've made a <a href='http://regex.info/blog/2007-09-20/578' rel="nofollow">followup post about the shutter speed</a>, which I hope explains my thinking more clearly. —Jeffrey</span> Guys, thanks for your great comments. I’ve made a followup post about the shutter speed, which I hope explains my thinking more clearly. —Jeffrey

]]> by: Alexander Kiel http://regex.info/blog/2007-09-17/575#comment-9200 Thu, 20 Sep 2007 08:22:06 +0000 http://regex.info/blog/2007-09-17/575#comment-9200 Regarding the 1 second exposure: Jeff, If you capture a normal scene with normal contrast (likely not the case with your notebook) than Joe is right. If you set your aperture and ISO to record the whole scene without blowing out hightlight, than the light which is captured during 1% of the exposure time will give you 1% of brightness levels. Just for test: take a sharp image. Duplicate the layer on Photoshop and add a motion blur to it. Than lower the opacity of the blurred layer to 1%. You will see nothing. Thats why the brightest pixel values of the blur (255) have only a value of 2 - 3 now. The same thing happens on your cameras sensor. 1% of the final photon load comes in a bit shaky (oh no its the camera which shakes around the photos :-). But this photos will nearly not contribute to the final exposure. Some time ago I did a test with my tripod and a macro lens capturing the letters of a book. Since I have a D70s, I have no mirrot look-up. I wanted to find out at with shutter speed my camera renders the maximum blur. It was about 1/60s. The firework example is a bit different kind. At shooting fireworks you set your aperture and ISO to match the time one rocket is flying, or to be more precise the time a part of the explosion stays at the same place in your frame. This could be about 1 second. If you capture 10 seconds, you will have 10 rockets in the frame. But the correct exposure for one rocket was 1 second not 10 seconds. Regarding the 1 second exposure:

Jeff, If you capture a normal scene with normal contrast (likely not the case with your notebook) than Joe is right. If you set your aperture and ISO to record the whole scene without blowing out hightlight, than the light which is captured during 1% of the exposure time will give you 1% of brightness levels.

Just for test: take a sharp image. Duplicate the layer on Photoshop and add a motion blur to it. Than lower the opacity of the blurred layer to 1%. You will see nothing. Thats why the brightest pixel values of the blur (255) have only a value of 2 - 3 now.

The same thing happens on your cameras sensor. 1% of the final photon load comes in a bit shaky (oh no its the camera which shakes around the photos :-) . But this photos will nearly not contribute to the final exposure.

Some time ago I did a test with my tripod and a macro lens capturing the letters of a book. Since I have a D70s, I have no mirrot look-up. I wanted to find out at with shutter speed my camera renders the maximum blur. It was about 1/60s.

The firework example is a bit different kind. At shooting fireworks you set your aperture and ISO to match the time one rocket is flying, or to be more precise the time a part of the explosion stays at the same place in your frame. This could be about 1 second. If you capture 10 seconds, you will have 10 rockets in the frame. But the correct exposure for one rocket was 1 second not 10 seconds.

]]> by: Joe Beda http://regex.info/blog/2007-09-17/575#comment-9145 Wed, 19 Sep 2007 04:30:21 +0000 http://regex.info/blog/2007-09-17/575#comment-9145 I think I see what you are saying. I agree that no matter how little shake happens and when it happens, since we are looking at this on a black background, it will be visible. One way to accentuate this is to set the exposure so that you intentionally blow out each color channel. In this case you would probably be sensitive enough to accentuate the blurring. As for the fireworks analogy, think about if you have your sensitivity set way too low for fireworks (say ISO 25 or lower). Or that the fireworks are super special fireworks that move very very fast. In either case, the trails that you'll be seeing will be dimmer because your sensor isn't sensitive enough to register the photos coming in to any appreciable degree. However, I don't think that is what is happening in your test :) Here is another suggested test -- add a gradient ramp to your test image. My guess is that you will blow that out. If you set your exposure so that the gradient is well exposed, the rest of the scene (a dim hallway?) will probably be way underexposed. I think this will show that you are in fact blowing out the image quite a bit which will tend to exaggerate the affect of the shake. Which is probably a good thing for this test. But this is all semantics -- your tests clearly show that to get a good image technique is king followed by good equipment. Good equipment can help make up for bad technique by dampening the vibrations from the bad technique faster. Now I just want to see more examples :) How about a good aluminum tripod, basalt and a good wood tripod. I've heard that wood is best at absorbing vibrations (followed by CF) but I've never used one myself. Joe I think I see what you are saying. I agree that no matter how little shake happens and when it happens, since we are looking at this on a black background, it will be visible. One way to accentuate this is to set the exposure so that you intentionally blow out each color channel. In this case you would probably be sensitive enough to accentuate the blurring.

