9/15/2023 0 Comments Helios lens photosIn the case of many photographic lenses, their focusing rings stop at infinity. However, looking back at the diagram, we can see that an object at infinity presents the case with the shortest distance from the lens to the film. We've seen that we can just bring the lens closer to the film plane with the focusing ring, and achieve proper focus on the subject we want to photograph. So we can actually use the focusing ring to move the lens ~2 mm closer to the film plane than we normally would for a M42 camera. The lens, like most, uses a helicoid mechanism to translate the twisting of the focusing ring into a movement of the lens further from or closer to the film plane. on the right) where the image of the desired object forms. In order to take a clear photograph of one of the sources, we must insert our film at the point behind the lens (i.e. Of course, the remaining source in the centre forms an image between the other two images on the right of the lens. The source closest to the lens forms an image the furthest away from the lens. This forms an image on the right of the lens that is the closest to the lens of any of the images. Way off the left of the diagram millions of miles away such that the rays coming from it are perfectly parallel. The first source is something at an infinite distance from the lens. Even though the image is being formed in front of the film plane, we can just twist the focus ring, right? Let's take a look at this diagram showing three sources on the left side of the lens forming three images on the right side: Ignoring the fact that a 20th century Soviet lens is being mounted to a 21st century digital body, all we've done is equivalent to inserting a ~2 mm extension tube between a M42 lens and a M42 body. Even though I always knew I'd be modifying it before buying the lens, the lens is still usable for some tasks without modification. If you think about it, all is not lost yet. Many other camera systems have a FFD short enough that, even with the thickness of an adapter, they can still use M42 lenses without issue.īut wait. This is increasingly the case as mirrorless cameras become more common, as these generally have much shorter FFDs than SLRs by their nature of omitting a mirror and pentaprism. Nikon F-mount has one of the longer FFDs of modern consumer cameras. Note that on some other camera systems, this is a non-issue. This means that, once assembled with the camera, the lens will be forming an image just over 2 mm ahead of the film or sensor. A quick measurement when mine arrived in the post showed a 0.95 to 1 mm thickness. Compounding this problem is that the lens mount adapters out there for these two mounts all add some thickness into the mix. This means that when we put the lens onto a Nikon camera, the film plane will appear too far away, and the image will form just ahead of it. These numbers spell trouble: the FFD of the Nikon F-mount system is longer than the system the lens is designed for. This is where some added complication for Nikon conversion comes in. It is the distance between the flange of the lens mount and the film plane. The flange focal distance is particular to each lens mounting system. However, there is a "gotcha" in that the flange focal distance is different between the mounts. There are adapters available cheaply from the usual suspects which M42 lenses will thread into, converting them straight to Nikon F, mechanically. Fortunately for me, this is about as easily said as done. Not having any cameras that take M42 lenses, I set out to adapt and (reversibly) modify this lens to work with a mount I can work with-the Nikon F mount. These lenses were made in the USSR, and the example I got was made for the M42 screw mount. Near the end of 2019, I purchased one of the notorious Helios 44–2 58 mm f/2 lenses. Written: Helios 44–2 lens for Nikon F mount Simple 1983 USSR 58mm f/2 lens modding
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