I often hear photographers preaching the gospel of mirror lockup as a way to achieve sharper images. In fact, when shooting at a popular landscape photography destination like Yellowstone, you'll often hear most of the cameras using mirror lockup.
Mirror lockup is a function available in most cameras (though not some of the entry level Nikons and not in most Sony cameras due to the pelicle mirror). Mirror lockup makes the mirror flip up for a moment before you activate the shutter. The idea is that the vibrations caused by the fast-flipping mirror can cause sharpness problems. Generally, mirror lockup is used by landscape photographers and macro photographers who are shooting from a tripod.
So, in theory, mirror lockup makes sense. It stands to reason that getting rid of vibration would cause sharper pictures–especially for longer exposures. But I've always felt like it was a conspiracy of the camera manufacturers. I think they got together in some high rise in Japan and decided to put one feature in our cameras that was nothing more than a placebo, and they've been laughing about it ever since. “What fools!” they say, as we tout the placebo and use it so we can feel like our photos are sharper than the blockhead next to us who hasn't yet discovered it.
I'm not the only photographer who has doubted the practical effect of mirror lockup (MLU). A previous test was done that is specific to macro photography (and the result was the same as mine). I have periodically used mirror lockup, but to be honest, I've never really seen the difference. I just did what everyone else told me to do.
Mirror lockup has been in cameras for many decades. In fact, some early SLR wide-angle lenses couldn't mount without the mirror locked up. Mirror lockup made more sense in the film days when the mirror flopped with greater force. Since then, efforts were put in the design of the mirror to reduce the vibrations it caused.
The Mirror Lockup Test
This week, I put it to the test. I shot comparison photos for hours on different camera systems, different lenses, different focal lengths, different apertures, different tripods, different distances, and every imaginable shutter speed. I wanted to know once and for all if it was a useful feature, or if the Japanese high rise meeting was real.
I created a spreadsheet and catalogued the camera settings, distance, and many other relevant data points for each of the shots so that no human error could impact the results. After the test was finished, I took the photos to Dustin and had him look at each of the pictures to guage sharpness in a blind test without telling him which shot was and wasn't shot with mirror lockup.
All photos were shot using contrast detection focus with a perfectly well-lit focusing target. Sharpness on the unprocessed photos was judged at 100% view.
The Results of the Mirror Lock-up Test
Mirror Lockup makes absolutely zero visible difference in the sharpness of the photo IF you shoot from a rock solid tripod and ballhead. Period.
When the test was performed on my favorite tripod, there was no difference in the sharpness of the photos at all. However, when we tested lighter and cheaper tripods, poor quality mounts, or if the ballhead was not tightened down properly, mirror lockup made an obvious and profound difference.
First lesson learned from this test: If you use a high quality tripod, mirror lockup makes no difference at all. When I say “no difference” I mean the photos look identical to my eye. This was tested dozens of times at shutter speeds from 30 seconds to 1/2000th and EVERY shutter speed in between.
However, I also tested cheaper camera bases and heads. Second lesson learned from this test: On unsteady or cheap tripods and heads, mirror lockup made a profound difference but the difference was ONLY noticeable between 1/80th down to 3″ shutter speeds. The shutter speed most prone to vibration problems was 1/40th on the cameras I tested. All other shutter speeds showed no difference in sharpness with or without mirror lockup. At fast shutter speeds, mirror lockup makes no real difference because there simply isn't much time for the vibration to impact the photo. At longer shutter speeds such as those used for night photography, the vibration only occurs during a tiny fraction of the overall exposure time, so it isn't noticed.
For advanced photographers who use extremely heavy (and expensive) lenses that have a mount on the bottom of the lens, you should know that in my testing of the 70-200mm f/2.8 lens, I saw that mounting the lens to the ballhead proved to be a very unstable platform. With the lens mounted to the ballhead, MLU made a profound difference at 1/40, but when I mounted the camera to the ballhead with the same settings, there was no difference between the MLU and non-MLU photos. Obviously, the danger in doing this is that the weight of the lens pulls on the lens mount and destroys your camera… so I don't recommend it at all. I only did this for testing.
I'm done with mirror lockup. It is one more setting I can ignore when in a shooting situation. To me, it's important to pare down my gear, settings, and everything else during a shoot so that I can focus on creativity and lighting. It is important to remember that using mirror lockup certainly will not hurt the sharpness of your pictures, but I find that being overly burdened with too many camera settings negatively impacts my ability to make a great photo.
However, if you don't yet have a professional tripod and ballhead (click here to see my good, better, and best tripod and ballhead recommendations), then MLU is one setting you should pay attention to when using shutter speeds between 1/80 and 3 seconds.
As mentioned previously, advanced photographers should know that mirror lockup does make a difference when shooting extremely heavy lenses where the lens is mounted to the ballhead instead of the camera.