As for the fireworks analogy, think about if you have your sensitivity set way too low for fireworks (say ISO 25 or lower). Or that the fireworks are super special fireworks that move very very fast. In either case, the trails that you’ll be seeing will be dimmer because your sensor isn’t sensitive enough to register the photos coming in to any appreciable degree. However, I don’t think that is what is happening in your test :)

Here is another suggested test — add a gradient ramp to your test image. My guess is that you will blow that out. If you set your exposure so that the gradient is well exposed, the rest of the scene (a dim hallway?) will probably be way underexposed. I think this will show that you are in fact blowing out the image quite a bit which will tend to exaggerate the affect of the shake. Which is probably a good thing for this test.

But this is all semantics — your tests clearly show that to get a good image technique is king followed by good equipment. Good equipment can help make up for bad technique by dampening the vibrations from the bad technique faster.

Now I just want to see more examples :) How about a good aluminum tripod, basalt and a good wood tripod. I’ve heard that wood is best at absorbing vibrations (followed by CF) but I’ve never used one myself.

Joe

]]> by: Joe Beda http://regex.info/blog/2007-09-17/575#comment-9129 Tue, 18 Sep 2007 17:10:47 +0000 http://regex.info/blog/2007-09-17/575#comment-9129 Re: 1 second exposure. I think I wasn't clear. Push this out the limit and lets talk about a 30 second exposure. Lets also say that it takes 0.3 seconds for any vibrations from opening the shutter, mirror slap, hitting button, etc. to settle. The percentage of the exposure that is subject to vibration is very small in this case -- just 1% of the exposure time. This means that any blurring during that transient vibration will be very dim. However, if the shutter time is 0.3 seconds, then 100% of the exposure will be subject to the vibration. This means that (ignore noise) a 1 second exposure would look better than a 0.3 second exposure. Now -- this is just any transient vibrations due to actually starting the exposure and are probably due more to technique than the actual stability of the support system. Any ambient vibration (earthquakes, stepping around the tripod on soft ground, house moving, trains going by) won't be subject to the same issues, of course. (I wish I had a whiteboard to help describe what I'm saying ;) <div class='jfriedl'><p>I think I understood you (you were clear enough), but I still think that it doesn't matter whether the exposure is lengthened after some vibration-induced blur has been recorded, the blur is still there and isn't diminished by the shutter remaining open. Perhaps you're thinking that I picked an exposure that would be correct based on a 1-second shutter, and in doing so something that lasts only a fraction of that won't create enough light to register well on the sensor, but that's not what's happening here.</p><p> Think more along the lines of a long exposure for fireworks: the length of the exposure doesn't impact how bright any one part of the fireworks show up, but merely how long the trails are, and how many bursts show up in the frame.</p><p> It's the aperture and ISO setting that control how much any one group of photons adds to the final result, so if shake-induced blurring happens only in the first 0.001 second of the exposure, it'll show up whether the exposure is 0.001 seconds, 0.1 seconds, 1 second, 10 seconds, etc. (Remember, my target has a black background, so it's not like subtle blurring will get "washed out" by the background.)</p><p> I don't know that I've explained this well, but there you have it.... —Jeffrey</p></div> Re: 1 second exposure.

I think I wasn’t clear. Push this out the limit and lets talk about a 30 second exposure. Lets also say that it takes 0.3 seconds for any vibrations from opening the shutter, mirror slap, hitting button, etc. to settle. The percentage of the exposure that is subject to vibration is very small in this case — just 1% of the exposure time. This means that any blurring during that transient vibration will be very dim. However, if the shutter time is 0.3 seconds, then 100% of the exposure will be subject to the vibration. This means that (ignore noise) a 1 second exposure would look better than a 0.3 second exposure.

Now — this is just any transient vibrations due to actually starting the exposure and are probably due more to technique than the actual stability of the support system. Any ambient vibration (earthquakes, stepping around the tripod on soft ground, house moving, trains going by) won’t be subject to the same issues, of course.

(I wish I had a whiteboard to help describe what I’m saying ;)

I think I understood you (you were clear enough), but I still think that it doesn’t matter whether the exposure is lengthened after some vibration-induced blur has been recorded, the blur is still there and isn’t diminished by the shutter remaining open. Perhaps you’re thinking that I picked an exposure that would be correct based on a 1-second shutter, and in doing so something that lasts only a fraction of that won’t create enough light to register well on the sensor, but that’s not what’s happening here.

