William Royer wrote:
Agree with comments about having her make selection decision. Wanted to emphasize the somewhat obvious point that —whoever makes the decision — it’s important that they look particularly carefully at the sizes of the lenses in the focal lengths they use. In several brands/models I’ve looked at (particularly for use when traveling) the size of the camera body was appealing, but the size of the focal length/speed of the lenses I used really made or broke the deal.
Equivalent lenses across formats can be very different.
Medium Format = VERY heavy
Full Frame Format = heavy weight and large size
APS-C Format = medium weight/medium size (native) or heavy weight/large size (if you use full frame lenses)
Micro 4/3 = light weight/small size
Some Micro 4/3 cameras are almost the same size and weight as APS-C bodies and the lighter full frame bodies, but the lenses are as much as 80% lighter. If size, bulk and weight are serious considerations, look at the smaller formats. The trade-offs of noise vs high ISO performance and depth of field equivalence are worth considering.
Here is a comparison I did a few years ago when deciding which format I wanted to use. It was just one of many deciding factors in my choice. I compared only full frame professional lenses with Micro 4/3, because that is what I would have used. I considered only the "professional's holy trinity" of fast zooms. I actually bought the GH4 and the two longer zooms, plus a 30mm f/2.8 Lumix Macro. I may add the newer 8-18mm f/2.8-f/4 zoom at some point, but haven't needed an extreme wide angle zoom just yet.
Panasonic Holy Trinity of lenses weighs 2.13 lb. or 965g 7-14mm f/4 10.58 oz. or 300g
12-35mm f/2.8 10.76 oz. or 305g
35-100mm f/2.8 12.7 oz. or 360g
That's not quite 33% of the Canon Holy Trinity and just 28.3% of the Nikon Holy Trinity of pro zoom lenses. Panasonic Lumix GH4: Weight (inc. batteries): 560 g (1.24 lb / 19.75 oz)
132.9 x 93.4 x 83.9mm / 5.23 x 3.68 x 3.30 in (excluding protrusions)
Canon Holy Trinity of lenses weighs 6.45 lb. or 2.928 kg16-35mm f/2.8 1.4 lb. or 635g
24-70mm f/2.8 1.77 lb. or 803g
70-200mm f/2.8 3.28 lb. or 1.490 kg
70D: Weight (inc. batteries): 755 g (1.66 lb / 26.63 oz)
Dimensions: 139 x 104 x 79 mm (5.47 x 4.11 x 3.09″)
Canon 6D: Weight (inc. batteries): 770 g (1.70 lb / 27.16 oz)
Dimensions: 145 x 111 x 71 mm (5.71 x 4.37 x 2.8″)
5D Mark III: Weight (inc. batteries): 950 g (2.09 lb / 33.51 oz)
Dimensions: 152 x 116 x 76 mm (5.98 x 4.57 x 2.99″)
Nikon Holy Trinity weighs 7.5 lb. or 3.409 kg14-24mm f/2.8 2.13 lb. or 969g
24-70mm f/2.8 1.98 lb. or 900g
70-200mm f/2.8 3.39 lb. or 1.540 kg
D7100: Weight (inc. batteries): 765 g (1.69 lb / 26.98 oz)
Dimensions: 136 x 107 x 76 mm (5.35 x 4.21 x 2.99″)
D600: Weight (inc. batteries): 850 g (1.87 lb / 29.98 oz)
Dimensions: 141 x 113 x 82 mm (5.55 x 4.45 x 3.23″)