How to make multiple exposures in photography

Sometimes you may want to make multiple exposures on the same negative. When I say multiple exposures here, I don't mean the method of synthesizing the image of the moon into other landscape photos through secondary exposure. However, it is not difficult to synthesize such photos. Take a rough landscape map according to your own needs and leave a blank sky (the darker the sky, the better). Now, take a second exposure without taking pictures. This time, expose the moon and place it in the blank sky of the picture. Ok, now you have a landscape map with the moon, but there is actually no moon there. Exposure compensation is not required for both exposures. It should be noted that two exposures did not increase the amount of light reaching the negative, because the image of the moon fell on the unexposed area of the negative.

The problems caused by using this shooting method are obvious. First of all, when these photos are exposed twice, most of the lenses used have different focal lengths. Wide-angle lenses, such as 24mm, are used to shoot scenery, while 300mm lenses are generally used to shoot the moon. We have all seen many similar photos, and we always feel that this mixed perspective effect is problematic. The second problem is that the scenery in the photo and the illumination direction of the moon should be the same, because viewers always think that the photo was taken under the same light source. But most photos of the "moon" are not like this. If you look at these photos carefully, you will find that many of them are a bright full moon hanging in the landscape photos with sidelights. This is absolutely impossible. If it is a full moon, the moon must be under positive light. It can never be a side view of the ground, and the moon is shining, unless you have two suns. There is another problem with this shooting technique. Because shooting the moon is often the second exposure, it will mix some colors of the first exposure. When you expose the moon to the blue sky in dim light for the second time, you will get a moon dyed blue. This is actually not good at all.

The skills mentioned above are not what I want to discuss here. When I say "multiple exposures", I mean multiple complete exposures of the same framing picture on the same negative, which can also be called layered exposure. For example, you may want to take many photos of flowers swaying in the wind, or you may want to take pictures of different flashes in running water. You need to consult the manual of the camera first to see how to prevent the negative from passing through every time you press the shutter. On a relatively new fuselage, you can set the exact exposure times before shooting. On other bodies, you must hold down a button or wrench before pressing the shutter to prevent the camera from crossing the film.

If you use an old-fashioned mechanical camera, let's introduce the process of multiple exposure now. Before shooting the first film, gently move the film wrench along the direction in which the film passes until you feel that the film has passed the end point. Don't be too strong, you just need to make sure that the negative is flat and in place. Now take the first picture, then hold down the film wrench so that it can't rotate in its original position, press the film return release button, and then slowly close the shutter. Repeat the above actions for multiple exposures. (Note: I verified this method is feasible on my Phoenix 205E, although the 205E has the function of multiple exposures. When winding the shutter, be sure to hold down the film release button. )

The question is, if you continue to take a second picture on one picture, how can you be sure that the final exposure result is correct? The best and simplest way is to use gears. Remember that the definition of first gear is half or twice of a certain amount? If you make 2, 4, 6, 8 exposures, etc. , you can use the following method to calculate the exposure. Use the exposure meter to get exposure readings normally. For example, your exposure is 1/30 seconds, f/ 1 1. What is the shutter speed 1/60 seconds to get 1/30 seconds? The answer is two 1/60 seconds. So, if you plan to expose the same scene twice with a negative, and each exposure is1/60s, f/ 1 1, then you will finally get the correct amount of light on the negative. One exposure 1/30s equals two exposures 1/60s, or four exposures1125s, or eight exposures 1/250s, or 16 exposures/kloc-0. The total exposure of these multiple exposures is the same as that of normal exposure.

Although I think this is the simplest method, you can achieve the same result by other methods. First get a reading with the exposure meter, and then reduce the aperture to a suitable position according to the planned exposure times. This method is the simplest method for cameras that provide 1/3 shutter increments. For two exposures, reduce the normal photometric reading by one step. For three exposures, each exposure is less than the normal photometric reading 1 2/3 steps. For 4 exposures, reduce 2 steps; For five exposures, reduce 2 1/3 steps; For 6 exposures, 2 2/3 steps are reduced. 8 exposures, minus 3 files; 16 exposure, minus 4 steps; 32 exposures, minus 5 steps; The same picture was exposed 64 times and reduced by 6 levels.

The third method is to double the ISO value of the negative, which is the same as the number of times you plan to expose it. Set the ISO value of the camera to this new value, and then measure the light, so you can take the same photo as many times as you choose. The advantage of using the method of modifying ISO value is that you can make odd exposures instead of multiple exposures. Suppose you have to make five exposures and use ISO 100 negative. Change the ISO value of the camera to 500, then measure the light and start shooting. One trap is that you must remember to change the ISO value back to the normal setting after shooting, otherwise all the negatives behind will be destroyed. I am used to counting "2, 4, 8" loudly when shooting, instead of changing the camera settings. Even if the camera doesn't make mistakes for me, I often make many mistakes myself.