Snap-in Bahtinov focus mask for DSLR camera lenses with 77mm filter thread. Manufacturer part number FP443. Requires user to provide a UV or other filter for their camera lens (not included).
Please Note: The Bahtinov focus technique, when used with camera lenses, works best with longer focal lengths. It gets less useful and harder to focus with shorter focal lengths. The practical useful limit for this is around 100mm lens focal length or longer.
About the Bahtinov Mask:
Farpoint Bahtinov Masks are by far, the easiest, fastest and most consistent manual focusing aid available to the amateur astrophotographer. In 2008, Pavel Bahtinov, a Russian amateur telescope maker and astronomer, published an ingenious new way to easily focus your DSLR camera, webcam or CCD camera for astrophotography. The method is simple, very intuitive, and the device has universally been named after the inventor: The Bahtinov Mask.
Prior to the innovative design of the Bahtinov Mask, astrophotographers could spend ten minutes or more just obtaining a reasonable focus. Problems with seeing, exposure length, and camera noise all increased the difficulty of and time spent finding perfect focus. With the Farpoint Bahtinov Mask, the process of finding the perfect focus whether it be through a DSLR, CCD or a WebCam takes a matter of seconds because the process is unaffected by seeing, noise and allows short exposure lengths!
Using the Bahtinov Focus Mask for DSLR Camera Lenses:
Focusing with your Bahtinov mask for DSLR camera lenses is simple. Start by snapping the Bahtinov mask into an inexpensive UV or Skylight filter that fits your camera lens [FILTER NOT INCLUDED; MUST BE PROVIDED BY BUYER]. Center a fairly bright start in your camera and achieve a rough focus, then loosely screw the filter holding the mask onto your camera lens.
Take a short exposure. The image of the star will show diffraction spikes. The "center" set will most likely be shifted to one side or the other. This is showing the defocus.
Adjust the focus of your camera and re-expose the star, once again showing the diffraction spike pattern. Iterate the process until you get the central diffraction spike centered against the star and the other spikes. When you achieve a symmetrical pattern, you have achieved the best possible focus. Remove the mask, center your target object and take your images!
These masks are designed to snap onto a UV filter. The Farpoint snap-in Bahtinov Masks do NOT include a filter. Typically, photographers keep a UV filter on their lens permanently just to protect the lens. Since camera lens filters are stackable, Farpoint recommends that you keep a UV filter permanently on your lens and then LOOSELY thread a second UV filter with the snap-in Bahtinov onto your protective UV filter. That way, your lens will always be protected and you will be able to easily remove the Bahtinov to take your photos. In addition to DSLR camera lens Bahtinov masks, Farpoint also makes Bahtinov masks for telescopes (sold separately).
Farpoint manufactures this "lifesaving" astrophotography tool out of virtually indestructible ABS plastic in a range of sizes for DSLR camera lenses. The Farpoint Bahtinov Mask will ensure that you spend more time imaging and less time focusing for years to come! Whether you focus manually or electronically, the Farpoint Bahtinov Mask is an essential tool for any astrophotographer.
Product Video: How to use a Farpoint Bahtinov focus mask with DSLR camera lenses
Product Video: How to use a Bahtinov focus mask for your telescope