When to use MLU?

jacobsen1 wrote in post #4147881
How does it help on longer focal lengths? Do they just magnify the vibration more?

Yes, longer focal lengths magnify everything. Remember, the rule of thumb for avoiding handholding camera shake is a shutter speed of at least 1/FL sec -- same idea. You can also look at it in terms of angle of view. The vibration would only account for a small fraction of the angle of view of a wide-angle lens but could be a substantial fraction of the much narrower angle of view of a long telephoto lens.

Mirror-slap vibration is an angluar function. The vibration shakes the camera through a given angle. Long focal lengths have small angles of view. Therefore, the vibration angle is a greater percentage of the overall image.

The concept is exactly like camera shake. With an 18mm lens, it is hardly a problem at all. With a 600mm lens, it is a huge problem.

PS:
Hmph! Jack beat me. That's what I get for no knowing how to type.

Waiting 2 seconds isn't going to help if the wind is blowing, trucks driving by or you use a cheap tripod and head. The shutter releasing is going to even add some.

canonloader wrote in post #4148193
Waiting 2 seconds isn't going to help if the wind is blowing, trucks driving by or you use a cheap tripod and head. The shutter releasing is going to even add some.

The funny thing is that, before I bought a wired remote for my Xti, I used MLU all the time simply because I preferred to wait for 2 seconds after pushing the shutter button instead of the 10 second wait for a normal timer shot. I got so used to that procedure that now I sometimes find myself standing around like an idiot waiting for the picture to be taken -- forgetting that I have to push the button on the remote a second time (once for the mirror and again for the shutter).

canonloader wrote in post #4148193
Waiting 2 seconds isn't going to help if the wind is blowing, trucks driving by or you use a cheap tripod and head. The shutter releasing is going to even add some.

True, but MLU minimizes vibration as much as possible.

Player9 wrote in post #4149485
The funny thing is that, before I bought a wired remote for my Xti, I used MLU all the time simply because I preferred to wait for 2 seconds after pushing the shutter button instead of the 10 second wait for a normal timer shot. I got so used to that procedure that now I sometimes find myself standing around like an idiot waiting for the picture to be taken -- forgetting that I have to push the button on the remote a second time (once for the mirror and again for the shutter).

I have many pictures of my shoes or face staring into the camera because I forgot to turn off MLU and press the shutter, wonder why the familiar friendly shutter sound was interrupted, bringing the camera down to look at it and then hearing the k-a-lick, the rest of the shutter firing finally remembering I had MLU set.

canonloader wrote in post #4148193
Waiting 2 seconds isn't going to help if the wind is blowing, trucks driving by or you use a cheap tripod and head. The shutter releasing is going to even add some.

Getting sharp images is a game of "inches." You need to find the sources of vibration and remove them. One of the biggest sources of vibration is from mirror slap in an SLR. The best way to remove this is to use MLU. The mirror goes up, locks, wait for vibration to disappear, fire the shutter.

Go to this link:

http://markins.com/cha​rlie/report4e6.pdf

There are clear measurements and demonstrations of the impact of mirror slap on an image.

You then must ALSO seek to remove the vibration from the sources you cite. To deal with these, one needs a good tripod. The better it is the more more it helps.


J.

John, I saw that before, which is why I said what I did. Vibration can come from anywhere, and usually does. I use to use a telescope with my 30D attached. A long beast. Even on a decent tripod, if I was still touching the thing, I could even "see" the vibration from my heartbeat. So something as small as even the shutter opening and snapping shut will introduce some. The best thing I have seen to dampen vibration so far is beanbags. Solid ones, filled with sand, the kind they use for scoping in big rifles.

canonloader wrote in post #4153698
John, I saw that before, which is why I said what I did. Vibration can come from anywhere, and usually does. I use to use a telescope with my 30D attached. A long beast. Even on a decent tripod, if I was still touching the thing, I could even "see" the vibration from my heartbeat. So something as small as even the shutter opening and snapping shut will introduce some. The best thing I have seen to dampen vibration so far is beanbags. Solid ones, filled with sand, the kind they use for scoping in big rifles.

I don't disagree at all. Mass has a damping quality all its own.

J.

Here's how I see it, from experience. Dampening is better done with something that absorbes the shock easily but slows the shockwave down. Here's a very clear analogy that we can all see. Put the camera and lens on a solid steel block. Nothing more stable than that, right? Then try it on a tightly packed sand filled beanbag. The bean bag will slow and absorb, the steel will bounce it back. Take a hammer and hit the steel block, it bounces back. Take the same hammer and hit that beanbag.

Thats the mental picture I have of it all.

jacobsen1 wrote in post #4146925
Why doesn't it help on longer exposures? Like longer than 2 seconds.

Actually, if there are light trails in the shot, it might help. With a light trail, the mirror slap will show as a small hook in the trail.

If you really want to peep into it, open the image in PS and expand the view to 1600x. That will show any vibration and the angle of it.

I've gotten used to using mirror lockup regularly -- that is, when I'm tripod mounted and taking a picture of a non-moving subject. Wildlife, no, but any landscape or macro that I'm serious about, yes. In addition, with my longer lenses, I keep my IS turned on. Even though most lenses recommend turning IS off when using a tripod, I have noticed enough slight movement using a heavy lens at the long end that I figure IS is better than no IS.

I also noticed that my mid-range Manfrotto tripod was more sensitive to the wind than I was happy with, so, when I bought my 5D I also upgraded to a more solid tripod. In all of this, I'm not trying to be anal about my photography, but I just want to do everything I can to get high quality pics. My skills are still developing, and I want to have things working with me instead of against me.

Tony

MLU is essential when you are using extremely long lens, such as for astrophotography. Once you get about 1500mm even the slightest vibrations can effect your image.

canonloader wrote in post #4153826
Here's how I see it, from experience. Dampening is better done with something that absorbes the shock easily but slows the shockwave down. Here's a very clear analogy that we can all see. Put the camera and lens on a solid steel block. Nothing more stable than that, right? Then try it on a tightly packed sand filled beanbag. The bean bag will slow and absorb, the steel will bounce it back. Take a hammer and hit the steel block, it bounces back. Take the same hammer and hit that beanbag.

Thats the mental picture I have of it all.

The material matters no doubt. It also matters how the camera is coupled to the mass. There are cases where if you add weight, it can actually make it worse (mechanical resonance or underdamped). So, it isn't quite that simple but it is a good description of the benefit of certain properties of materials. That is one of the reasons that CF is used often in tripod legs - it does an excellent job of damping vibration.

Mass has a quality all its own, but it is not as simple as always just adding more.

J.

JohnJ80 wrote in post #4156014
The material matters no doubt. It also matters how the camera is coupled to the mass. There are cases where if you add weight, it can actually make it worse (mechanical resonance or underdamped). So, it isn't quite that simple but it is a good description of the benefit of certain properties of materials. That is one of the reasons that CF is used often in tripod legs - it does an excellent job of damping vibration.

Mass has a quality all its own, but it is not as simple as always just adding more.

J.

Yes, but mass always wins for single impact events. Resonance requires a steady input of energy, a standing wave, to do it's magic. If you were firing the shutter over and over it is possible to hit the resonant frequency and that tiny shutter could move a much larger mass.