camera iris

DSLR lenses and flicker

Canon and Nikon DSLRs give the best image quality with Stop Motion Pro, however there are some issue with lens selection that are important to consider.

Inside all lenses is an iris mechanism, which sets the amount of light that reaches the sensor. An iris looks like this:

The lenses that are supplied with modern DSLRs use automatic iris. This means the lens is normally 'wide open' to let the maximum amount of light through to the viewfinder making it easier for you to see your composition. When you click the shutter release, the lens iris 'stops down', the shutter opens, after the set exposure time, the shutter closes and the lens iris opens up again.

Unfortunately the lens does not 'stop down' to exactly the same place each time you press the shutter. For normal picture taking this is not a problem, but for animation it causes an annoying flicker.

manual lensTo solve this problem, the best solution is to use older style manual iris lenses, not to use the lenses that usually come bundled with the new DSLR cameras. The lens on this page is a manual iris/aperture lens. You can tell by the aperture "f-stop" markings on the movable ring on the lens barrel. Look for this stepping ring with similarly marked increments when considering a lens.


If you are using a Canon DSLR

Adapter rings are available to mount alternative brand lenses on the camera. For example Nikon or Olympus manual lenses onto a Canon.

On Ebay use the following search terms:
eos adapter

For lenses, use the following search terms on Ebay:
Olympus OM1
Olympus OM2
Nikon AI

The appropriate focal length is determined by your production requirements, 28mm or 35mm are versatile choices.


If you are using a Nikon DSLR

There are 2 main sources of manual iris lenses, either Ebay or new from Nikon.

Use the following search term on Ebay:
Nikon AI

The appropriate focal length is determined by your production requirements, but 28mm or 35mm are versatile choices.

For close work you can also consider simple screw on macro lens filters.

The adapter rings and lenses may also be available from you local camera shop.


Basic lens theory

The lower the f-stop number, the more light is let into the camera. This means to get the right exposure a faster shutter speed will be required. Use the DOP control tool in Stop Motion Pro to evaluate this.

The lower the f-stop number is, the less distance is in focus, this is refered to as "depth-of-field ". A shallow depth of field is created when a low f-stop number is used. If you want more depth in focus, use a higher number f-stop, and a slower shutter speed.



Flickering of the animation in playback can be caused by a range of issues. Besides the aperture issue mentioned above, other sources of flicker include:

- Animators /people on set wearing reflective clothes and standing in different places during capture. Solution is to wear dark clothes, capture from the same position each time. Also consider ways to minimise light spilling on areas not in shot.

- Voltage variations - if you are working near an industrial area or the power supply is variable (or if a fridge turns on and off or a washing machine activates on the same power circut) you will get flickering lights. This is very hard to control. UPS (uninteruptable power supplies) can smooth out fluctuations to an extent, however it is difficult to eliminate flicker without having a totally dedicated power supply.

- Turn screen off during capture to reduce ambient light (in Stop Motion Pro, choose View > blank screen during capture). Some studios mask the monitors with cardboard when taking an exposure.

- Use a higher f-stop. Some cameras seem to have less flicker with higher f-stop values.

- Remove flicker in post production with a software anti-flicker tool there is a discussion forum on Vimeo regarding this issue, which is common for timelapse photograpy.


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