I often hear, "You should only pick your wedding photographer if they use a particular brand of camera/lens and use full format." - Usually Canon or Nikon. Let's dispel one myth straight away, there is no such thing as full format! There's full frame, medium format, crop format and micro four thirds format.
Full frame is equivalent to the 35mm film format, medium format historically refers to the 120 size film format that was used in the Hasselblad V System cameras. In digital photography, medium format refers either to cameras adapted from medium format film models or to cameras making use of sensors larger than that of a 35mm film format.
Crop format usually refers to a smaller sensor than full frame and usually has a crop factor of x1.5 in the case of Sony, Nikon and Fuji crop sensor cameras and x1.3 or x1.6 crop in the case of Canon crop sensor cameras. So the lenses used are 1.3, 1.5 and 1.6 times the focal length in use. For example a 70-200mm lens on a Canon 1.3 crop body would equate to 91-260mm.
In March 2014, I was introduced to the Micro four thirds mirrorless system which was developed jointly by Olympus and Panasonic and are the only two companies that make the system. The advantage is all their lenses are compatible across the two brands.
Micro four thirds is x2 crop factor, effectively doubling the focal length of micro four third lenses - see below for more explanation. Panasonic cameras and lenses are branded as Lumix.
In the case of some lenses, they're branded as Lumix Leica, as the two companies are in partnership with certain lenses.
Leica lenses are synonymous with superb quality and very sharp images. Having said that, all the lenses I use are capable of producing high quality images, which at the end of the day is what you're paying for.
This system is smaller and lighter than the Canon kit I was using at the time but with equally good image quality especially when using professional lenses from Panasonic, Olympus and Sigma.
I dipped my toe into the micro four thirds system but kept my Canon kit at the same time. However, in November 2016, I finally took the plunge and now exclusively use that system and for my professional work, I use the following kit:
Two Lumix G9 cameras, one with a Lumix 12-35mm lens and one with a Lumix 35-100, these are your staple wedding lenses with a 35mm equivalent of 24-70mm and 70-200mm respectively and both with a fast aperture which will make the main stand out from the background which will be out of focus with the main subject pin sharp. With these, I can shoot from wide angle to close up portraits without "getting in your face!"
Strapped to my belt will be a Lumix GX9 which is basically a downsized G9 with a Leica 42.5mm lens with a fast aperture for lovely background bokeh. (Bokeh is a Japanese word meaning out of focus). This has a 35mm equivalent of 85mm, the perfect portrait lens and is a prime lens, which are known to be a lot sharper than their zoom counterparts.
Other lenses in my bag will be a Leica 8-18mm, Leica 45mm macro prime lens, Leica 200mm lens and a Leica 100-400mm lens - 35mm equivalent of 16-36mm, 90mm, 400mm and 200-800mm. I could literally stand across the road in the car park and still get a shot of you signing the register with the 200mm or 100-400mm attached to any one of my cameras.
The 8-18mm is perfect for wide, sweeping shots of the venue and larger group shots, the 45mm macro is another perfect portrait lens and for getting close detailed shots of the rings, cake decorations etc.
The 200mm and 100-400mm lenses, although not strictly wedding lenses, could come into their own if I was stuck at the back of the venue as I often have been due to instructions from the celebrant. I also have a 1.4x teleconverter for the 200mm, bringing the 35mm equivalent to 560mm!
As a backup and if all else failed, I have a Lumix GX7 with a Lumix 14-140mm lens, not a wedding camera/lens but I could shoot an entire wedding with this combination. The 14-140mm lens has a 35mm equivalent of 28-280mm.
The G9 camera bodies are dust, splash and freeze proof down to -10 as are the 8-18mm, 42.5mm, 12-35mm, 35-100mm, 100-400mm and 200mm lenses.
So if you're having a winter wedding, you can be safe in the knowledge that my cameras/lenses will keep going when your friend or friend of a friend with the entry level/cheap camera/lens will be running for cover.
My G9 cameras have dual memory card slots and I always save to both cards and I also have numerous high capacity memory cards, batteries and three flashguns, although I tend to prefer natural light as flash can spoil the ambient light and the ambience.
However, I will use the flashguns during the evening reception and usually off camera using a remote trigger to give more pleasing light than on camera flash. If you count the built in flashguns on the GX7 and GX9, then I have five flashguns. I have numerous spare batteries and memory cards as well
As you can see, every eventuality is covered with my extensive camera kit and this is something to consider when hiring an amateur photographer to shoot the most important day of your life. Will they have this amount of backup? You only get one chance to photograph a wedding so why leave it to chance by hiring an amateur who will probably only have one camera and lens!
If my images have a "blurry background" this is done entirely for artistic reasons such as the image of the bride and flower shot and the groom in the mirror. This is one of the benefits of having a lens with a fast aperture.
The same goes if I cut heads off, this is done on purpose to emphasise a particular detail such as the bouquet shot below.
I offer the services of a second photographer as an extra backup and to cover your wedding from different perspectives, something your friend or friend of a friend wouldn't even consider.