Understanding Manual and Autofocus Lenses

When it comes to photography, achieving tack sharp focus is crucial. This article explores the nuances of focusing with manual focus lenses on DSLR cameras, particularly on the Pentax brand, which has backward compatibility with older manual focusing lenses. It also delves into the recent advancements in adapting manual focus lenses for autofocus using adapters.

Backward Compatibility with Pentax DSLR Cameras

The Pentax brand is renowned for its compatibility with older manual focus lenses. Any Pentax DSLR will work harmoniously with manual Pentax-K mount lenses or even vintage M42 screw-mount lenses. The phase-detect AF-engine in Pentax cameras can assist in achieving focus without traditional manual focusing aids, making it easier for photographers to get the desired sharpness.

Capabilities of the Pentax Phase-Detect AF-Engine

On a Pentax DSLR, you can set the camera to Manual Focus (MF) mode. You can choose any focusing point as you would in AF-mode. By activating the AF function and moving the focusing ring on the lens, the camera will beep to confirm focus. Simultaneously, a visual confirmation is shown in the viewfinder, providing a straightforward and intuitive focusing experience.

Adapting Manual Focus Lenses for Autofocus: The Role of Adapters

For many photographers, adapting manual focus lenses for autofocus has been a subject of interest. While it's true that a camera needs autofocus lenses to achieve autofocus, recent technologies have made it possible to autofocus with manual lenses using specialized adapters.

Several years ago, the TechArt Pro LM-EA7 adapter was introduced to enable the autofocus of manual lenses on Sony E/FE lenses. Since then, similar technology has been developed for Sony E/FE and Nikon Z bodies. This adapter, among others, works by moving the entire lens closer to or farther from the sensor in response to focus commands from the camera body. The camera’s normal autofocus mechanisms are then applied, allowing for fairly competitive autofocus performance.

However, the adapter has limitations. It is generally thin, accepting Leica M mount lenses or any other lens with an adapter to M mount. While this thinness allows nearly any lens to be autofocused, it also limits the range of movement to just 4mm on the LM-EA7. This is adequate for many wide-angle lenses but insufficient for longer focal lengths or macro lenses. For these lenses, approximate manual focusing followed by tweaking via the adapter is necessary for precise focus.

Operational Mode of Autofocus Adapter

The operational mode of the adapter is quite interesting. For "unit focusing" lenses, the adapter works perfectly. However, for lenses that focus by moving internal groups (internal focus or close-focus correcting lenses), there might be a slight impact on image quality. Practically, the quality difference is often not significant even when not in unit focus mode.

Another benefit of the adapter is that it can allow for closer focus than the lens can achieve on its own. By manually focusing the lens to its close limit and then using the adapter, it's possible to create a variable-length extension tube up to 4mm in length. This can enable a wide-angle lens to focus significantly closer than it normally would.

Conclusion

In summary, while manual focus lenses traditionally required manual adjustment, recent adaptations have opened new possibilities. Pentax cameras provide an excellent platform for using older manual lenses with modern focusing aids. Additionally, adapters like the TechArt Pro LM-EA7 can transform manual focus lenses into capable autofocus tools, albeit with specific limitations. Understanding these techniques can significantly enhance a photographer's ability to achieve precise and sharp focus in various photographic situations.