Think more along the lines of a long exposure for fireworks: the length of the exposure doesn’t impact how bright any one part of the fireworks show up, but merely how long the trails are, and how many bursts show up in the frame.

It’s the aperture and ISO setting that control how much any one group of photons adds to the final result, so if shake-induced blurring happens only in the first 0.001 second of the exposure, it’ll show up whether the exposure is 0.001 seconds, 0.1 seconds, 1 second, 10 seconds, etc. (Remember, my target has a black background, so it’s not like subtle blurring will get “washed out” by the background.)

I don’t know that I’ve explained this well, but there you have it…. —Jeffrey

]]> by: RenĂ© http://regex.info/blog/2007-09-17/575#comment-9123 Tue, 18 Sep 2007 09:25:52 +0000 http://regex.info/blog/2007-09-17/575#comment-9123 Nice test, one dreawback: The last handheld shot isn't (much?) motion blurred, it's simply Out of focus ;) <div class='jfriedl'><p>That's certainly a possibility, but unlikely because I used the split-prism of my <a href='http://regex.info/blog/2007-08-22/550' rel="nofollow">Katz-Eye focus screen</a> to make sure that I had the focus nailed each time. Using ISO 3,200 on a D200 really kills the detail due to noise, and 200mm at only 1/250th of a second leaves ample room for blur, especially when pixel peeping like we're doing here.</p> <p>I do notice, though, that all the images tend to lose focus when I look at them after having a beer. I must research this aspect of tripods much more thoroughly. :-) —Jeffrey</p></div> Nice test, one dreawback: The last handheld shot isn’t (much?) motion blurred, it’s simply Out of focus ;)

That’s certainly a possibility, but unlikely because I used the split-prism of my Katz-Eye focus screen to make sure that I had the focus nailed each time. Using ISO 3,200 on a D200 really kills the detail due to noise, and 200mm at only 1/250th of a second leaves ample room for blur, especially when pixel peeping like we’re doing here.

I do notice, though, that all the images tend to lose focus when I look at them after having a beer. I must research this aspect of tripods much more thoroughly. :-) —Jeffrey

]]> by: Joe Beda http://regex.info/blog/2007-09-17/575#comment-9090 Mon, 17 Sep 2007 17:13:47 +0000 http://regex.info/blog/2007-09-17/575#comment-9090 A one second exposure may not be optimal for testing a tripod. If there are some transient vibrations from mirror slap or from hitting the button, they could dissipate during the first part of that exposure. It might be interesting to try a range of exposures to find those that are most sensitive -- not too fast to freeze action but also not too slow to allow the camera to settle. <span class='jfriedl'>During the 1-second exposure, while the camera is settling, the shutter is open, so any movement during the whole time results in a blurred picture. It's sort of a worst-case test, since much better results can be gotten with a more realistically fast exposure. But then again, it's not uncommon to have really long exposures in certain classes of photography (<a href='http://regex.info/blog/2007-04-04/413' rel="nofollow">like these</a>), so the 1-second test exposures are still only a beginning.... —Jeffrey</span> A one second exposure may not be optimal for testing a tripod. If there are some transient vibrations from mirror slap or from hitting the button, they could dissipate during the first part of that exposure. It might be interesting to try a range of exposures to find those that are most sensitive — not too fast to freeze action but also not too slow to allow the camera to settle.

During the 1-second exposure, while the camera is settling, the shutter is open, so any movement during the whole time results in a blurred picture. It’s sort of a worst-case test, since much better results can be gotten with a more realistically fast exposure. But then again, it’s not uncommon to have really long exposures in certain classes of photography (like these), so the 1-second test exposures are still only a beginning…. —Jeffrey

]]> by: Peter http://regex.info/blog/2007-09-17/575#comment-9089 Mon, 17 Sep 2007 16:37:31 +0000 http://regex.info/blog/2007-09-17/575#comment-9089 I like your analytical approach! Looking forward to Part II. Also, perhaps, some equivalent tests of your new monopod would be interesting. I've seen people making subjective claims of gaining 2-3 stops using a monopod, versus hand-held, but it'd be nice to see them substantiated - or not. Peter I like your analytical approach! Looking forward to Part II.

Also, perhaps, some equivalent tests of your new monopod would be interesting. I’ve seen people making subjective claims of gaining 2-3 stops using a monopod, versus hand-held, but it’d be nice to see them substantiated - or not.

Peter

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