Light leaks are a common occurrence in long exposure photography and come from a variety of places. The long exposure times the Firecrest 13 and 16 stop filters allow have shown light leaks coming from the body of the camera while other light leaks come from light passing between stacked filters. A few common ways to prevent this from happening are:
- Place a hat over the top of your viewfinder
- Use gaffers tape to cover the viewfinder and any ports or doors on the camera body
- Gently cover or wrap the lens with a dark scarf, cloth or lens bag with the end cut out (Joel uses this trick)
- Cover the top of the filter holder with a cloth or gaffers tape to prevent light passing between stacked filters
- Use the foam gasket supplied with ProStop and Firecrest filters
It’s best to keep the ND filter closest to the lens. This is to minimize reflections and light leaking behind the ND which will cause significant deterioration of the image. If the filter has a gasket, place the gasket rearward toward the lens to create a light tight seal between the filter and the holder. The rear slot of the Formatt-Hitech holder system may have an additional spacer. This spacer is for using 4mm glass cinema filters. Experiment with using the gasket in and out, especially when using ND filters that include a light gasket.
Two Filters in the Rear Slot
It is possible to stack two filters into the rear slot of the holder system. Simply loosen the screws on the holder system and slip two filters into the slot. If the filters you’re using have gaskets, it’s advisable to place the gasket of both filters rearward toward the lens. This will create a light tight seal between the rear filter and the holder system, and also between the front and rear filters.
85mm and 100mm Firecrest ND and ProStop IRND filters come with a foam gasket. This can be attached to the filter to help prevent light leaks and provides a tighter fit in the aluminum holder. Attaching the gasket is simple. Lay the filter down on a soft cloth, peel the paper off of the gasket, place in desired spot and press down.
If you decide to no longer use the gasket first gently peel off the foam. Any remaining residue can be soaked off in warm water with a mild soap.
Setting White Balance and Focus with NDs
Every camera responds differently to using ND filters. When using a lot of ND, you might get best results from setting focus and white balance with the holder off. Then add the holder right before making the exposure. However, if the live view on your camera is capable of looking through moderate strength NDs, it is preferable to adjust focus and white balance with the filters on the camera in a ready-to-shoot configuration. This lessens the chance of bumping the lens and disturbing your focus or altering your framing.
Adjusting Your Modular Holder System
The filter stages are attached via brass screws. Long screws protruding from the front of the holder system may cause vignetting with wide lenses. One trick is to reverse the threads and let the extra screw protrude rearward. Just be careful when installing and removing your holder system to not scratch the front element of your lens.