Still camera manual lenses were designed to be used with still film. The size of the film area exposed was bigger than the size of the sensor chips used in digital still cameras. As a result, the focal length will be slightly different from what is indicated on the manual lens. In other words, the field of view or how much of the scene you see will be different. If you put a film camera next to your digital camera and put the same manual lens on both, you would find that you could see more of the scene in the film camera’s viewfinder than the digital camera’s viewfinder because the chip is smaller than the film. For a DSLR, this is expressed as a crop factor of 1.6×. To get the effective focal length of a manual still lens on a DSLR, you would multiply the focal length by 1.6. So a 28-mm manual lens placed on a Canon DSLR would have the field of view of a 44.8-mm lens on a film camera. In other words, you will see less area. The important thing is to get rid of the possibility of flicker on your masterpiece by using a manual lens.
Speaking of Flicker
Here are some great tips from the Stop Motion Pro web site.
Minimizing Flicker
Does your animation “flicker” when you play it back? Here are some tips to minimize flicker and achieve a more professional result.
Flicker is an issue that affects everyone who animates. Basically the light intensity changes between frame captures and this change is reflected by a flickery movie when played back. It can be a frustrat- ing issue to resolve, with professional studios spending many thousands of dollars to avoid it. These tips start at the most common causes, which happen to be the easiest to fix, so we suggest starting at the top and ensure you have minimized each step before moving onto the next. It is easy to become obsessed with flicker in your animation. Try not to let the pursuit of flicker-free animation stop you from the real task of making animated films!
Minimize Flicker, Step 1: Camera Basics
The camera is a key tool in animation; if functions are left in an auto mode, then changes to your characters or subject matter on set will result in minor adjustments going on inside the camera in between frames, causing flicker. Minimize this by doing the following:
Lock exposure. Go to a manual mode, which locks the aperture of the camera.
Lock shutter speed. Some web cams refer to this as “gain”; some video cameras have auto shutters,
which can change the exposure time; ensure these are turned off.
Lock white balance. This is very important. Avoid leaving your camera set to auto white balance, as
changes on set mean the camera will change the color balance in between frames. Set the white balance to whatever lighting you are using: tungsten (indoor), fluorescent, outdoor, and so on.
Minimize Flicker, Step 2: Lighting Basics
Control your light sources as much as possible. This means try to avoid having outside light creeping in on your set; when the sun goes behind a cloud outside, or if you stop for a cup of coffee, the light will change, resulting in flicker. If possible, black out all windows and doors; it is important, however, to keep fresh air coming into your workspace, so you will need to consider this. If you really want to control light, paint the room black, and avoid any surfaces that reflect light in the room. You better check with whomever owns the building before painting rooms black.
Minimize Flicker, Step 3: You
What you wear while animating can result in flicker! Try to wear black or dark clothing. In professional studios, people often duck under tables or under the set to avoid reflections and light bouncing off them in between frames. It makes a big difference. Try animating a scene with a white shirt on and then with a black shirt; you will notice less flicker when wearing black. Your body may also block or unblock a light source or reflection in between frames, causing flicker.
Minimize Flicker, Step 4: Your Computer Monitor
Yes, your computer monitor is a source of light, and it may cause visible reflections on set or off you and onto the set.
Minimize Flicker, Step 5: Your Power Supply Is Problematic
Changes in light may be due to different loads on the power coming to your home/studio. This is difficult to eliminate and is discussed later. If you are using a video camera or web cam, turn Stop Motion Pro’s frame-averaging function to 10 to 20 frames. This will help to smooth out the variations somewhat. Note too when a refrigerator, washing machine, or other electrical appliance is operating; it can cause fluctuations in the power going to your lights, and therefore the intensity.
Advanced Flicker Reduction Techniques
If you have worked your way through the preceding suggestions and are still experiencing flicker that you find unacceptable, you need to move to the next level of flicker reduction. These techniques can be time consuming, cost money, and may not work in your situation, so please take this as general advice that are suggestions only. We do not want to encourage anyone to undertake tasks that are beyond their competence.
You should run tests using the Time Lapse tool in Stop Motion Pro at different times of the day with no one on set and with your studio lights running. See if flicker is evident, with a range of shutter speeds if possible. In our small studio, the power supply becomes more unstable (resulting in flickery lights) in the early to midevening, when everyone in the suburb comes home and turns on their appli- ances perhaps! Stormy/windy weather can play havoc with mains power.
Minimize Flicker, Step 6: Your Shutter Speed
If you are using a digital still camera, be aware that fast shutter speeds may contribute to flicker (faster than 1/10 of a second). Mains-powered tungsten lights and fluorescent lights with magnetic (rather than electronic) ballasts cycle in unison with the mains power supply; this means the lights are going on and off between 50 and 60 times a second. If your shutter speed is too fast, you will capture during the lighter or darker part of the cycle. Some studios solve this problem by changing to DC rather than AC power. You can minimize the effect by using a longer shutter speed.
Fluorescent replacement globes (that go in tungsten light mounts) often have “electronic ballasts.” This means the lights flicker on and off thousands of times per second, thereby minimizing the flicker effect. Professional fluorescent light fittings have electronic ballasts. You should always check.
Minimize Flicker, Step 7: Your Lens
If you are using a DSLR camera with a removable lens, you may have an issue with the aperture open and closing (and being slightly different) in between frame captures. Every time a DSLR takes a shot, the aperture of the lens is shut down to whatever the aperture is set to; once the shot is taken, the aperture opens up fully again, giving a nice, bright image in the viewfinder. Slight variations in how closed the aperture is may result in flicker. This is a tricky problem to solve. You may want to turn this feature off if possible, or try using lenses that are 100% manually operated. We have heard of
one studio that simply unscrews the lens slightly and therefore disengages the auto mechanism; we are not suggesting you do this. Another professional studio actually pulls the lenses apart and removes this mechanism entirely.
The most popular option is to use a manual aperture lens on the camera. This keeps the aperture locked throughout the shot, giving even exposures. Canon lenses will need an adapter; these are inexpensive and available from eBay and other online sources. Look for a Canon EOS mount to Nikon lens, for example. Other popular lenses are older Olympus, M42, Carl Zeiss, and Pentax brands.
Minimize Flicker, Step 8: Your Power Supply, Part 2
If your power supply seems to vary a lot (after running the time lapse test outlined earlier), you may need to consider other alternatives. One option may be to go to a constant (“always online”) uninter- rupted power supply (UPS) for your lights. These are quite expensive, especially if you have a large lighting load, and may or may not work. However, they are worth testing. We have had success with a line-interactive UPS, much cheaper than an always online UPS, by turning it off (causing it to switch to battery backup power) when capturing frames. We found that the supply needed a couple of seconds to stabilize when turned off. Again, this may not fix your issue. We use electronic-ballast fluo- rescent lights, which have a much lower power load than tungsten lights (and are much cooler). After all this, you may be required to call in a professional electrical engineer to outline ways to sta- bilize (“clean”) your power, just like the big studios do.