I had a feeling that title would grab your attention. However, I’m not pulling your leg, I’m being totally serious. If you're saying “But Panasonic doesn't make teleconverters for their Lumix lenses!”, you would be completely right. However, you might be pleasantly surprised to discover that both of the teleconverters are probably already in your bag!
For those who may not be familiar with what a teleconverter is, think of it as a lens extender that turns your lens into a longer lens. The two most common teleconverter strengths are 1.4x and 2x. If you were using a telephoto lens that was 300mm f4, using the 2x you would end up with a 600mm f8. You can see that although your lens is now effectively twice as long, you've also lost two stops of light. Losing two stops (on a 2x) will really slow your shutter speed down, requiring you to raise your ISO higher than you might want. The other not so obvious issue is that the majority of cameras can't focus when f8 becomes the max aperture. In addition, quality teleconverters are not cheap and they take up more weight and bulk in your bag.
For years there has been a feature on many Lumix cameras called “Ex Tele. Conv.” (ETC). The feature is found in the Rec (red camera) tab in the menu. To enable it simply set “Ex Tele. Conv.” to “Teleconv”. The manual isn’t particularly clear and doesn't give this amazing feature enough attention. Therefore, I’ll explain what it is, why you’ll probably want to use it for certain situations and why it’s as close to a free lunch as you’re going to get!
ETC mode is not digital zoom. It is purely optical. Some cameras have a separate digital zoom feature, which I suggest you never use, as the quality is usually horrible at best. The only caveat to ETC mode is that you can't shoot RAW but only JPGs. Although I'm a RAW shooter, you'll soon read why I sometimes shoot JPG!
ETC works by masking the sensor. Think of this as the camera putting a piece of tape on part of the sensor and leaving just the centre exposed. There is no interpolation or image degradation happening. The JPG resolution setting will determine the amount of masking. More masking means a longer effective focal length (larger teleconverter power). On the GX8, if the JPG resolution is set to Medium (10 megapixels), you'll effectively be using a 1.4x teleconverter. If you set the resolution to Small (5 megapixels), you'll be using a 2x teleconverter. Since you can still use the Fine compression setting, 5 and 10 megapixel images are great for a number of applications. For example, either of these will be more than adequate for anything online and if you print your images, even a high-quality 5 megapixel JPG can easily print to 11x14” or larger (depending on quality of lens, focus, shutter speed, ISO, etc). When I first discovered ETC mode, you could say I was somewhat thrilled that I was able to turn my Lumix/Leica 100-400mm f4-6.3 lens into a 400-1,600mm f4-6.3 lens (2x due to the m4/3 crop and then 2x for the ETC mode) that autofocuses, or the Leica/Lumix 45mm f2.8 macro lens into a 90mm f2.8 and in Small JPG mode provides 2:1 macro magnification!
However, unlike using an external teleconverter the main benefits include:
1) You won't lose any image quality as you're not adding additional glass.
2) You don't lose light so your shutter speed can stay the same
3) Whether you shoot with the medium or small JPG resolution, your max aperture will never change, nor will the weight and bulk in your camera bag!
4) You can use any lens with Ex Tele mode, from fisheye to super telephoto, which is impossible with an external teleconverter.
A benefit of ETC mode that is identical to an external teleconverter is that the minimum focusing distance of the lens remains the same, which is great as you'll get more magnification from your lenses for closer subjects which can also allow for more working distance.
Some of you may be wondering why not just shoot RAW and crop in post processing. The following is a list of reasons why ETC mode might make more sense:
1) Your camera is metering for only the area the lens sees, not the whole sensor. This will most likely give you a more accurate meter.
2) Since you are only focusing on what the lens sees, it'll be easier to focus on your subject.
3) Your camera buffer won't fill up as fast with continuous shutter since the JPGs are 1/3 to 1/4 smaller than a RAW file.
4) You'll get significantly more images per memory card. Although memory is cheap these days, getting more images on a card during certain shooting situations might be useful.
5) Due to the masking, the sensor will only see the middle, or sharpest part of a lens.
6) You can make-up an extra stop or two to keep your shutter speed faster. For example, let's look at the Leica/Lumix 100-400mm f/4-6.3 lens to achieve a faster shutter speed. Instead of shooting the lens at 400mm f/6.3, you can enable ETC mode, set your JPG resolution to Small (2x teleconverter) and shoot the lens at 200mm f/5.1. You'll now be shooting with a 400mm f/5.1 lens with a shutter speed just under one-stop faster which can make or break a sharp shot in low-light.
7) You don't need to physically change lenses which saves time and also keeps more dust off of the sensor.
A few tips and tricks include:
1) You can assign the ETC mode to a custom function button so that it's always quickly accessible.
2) Considering your lens will now effectively be either 1.4x or 2x longer, you have to treat it as a longer lens and make sure you use appropriate settings (shutter speed, image stabilization, etc).
3) ETC mode can also be used for video.
So as you can see, ETC is pretty much a free lunch with some amazing dessert. The only tradeoff is that you have to shoot JPGs, which might be fine for some and unacceptable for others. Being a RAW shooter, I'm now shooting 90% RAW and 10% JPG.