How to Lock Focus on Prime Lenses and Anamorphic Lenses
To focus a single focus anamorphic lens, you need to focus the prime lens and anamorphic lens to infinity, and then use your single focus attachment to rack focus. If you have the appropriate anamorphic lens kit, you can even set your focus infinity to a closer distance, and use your rangefinder to macro focus anamorphic. This is a pretty simple process and outlined in our articles.
This article does not apply for dual focus anamorphic lenses. Follow this method to focus dual focus anamorphic lenses.
However, filmmaking can be a rough business. If for whatever reason, your camera is knocked about, or an inattentive operator moves the lens, your focus on either your prime lens or anamorphic lens does not stay on infinity, your image will become unfocused. Even a small movement on your prime lens, for example, may not be apparent until you ingest your footage for editing, desqueeze it, and view it on a large monitor. This can be obviously frustrating.
LOCK FOCUS ON YOUR ANAMORPHIC
Some of our anamorphic kits come with the ability to lock focus on your anamorphic lens. This solves half of the problem by ensuring your anamorphic setup stays locked at infinity and your single focus does all of the work.
Our Isco Micro comes with a built in single focus lock. Our Schneider XL single focus anamorphic lens kit is locked at infinity at service, so it will have no issues with focus lock. The other kits do not have focus lock mechanisms. Even if your anamorphic lens is locked, you’ll still need to lock your prime lens. Again, dual focus anamorphic lens do not apply here, because you will need to focus both prime and anamorphic to achieve focus.
If your Isco Micro was an older version that did not come with a locking mechanism, contact us as we may have spares available for sale.
LOCK FOCUS WITH YOUR PRIME LENS
The need to lock prime lenses has traditionally been unusual. Generally, the only need for fixed prime lens focus would include projection lenses and cinema applications. Most lenses that you would work with for handheld and movie cameras did not need and thus do not have the ability to lock at infinity. But when using anamorphic lens kits, this would be very helpful.
So we came up with a simple and cheap way to lock your prime lens at infinity, and keep your anamorphic images tack sharp, available with parts available at any hardware stores, for less than $20!
WHAT DO YOU NEED?
You should be able to find these parts at most hardware stores. If not, Amazon or eBay should have what you need. Begin by measuring the diameter of the prime lens you want to use. You don’t have to be accurate, only within a range.
- Pipe clamp (also sometimes known as a duct clamp, or hose clamp)
- Marine weather stripping
- Scissors and screwdriver
Pipe clamps come in diameter ranges. Select one that has a minimum diameter at least 10 percent greater than the diameter of your prime lens. You can use the same clamp on multiple lenses, but switching them may be difficult. The parts should be inexpensive enough, so if you want to lock multiple lenses, then purchase multiple pipe clamps. Marine weather stripping usually comes in lengths of 10 feet or so, so you will only need to buy one strip.
BUILD THE LOCKING MECHANISM
Multiply your diameter by pi (3.16) and cut your marine weather stripping to that approximate length.
Unscrew your pipe clamp so that it can very easily fit on your lens, with weather stripping attached.
Peel off the adhesive on the marine weatherstripping, and attach it to the inside of your pipe clamp.
Place the pipe clamp with weather stripping above the focus ring of your prime lens. With your screwdriver, tighten the pipe clamp until the focus ring can move, but only slightly.
Now, set your infinity focus on your prime lens. Once set, tighten the pipe clamp down. This should apply enough pressure across the marine weather stripping to stop the focus ring from shifting at all. Your setup should now be perfectly locked!
If you have found this anamorphic editing guide interesting and are further interested adding anamorphic lenses o your toolbox as a cinematographer, please visit our anamorphic lens store for demos and examples. We have spent several years collecting, modifying, and testing anamorphic lenses to weed through the junk, make needed modifications, and assemble ready-to-shoot packages.
If you are interested in learning more on working with anamorphic lenses and DSLR, please check out our anamorphic tutorial blog for more anamorphic tips and tutorials!