One of the main benefits of using a M 4/3 sensor is that crop factor makes it easy to shoot objects that are far away. The sensor on the Panasonic GH5 has a 2x crop when compared to that of full frame. For documentary or news shooters the extra focal reach that can be achieved from using a camera like the GH5 can come in very handy.
Need more reach? Try Extra Tele Conversion
To get even greater focal length range there is a feature on the GH5 called Extra Tele Conversion. In this mode you can you can capture video or stills images up to a certain magnification with what Panasonic claim is no deterioration of the picture quality. When recording in 4K/UHD this mode gives you a 1.4x crop to your image while still recording in 4K/UHD. If you are shooting in HD you can get a whopping 2.7x crop.
To test the Extra Tele Conversion I put a 300mm Nikon f/2.8 prime lens on the GH5 and recorded externally to the Atomos Shogun Inferno in UHD 422 10bit, and internally in 422 10bit 25p. I also recorded in HD 420 8bit internally and 422 10bit externally. I wanted to see if Panasonic’s claim that there is no deterioration to the image quality was true.
From my tests I cannot discern any noticeable difference in image quality when recording in UHD 422 10bit and using the Extra Tele Conversion function. I did find that the image when using the Extra Tele Conversion was cleaner than taking the original footage and blowing it up 140%.
Extend your focal length with no loss in quality
This is good news for users of the GH5 as being able to use this function really allows you to extend the focal length of any lens without quality loss to the image. If you were using a Speedbooster this function is going to offer you the best of both worlds. You will be able to take advantage of using full frame glass to get a wider field of view, and then engage the Extra Tele Conversion to shoot at longer focal lengths.
HD v UHD
When you use the Extra Tele Conversion function shooting in HD the crop is 2.7x as opposed to 1.4x when recording in UHD. This is a fairly large increase and I wanted to see just how usable it was. From my tests I found that you can still get pretty good results. The 2.7x increase definitely shows up more noise and it is not nearly as clean as recording in UHD, but I wouldn’t hesitate to use it at lower ISO settings. Again just like with the UHD tests, I did find that the image when using the Extra Tele Conversion was cleaner than taking the original footage and blowing it up 270%.
GH5 Digital Zoom: a pleasant surprise
If you want to even further extend the reach of your lenses Panasonic also offers a 2x and 4x digital zoom function. Normally these tend to be horrible and produce unusable images. I tested this digital zoom modes out by combing them with the Extra Tele Conversion function to see what sort of results were obtainable. The 2x Digital Zoom actually surprised me and I found that it is quite usable. The image quality when recording in UHD and combining both the Extra Tele Conversion and the 2x Digital Zoom is pretty amazing given the focal length I was able to get to without losing any light.
I’m not the best at maths but a 300mm lens with the 1.4x Extra Tele Conversion and a 2x Digital Zoom gives you 840mm, all available at f/2.8! Having access to these type of focal lengths could be invaluable in documentary and wildlife shooting. It is important to note that I wouldn’t recommend shooting with the Digital Zoom enabled unless I was shooting locked off shots from a tripod, it’s definitely not a mode I would use during hand held shooting.
The 4x Digital zoom wasn’t so good – still usable in a pinch though if you really needed too.
HD digital zoom for massive reach
When testing the same combination of the Extra Tele Conversion and the 2x Digital Zoom when shooting in HD I found the image looked similar to that of using the 4x Digital Zoom when recording in UHD. The 4x Digital Zoom with the Extra Tele Conversion enabled in HD produced fairly ordinary looking image with noise and some artefacts, but again you could use it in a breaking news situation where getting the shot mattered more than the quality of the image. Again a 300mm lens using the 2.7x Extra Tele Conversion and a 2x Digital Zoom gets you an incredible 1620mm! All achievable at f/2.8 with the lens I was using.
Above you can see the modes where the Extra Tele Conversion function does not work.
GH5 Extra Tele Conversion: a unique opportunity to reach extreme focal lengths?
The Extra Tele Conversion mode on the GH5 is very impressive and Panasonic have certainly given news, documentary and wildlife shooters a real reason to look very seriously at the camera. You could only dream of being able to shoot at these focal lengths on other camera systems at the GH5’s price point.